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  1. #1
    YudLuz2's Avatar
    Join Date
    Jun 2005
    Flowood MS

    Ben's Secret Mods for Seadoo 951 and 1050 setups

    For the people that are interested in getting there Seadoo up to speed here is some good info that a have written over the years. Use this free info or contact me in building you a turn key boat. I don't have my XPL
    anymore but I'm still doing work on them.

    Had a few people wanting to view this again. I had saved most of my info on the building steps. I will be updating the section shortly on my latest testing. Rpms and speed has been droping off on my boat due to the summer temps but I still managed to run a 74.3 mph on link to see the video.) last Friday on a cool motor. Temps were around 75 degrees. Still don't have the proper prop setup, so I got a lot of work to do. More mods to come. The setback 12 vane pump is a keeper, I'm just going to have to speed money and time getting it dialed in. The Concord 15/20 and a 84.3 nozzle is the best holeshot setup, with no prop spin out of the gate. But the setback has a little more speed on top end. More later on this setup.

    Step 1

    Lets make sure we are starting with a fresh 951 engine. What we need to do first is basic maintance before we start any mods. Lets make sure are rave valves are clean. Make sure your filters are clean in each carb and your large single filter is clean too. Check the conditon of your fuel lines as well. While you have your rave valves off, lets inspect our cylinder walls and pistons. Check for scuffing on the pistons or the cylinder walls. We are looking for any type of water damage too, check the top of the piston for any type of deto looking thur your rave valves. Compression should be around 150 psi on a good running motor, around sea level. If any of these problems are not corrected now, you can bet it will bite you in the future. I don't recommend any mods for someone who doesn't know about working and tunning there ski. Use this information at your own risk, If you are not comfortable making these mods, leave it to a expert.
    Or you will end up with a blown motor. These mods are design for any 951 boat. XPL, RX,GSXL, and GTXL.
    Now lets start with my ski. Its a 99 XPL. I bought it used for $3000 two years ago in great condition. I bought it right after Christmas after being out of jetsking for close to 2 years. I had back surgery and really needed to get back in shape and the shock seat of the XPL really sold me. I have owned a 93,94XP, 97SPX, 701 Raider, 1100 Raider, GP1200, Kaw. 900ZXI,
    before I went to the 951 XP. I have always had friends with other name boats that I made the same mods to there boats. Sometimes it was just fun to make there boats faster than mine, just to give me a reason to make mine faster. If it was a good friend it was done free of charge, they only bought the parts. LOL
    The first day I took out my XPL it was around 40 degrees, at was around the first of Jan. I had my brand new GPS with me, and I was hoping for some 63 to 64 mph passes in the cold winter weather. On glass water my first pass was only showing around 59 mph. After playing with the trim I managed to get it to break into the 60's. But never saw 61 mph. Whats wrong with this POS GPS. Can't be correct. Man, did I go home with some hurt feelings. My last ski that I owned was a SPX with a VE 920 that would run 68 to 69 in the hot summer months with no problems. I was nearly 9 mph away from where I use to be. Do I give up? Buy a triple power boat? Hell no, I liked the way this boat handle and road thur the rought water. So what do I do? Buy a Level one Kit or two? and be like everybody else. No way, I wanted to be faster and that meant testing my mods against others to see which worked the best for me. My mission? To build a 70 mph boat using mainly stock parts. Other than one or two parts, my boat uses all OEM parts, with a few small changes in certain places that I will cover. In other words they are no one off high dollar parts that can be found on this boat.
    Now my first step was to do the basic maintance stuff I started talking about at the beganing. I then did a fresh top end with new OEM pistons. You never know the condition when buying a used boat, so thats were I spent my first money, like that we knew it wasn't going to bite me in the future.
    And I then purchased my first mods for my boat for $145.00

    Stage 1 You guessed it

    Air filters and jet kit.

    I recommend the Prok filters. They fit on your stock carb setup very nicely. You save a little weight by getting all of that junkie stock air box out of the way. Weight, I will be saying that word more in the future. Little here and there, and you can have a surprisely lighter boat. Remember I'm 6'3 235 pounds, and it takes a lot for a boat to get me out out the water quickly. So I have trimed in many areas. The jet kit that I recommend comes from Bill O Neal. WaterCraft Magic. I recommend parts from Bill and Mel Miller. The only other person that I recommend is from Dean Charrier, Team Dean's. All of these guys have been around forever and they know there stuff. Jetting is 85 lows and 167 mains with 2.3 needle and seats with stock springs. This jetting works great in Mississippi and probably works good any where with slight tunning. My lows were set at 1 1/2 turn out and highs were set at almost close to 1/4 turn out depending on weather conditons. I love the stock carbs, once you tune them you don't have to readjust them all the time like aftermarket carbs. These same carbs, with some tweaking are used with my 70 mph boat and I still use the stock oil injection. So, unless you are scared your oil injection is going to fail, I would recommend just leave it own. Nothing like gas and go. And it works fine for me, even turning 7500 to 7600 rpms. I also recommend you installing a primer kit now, or a little later when you are making a little more power. Don't worry about the so call 3/4 lean spot everyone talks about, tuned correctly its something you don't really worry about with these mods. I have ran my stuff a 3/4 throttle forever with no problems. More carb mods to come once we add more power. These mods made my XPL run a nice 63.5 to 64 mph in the cold weather with a fresh top end. Please note all my speeds are average speeds over a 3/4 mile run. The ski was turning 7150 rpms and would hit the rev limiter every now and then due to the cold weather conditions. Big gain. Next setup. More compression and buying the correct head.

    Step 2

    High performance head. I'm doing this mod next in line because the impeller that I will be picking works best with a increase in compression due to its taller size.

    While many after market heads are available, My favorite one is the Mel Miller head. Not only is it nice looking but it is top quality. The Buckshot, and Rossier heads are about the same, some
    are just a different name or color. No heads are bad, some should only be used with certain mods or what they were design for.

    The Miller should be run with 49cc domes. This will increase your compression from 150 stock, to around 165 psi. I found that a squish of 55 thous. works great on this setup. The jetting that I gave in Step 1 works perfect for this head. And very little if any adjusts are needed when you install the head. Most people have a very slight rich condition with the stock head, it is mostly notice during no wake zones.

    I compared this head to a stock milled head. The head was supposed to be setup for pump fuel. But I question that, since the compression jumped from the stock 150 to around 185 plus. The compression check were always done with the same guage. Squish was set at the recommended 75 thous. from the head supplier. The head was tested while using a Solas 15/20 Concord. What I found was the modifed milled OEM head was very close to deto with this setup. A increase amount of fuel was needed to stop the pinging and deto in the mid range. I think this is obvious since they recommend using 170 mains. There was a slightly advantage on the low end but the added fuel that was need to control deto made the top end suffer almost 100 rpms over the Miller setup. Everything possible was done to try to make the OEM mod head work better. Changing timing by increasing and decreasing the base timing and trying different jetting sizes, adjusting TPS, and even going back to the stock prop. I did a full two weeks of testing , even deto the rear cylinder enough to have to replace it before I could continue my next mods. I never could get the peak rpms with the OEM head I was using. So I finally settle for the Miller setup as what work best for me. Remember OEM heads do get cut different and could perform different based on who and how they are setup. But the true way to build a setup is with a head that was design for
    a modifed motor. Thats my you see Miller designing these heads for the public. Since I did mention the TPS sensor which comes on the 99 models and above. Please don't touch it if it is working correctly. They either work or they don't. And if they are not working, beleive me you will know. A simple test, is to unhook it, and see how slow your ski takes off out of the hole. LOL They can be checked with a volt meter if necessary. Another advantage in using the Miller Head, is cost. You can inspect your top end without buying that $38 head gasket. I have found a local supplier that sells the orings for aftermarket heads for like .15 cents a peice. Some people have been using a 46cc dome in the Miller head, with a larger squish clearance. This is increasing the risk of deto but I would rather use the 49cc domes in case you need to put some 89 octane in your boat since there is no 93 available on the water. I have found that a lot of compression is not needed to have a strong accelerating 951 motor. I like the idea of increase of timing over this method. I will talk about this in my later mods. I got my used Miller Head for $150. There around $300 new, so this might be a item you want to shop around for on the net. You will see a nice performance gain in acceleration all the way through the power band, and with a larger prop you will see a slight gain in mph. At least .5 mph.

    Step 3 Buying the correct prop and what pump to use. This is probably
    your most important item that you will buy for your boat.

    Step 3

    The best prop for your boat is a Solas 15/20 Concord. Period.........
    Why? Because its the best all around prop. Some props will run close to it in top speed, but never out performs, and nothing and I me nothing will give you better mid range acceleration. It is the best king of hill drag racing prop out there. I still use this same bone stock prop on my 1050 big bore.

    This prop really hooks well out of the hole, the Scat swirl does this best, but gives up speed on the top end. The stock swirl prop will never give you the mid range speed that the Concord will deliver. It normally will cost your rpms to drop 150 two 200 rpms. But speed will still increase to 1 to 1.5 mph over a bone stock prop. To get the most out of this prop, with the currect mods listed, you need to turn it a min. rpm of 6920 rpms. With this prop you should now be running a easy 65 mph speed. I have turned this prop in colder conditons with these mods as much as 7000 to 7050 rpms. High 65mph to breaking the 66.5 mph speed has been done with my XPL. This mod should not be done first, due to the fact I bone stock motor would only pull this prop approx. 6640 rpms. Lets also remember there are different Venturi nozzle sizes that come on different 951 hulls. A 85.5mm Venturi can be found on many XPL and the 87 sizes can be found on the GSXL hull. There are some other in between sizes out there too. That does make a slight change in peak rpms, giving the GSXL a slighter faster top end due to better hull for smooth water speeds. I recommend the 85.5 Venturi. The exit steering nozzle is close to 90 mm on all 951 setups. The 97.5 GSXL does carry a different pump, prop and nozzle setup.
    So, What is the best pump to use? The stock bronze pump in the 98 or 99 models or the 2000 and up plastic style. I have ran both, and back to back, back to back, back to back, back to back testing. You get the picture. In the same day the plastic pump wins out while testing 3 different props in each pump. The plastic pump was nearly 2 mph faster with some props, verus the bronze pump. The plastic pump loaded the motor less, than the bronze pump. The added 100 to 150 rpms over the bronze setup let the plastic perform better in speed and acceleration. There was also a huge weight difference between the two. But it did feel like the extra weight helped the boat stay hooked up better in the choppy water, Might be the reason why some racers perfer this pump over the plastic. Installing screws in the wear ring is a must on a 951 boat, or you will end up spinning the wear ring if not. My horsepower would even create more problems in this area if not done now. The newer plastic pumps some from the factory with them already in place.
    I don't recommend cutting the back of the blades off the Concord, It will cause to much prop spin on a high performance 951. You can slightly bend the prop if you need to get the prop to work a little better in your rpm range. I won't hurt the prop if done correctly. My sources also tell me the Concord has gone through 3 different changes since it was first produce. I beleive the first ones were slighter bigger than the ones that are produced now. I beleived when Solas saw the newer style plastic pumps come out in 2000 they made a slight adjust on the prop then too. So like any prop they will vary in size. I have ran 4 different Concord props and they all worked well. But they did vary in rpm, but speed was about the same. I have also ran the Nu-Jet 6.0 and 6.5. The 6.0 gives good top end speed like Concord. But doesn't have the acceleration. It is also a prop that is hard to turn. So you need a lot of power. Hooks good out of the hole for a NuJet. The 6.5 is to big, do't even try it. If you got the HP it does gives good top end, its like the 6.0, just a much bigger prop.
    I have also tried the 16/20 Concord. Did not like it. Was much bigger than the 15/20 and just put to much load on the motor. To be honest this is one subject that we will never figure out. We will always be looking for something better. What might look good on paper, might work like crap on the water. It always seems when you send a prop out when it gets back it never is like you want it. Thats why I like the 15/20, just stick it on and ride. Price new around 175.00 can be found used for around $100

  2. #2
    YudLuz2's Avatar
    Join Date
    Jun 2005
    Flowood MS
    Step 4 More cheap mods and loosing a little weight
    Posted: Fri Jan 16, 2004 3:33 am Post subject:


    Step 4

    Lets do a few more cheap mods before we spend anymore
    of the wifes money. LOL

    The first thing that comes to mind is we need to get rid of a little more weight and get that sound baffer out of the boat that does you no good. By removing the baffer (the big black plastic box talking up so much between your water box and exhaust outlet) we are saving us some pain
    in the future. These babies will crack or get holes in them over time, I've seen a few melt away do to lack of water running thur your exhaust hoses. Every had a water line pop off going to your pipe. It doesn't take much to get this baby. Well for around $30 its gone and you save a little weight and you make more room in your hull. Hint: good place to hide a NOS bottle in a XPL But I actually have a small boat paddle that I mount there. You never know when you might need it. Dead battery, cables, no gas, blown motor, broken pump, starter, fuses, fuel lines, plugs,
    spark, you name it, sooner or later it will happen. The correct parts to bypass this feature can be order from a older 98 model ski that doesn't have this feature. Also I believe they don't have them on the ones across the big ocean from us. Now, what about all the rubber wrapped around your water box, its a pain in the a**, but rip it out. This stuff will get wet and when removed while still wet, weighs almost 10 pounds. Hell one of those high dollar carbon fiber hoods don't save you that much weight. Well since I did mention carbon fiber, I you do have that much money then go ahead and spend that money on your hood, and rear storage cover, and send me a set too. LOL
    I also like to look at the way the air comes in on the XPL. Make mods anywhere that can help you increase your airflow to your motor. On my ski I trimmed the hoses up front and the two in the rear about 1/4 away from the bottom. No need for the air to go straight to the bottom of the hull, thats not where the carbs are located. Underneath your seat is a rubber plug. Its there to get to your pickup in your gas tank. Leave it off. It helps get more air to your engine. And you never have to worry about gas fumes building up in your hull, since its breathing all the time. Its a good idea to put it back in if your going to store it for a while. These mods only make a very slight increase in noise. But if your motor turns the rpms like mine, it's a sweet sound and you could care less. Ever notice how many tie straps you will see on these boats, they look like there a foot long. Trim them up nicely, hell you might save 2 pounds. But
    you get the picture, clean everything up, make sure your boat doesn't have extra water in it, and its nice and clean inside your hull like it is on the outside of it. You will never see my boat dirty on the inside, I take much pride in it, I even take the time to wipe down each part before I put the motor back together. LOL
    Here is a little hint about comparing EGT's of your boat to someone elses boat. Don't do it. To many things can make a difference. For instance the 98 XPL has a larger water outlet at the rear of the boat. Sure it looks the same as my 99, but when you remove the hose you will see a restrictor at the pump that cuts down on the flow of water going out the back of your boat. What does this do? On the 99 model it will keep the water in your pipe a little longer, normally keeping the pipe cooler. That means different EGT's. I like to remove that hose and install it on the larger outlet that the bilge pump usually connects too. You will need to down size one hose and upside the other on the ends only to make the switch. I also drill each fitting at the stock pipe to allow the max amount of water to exit the pipe. This will increase the temps on the stock pipe, changing the sonic wave in turn giving you a increase in peak rpms. The stock water regulator works great with the stock pipe. You will need to adjust this valve depending on water and air temps. So your summer settings will be different based on your fall settings, or you might be missing that 50 to 75 rpms you once had. I should have noted this first but you must buy a digital tach to be able to tune your ski correctly. Buy a nice one if you can. The commerical tiny tachs work great for around $69. I run the Pet 2100DX Why? Because it's the best and I'm a tunning freak.
    Since we are on a low budget, its time to do some porting. You don't need to be a master to do some cleanup work on your stock exhaust manifold and exhaust pipe. If you want to add a little more on the top end, add a exhaust head pipe from a 97 1/2 GSXL. There white and bigger than a ported stock pipe. Now paint it black so it will look like your stock OEM pipe. Your friends will never know. Trust me on that one. You will not need to change the lower half of the pipe, there all the same on 951 motors. The head pipes do vary slightly on the XPL, RX, GSXL, and GTXL. The difference being the size of the water ports where your exhaust manifold bolts up too. Which could also create different EGTS on a stock pipe boat compared to another unit. I would like to say a EGT is a nice setup to have, it will not get your boat dailed in from blowing up and they should not be used to tune your boat. Thats your job, but it is there to (fine tune) your boat. That means getting the last possible rpms out of your motor. It can save your motor sometimes when something goes wrong, but I would say most of the time your already stuck with a blown motor before you realize there is a problem. So its not going to save your a** every time. For the record I have never had a EGT gauge on my boat, nor do I need one to dail in a motor. Remember they didn't always have these nice little toys.
    Step 5 next. Ride plates, Intake grates and handling
    Posted: Sat Jan 17, 2004 3:52 am Post subject:


    Step 5

    Its time to make a decision on if you want a great handling machine or a fast ski. I think you can have both with the XPL. Remember a lot of these mods with scrub off a good amount of top end speed. Something you have been spending money on all year. So don't do it, there's a reason why I like the stock stuff, It works pretty dam good.

    First lets look at the sponsons. They will make your ski turn like a dream machine. I'm still running the stock sponson on my ski, the ski turns well enough for me in stock form, I'm more of a straight line guy so its something I normally do last when I get bored. The one thing you must watch is what type you install. You do need to watch how far down the sponson will hang, and determine if they may scrub off speed. Usually if they do its a small amount. I would love to hear from somebody that has some back to back testing in peak speed numbers from the change over.

    Next on the list is intake grates. If you want to maintain the best speeds, the only grate that will do that is the stock one. By doing some trick grinding on the back side of the grate it can give you additon .5 mph if you know what you are doing. Removing the grate and running without one will slow you down around 1.6 mph. Its not like the X4 hull, got to have a grate on it. I have also tested a one off half stock grate that I design myself. Speed still did not match my orginal grate. I think a aftermarket grate is a waste on money, unless you are a ocean rider or a bouy coarse rider. Well let me just say, there have been some World Champion trophies giving to guys that run a stock grate. This is on a XPL hull, when that baby comes unhooked its usually because the whole boat, pump is out of the water. I can honestly say I have never lost to any boat
    on my XPL in rough water using the stock grate. That includes 75 to 80 mph GPR's. The thing about those boats they easily loose 10 to 13 mph when they hit choppy waters. There setup for smooth, but the XPL will always maintain there speed through the choppy water. You just got to hang on.
    Here are my results testing with a worx grate verus my stock tweaked grate. The hookup out of the hole was much better with the worx grate, mainly because its loading the pump much better. But a really didn't see any gain going through the chop. And in light chop I did loose speed too. The day I was testing I ran across a Triple pipe Ultra 150, I had ran him before and pulled away from him in glass water. I was having a harder time with this ski in light chop, and I knew I should have pulled away from him but I was barely beating him. After making a quick GPS run, I couldn't believe my ski had just lost 1.4 to 1.6 mph with the Worx grate. So many people talk about such great mods this and that is, and here is the proof that most people don't have a clue. expect this with almost any aftermarket grate.
    Ride plate You got to be a slick salesman to sell these things. On the XPL the R&D ride plate will loose a tad over 1 mph on glass water. It's kind of obvious since the plate is slightly longer. I also tried one of those so call trued ride plates. Lost well over 1.5 mph. It had some grooves in the plate when I sent it off, but it came back the same way. So what the hell did they do? I turned around and bought a new one and pick most of my speed back up. But I was still around .3 tenths short on speed. So do this mod at your own risk. Might work, might not. But it did improve the handling, but I don't give a dam about that, the XPL handles just fine for me. The main thing that helps the handling is blocking off the speedo plate, so it will be like the other side. Makes since? Well I can tell you a little trick. If the front of the speedo (stock speedo sensor) is hanging down one hair below your ride plate it will make it handle bad. Where the ride plate has a opening for the water to come thur that small channel into the channel of your speedo gear, IT MUST BE FLUSHED WITH EACH OTHER. I first notice the problem when I installed my new ride plate and a brand new speedo sensor. Yes, I like seeing my speedo go past 70 as I'm leaving my friends behind. LOL My speedo hung down just a tad more, no big deal right, well I went out and knew right away a had lost some speed, but hell the only thing I had done that day was install a new speed sensor. Then around 66 mph the left back corner of my ski completely lifted out of the water, planting the nose very heavy into the water. It got real scary quick. Back to the boat ramp, I notice the only thing it could be was the speedo, but how, I had some washer that I shimmed the speedo plate up, just enough to see if this was going to make a difference. It did but I could still feel the boat trying to plow the nose of the boat. After a trip home, I bolted the speedo back down in the slots. and took a file and grinder and went to work, until both parts were match up perfect. The next day I was very happen that my boat was running correctly again. Point made is to never look over small items. When I make all my GPS passes they are done with one hand holding the GPS and one hand guiding the ski. So I guess you know my boat rides solid as a rock with no stable issues at 70 mph. Guess it would be nice to have a GPS with peak speed, but I only believe in posting average speed done over a 1/2 mile run. No chances for spikes. I use to only test with a radar gun, but its kind of hard to get a friend to do so much testing with you, so I have found if done correctly a GPS is your best friend. I have tried shimming the ride plate, but I have always lost speed. My ride plate had no shims from the factory. Very important. Keep your ride plate sealed. I use the Right Stuff to do the job. It can be purchased at any Auto Zone for around $12.95 I have been told by Bill O Neal the 97 XP ride plate will give the 951 boats more top end, by getting the nose out of the water more. It is a different part number and makes sense. I have a brand new one to try when I get a chance. Will report back the results. If it doesn't work I will be making a one off speed plate to try from the setup. Will let you know.

    Step 6 Reeds and intake manifolds and addition carb mods.
    A little money spent but well worth it.
    Posted: Sun Jan 18, 2004 3:16 am Post subject:


    Step 6

    Aftermarket Reeds. Good or Bad? Well I only recommend one and those are the Rinaldi reeds. Thats what I have been running in my big bore motor for over a year, without any problems. Some common problems people are reporting that other aftermarket reeds tend to break after a very short time. If I remember correctly I paid $250 for my reeds and Team Deans spacer. I felt it was a very small gain in performance but something that needed to go with my big bore motor. My orginal stock reeds look great when I removed them, so I can say that there is nothing wrong with them at all, and they do give great performance as a oem part.
    So no need to run out and buy a set, if you need to spend your money on other mods first. If you install them on your stock intake manifolds they work just fine. You will need to grind down a spot (small block) on each side of the manifolds so the reeds will set down flat against the spacer. No big deal with a dremel. You also need to use a little longer bolts because you are using a spacer now, some spacers (miller) verus others are thicker. This is allowing your reeds to be pulled away from your motor. The Spacer moves the reeds back away from the turbulence of the whirling crankshaft and provides longer reed life while smoothing out the power of the Sea Doo 951 motor. Bottom line is there suppose to be good for around 5 HP, which might add up to around 50 rpms after some tunning.

    Intake Mainfold Since I'm still running stock oil injection I decided to go with a R&D mainfold. They have the holes where you can slide your stock oil injections right into place. They work well, and I would either buy them or the Miller setup. The R&D does have a thicker manifold putting your carbs farther away from your motor. Milling down the manifold, it can be made the same thickest of the Miller one. Something I will be doing soon. My peak rpms didn't increase with the R&D but it did hit harder out of the hole. Improve in mid range, this is due to the way the stock manifolds are made. There is a dead area in the stock manifold, it starts out small then has a large opening and then gets small again. The Miller stays the small all the way through the unit, hence no dead air to deal with in the carb system. Getting the carbs closer the the reeds are better acceleration and throttle responce. You will need to drill fittings for the Miller if you are going to use your stock oil injection.

    More carb mods,
    Nice gains can be made by smooth boring the carbs, in the past on Yamaha watercraft very large castings could be found in the mouth of the carbs, restricting your airflow. Well on the Seadoo carbs very little restrictions can be found. There are only two spots that I removed in my carbs, but every little bit helps. Pay close attention to your carbs gaskets to make sure they are matched up and don't overhang blocking your airflow. Next, Its time to make your ski run prefect on every launch and never load up on you again. Its time to remove those accelerator pumps. I recommend you disable them first by bending the accelerator arm over so they will not activate. So if you don't like the mod, you can rejet and simply bend the arm back over. But everyone that I have talk too on this mod, loved it without the pumps and they would never go back. Your throttle responce is 100% better, and your ski takes off out of the hole every time. With the pumps in place your ski will never get the same amount of fuel everytime you hit your throttle out of the hole. If you take off 8 times in a roll with the pumps in place your ski might leave perfect 3 or 4 times if your jettting is very close. Those times your ski doesn't leave correctly , it could cost you a race. Holeshot is one of the most important thing to consider when drag racing. Don't blow it off the start, so many people that I have raced never had a ski that worked well out of the hole. I was always stopping for them till they got a good holeshot. My ski always had the instant responce time after time. There is no comparison between the two if done correctly. Thats probably my biggest advantage over my competors. A perfectly tuned and jetted ski, it makes a night and day difference. Once you get it dial in you can go ahead and remove a lot of the accelerator pump equipment on your carbs, it cleans things up very nice and helps you get to your low and high screws much easier. If you are currently using 85 lows with the pumps, switching to 95 lows without the pumps should get you right on the money. I have had other people try the 90's or the 100's and they both settled on the 95's. I have had one person tell me, do to some mods made by another company to there carbs they didn't perform that well without the pumps. So there is always a Catch 22 to look for. I have been using the 95 lows with my 951 and 1050 big bore setup, with no such thing as a 3/4 lean spot spoken by so many people. I guess if you want to run a 185 to 195 head, well hell you might just have that problem.

  3. #3
    YudLuz2's Avatar
    Join Date
    Jun 2005
    Flowood MS
    Step 7 Timing, MPEM mods, and talk about aftermarket rev limiters
    Posted: Thu Jan 29, 2004 5:51 am Post subject:


    Step 7 Timming and modifed ignitions

    It's time to move forward, and this next mod will be required to have for the final mods you will be adding to your boat. You have two main things to pick from, a modifed reprogram MPEM,
    and Micro Touch Rev limiter and timing control, or a advent ignition. There is also one from R&D. There seems to be a problem from the one from R&D, I think the manufacture never produce any units, I tried for many months to get one, with no luck. That leaves Micro Touch, good company with good people to stand behind there product. I have tried there unit on my 99XPL. Nice unit, you can change the base timing, timing curve, retard rate, adjust the rev limiter and run two water silonds. Many custom settings are built into this unit. The problem, high cost, having to cut and splice into your two main wiring harnesses. Install time, and not something for a novice to do. Well I guess if your a novice you shouldn't be playing with these settings anyway. LOL Cost is $600 for a new unit.
    The main problem is none of the timing curves are any better than the stock curve on the stock Seadoo MPEM. Thanks to Seadoo they already have done a excellent job on the 951 motor boats. I have notice a slight hesitation or delay using the Micro unit, I think this is mainly because of the unit still using the stock TPS sensor. It requires it to gather more information before making is decision to send this information to the brain. A lot of things are being considered, throttle position, load on motor, rpms of motor, to name a few. Its still in what they call soft mode. The decision of the brain of the Micro unit may not make the same decision ever time. So your great holeshot, might not be that same everytime. Performance is sometimes lowered using this method. A hard mode is the best way for performance, which does away with the TPS
    sensor. (This is not found on the 98 XPL) This is what makes the reprogram MPEM stand apart. The cost is only $300, and you don't need to cut any wires, it just bolts back on. And it doesn't effect your standard features in which you might want to check hours, base timing, all with your standard seadoo programer found at your local dealer.
    The improvements are done by tweaking the stock curve based on what mods are on your boat. Enter the world of tweak reprogrammed MPEM's.
    These are done by removing the MPEM and sending off to someone. Dean at (Team Deans) does a nice job at making these units better. His timing curve works well on all the mods I have made to my boat and will set the rev limiter at any rpm you desire. For a reference mine is set at 8499 rpms. Seems high but when your boat is running through the chop, rpms tend to climb. This is one of the main reasons a XPL will slow in the chop, your probably hitting the rev limiter and don't even know it. Hell I didn't even know it on smooth water the first time my boat hit it, with just a few bolt on mods. And in the rough it was all over it. So you will right away see a increase in speed in these conditions. Its nothing to see my stock tach hanging around 8000 to 8100 rpms going through the choppy water. One might think the motor wouldn't last, be so far not a single failure do to high rpms. Earlier I had spoke of a hard curve, which most reprogramed MPEM are done, they don't use the TPS sensor, so it only has one set of values to choose from, unlike the other one that has two to choose from and other factors to determine that final decision. With the information already program in the computer it can make a quicker decision, (yea these things are making a million a second already) lol, but allowing the hard values already plugged in, it will always have a more consistant performance. For the average Joe, all we know is that we grab a hand full of throttle and we go. LOL But, ever wonder why it doesn't have that great holshot everytime. Its not always because of carb tunning. One nice thing about my MPEM is it was setup to use the stock carbs, and no water injection is necessary on the coffman pipe. Less stuff to have to worry about. And those stock carbs are nice, they can be set, and not even have to be touched the rest of the year. You will see that most aftermarket carbs will require a lot of adjusts everytime there is a change in the weather. Drive 600 miles to a different state, and those stock carbs probably won't even need adjusting.
    My MPEM was setup with two addition degrees of timing on the bottom up until 7100 rpms. Where it starts a retard of around 1/2 degree per 100 rpms. Design for pump gas setup. There are other race curves, I have tried a 5 degree advance unit that really kicks a**, but requires race fuel.
    Most of my ride time is done with the MPEM advance another 4 degrees on top of the orginal setup. This is done by moving the base timing that was preset at 5 on the Seadoo programmer. (Good to verify this by going to your local dealer. Programmer number 5 on the MPEM stands for a ignition timing correction of -1 degrees. So your base timing could still vary based on what the good old timing light reads. Here is your timing correction chart to go by on the 951/1050 motors.
    2 = 3 degrees timing highest setting of advance
    3 = 2
    4 = 1
    1 = 0
    5 = -1 degree timing
    6 = -2
    7 = -3
    8 = -4 lowest setting

    For your reference my unit is always ran at least 2 which equals to 4 more degrees advance from the orginal set point. So how do I get even more? Well thats a little trick. When its time to go race the big dogs, I will add a little more race gas and add two more degrees of timing. This is done by drilling larger holes in the mag cup. There are six holes with bolts that have very large oversize heads on them holding the mag cup in place. You will need to take a drill bit and bore these 6 holes out larger. Its no problem going up 3 to 4 size larger drill bits on each hole. Your head of your bolt will still cover the hole, but it will allow you to rotate your mag cup clockwise up 2 mm. For each mm you are turning the mag cup, it will add additon 1 degree of timing. This is done by some racers that like to cheat in the stock class, to get advantages over the other riders, and its something they can normally get away with. Two degree can easily add a full 100 rpms on the top end and a lot stronger acceleration. Thats how I setup my motors, lower compression but lots of timing. So if your running a 190 psi head, your already on the edge of deto, and there's no chance in hell you can add anymore timing, unless you want to start pouring race gas in a nearly stock motor. LOL
    Remember there is a reason why a have choosen my mods and how I setup everything on my boat. Its all about the right combo. Everything matters. Thats why we don't mismatch parts, and I only test one item at a time.
    So how much timing is to much? That is so easy to figure out on the 951/1050 motors, its almost to easy. The key is knowing your motor, listen to what its telling you, this is probably the hardest thing to learn. This motor will give off a knock or ping to let you know when there is deto going on. If I don't hear it, then I don't worry. But you may never learn to use this method. I never go out to do some tuning with another boat, you must be where you can hear your motor and not someone else or some background noise that keeps your from knowing whats going on. A seat in the pants feel, that you get from your ride is the next best thing. Something don't feel right, lazy feeling, weird noise, its time to back out of the throttle. Knowing this will make you one of this best tunners out there. Sure looking at the EGT's are nice, but the other stuff is more important. If you know there is deto, than you can stop it before it takes toll on your motor, If I'm going to be running a setup then I expect it to be able to at least make a 1 mile wide open throttle pass safely, even when tweaked on the edge for max. performance. Removing your head and checking piston wash and signs of deto on the outer edge of your pistons will give you a lot longer engine life. Timing mods on 951 motors are done probably by less than 10 percent of the owners, why not more? They are scared and probably have enough problems already. LOL But the main reason is there setup doesn't allow it. But just because that slick salesman sold you those parts don't mean its the best combo to use. There in it for the money, they sell the parts and mods to make them the most money in there pocket. Thats when I turn and go the other direction. I have always done stuff different based on what I just stated. Bottom line, there is always a better way than what the slick salesman is trying to sell you. And I make it my business to know.

    Step 8 The most important one of all. You got all the parts now that you
    need, whats your next step?
    Ported 951 motor? Piped stock motor? Or Big Bore 1050 motor?
    Your porting answers to your most important questions. Learn about actual porting gains, and who to use for those services. The answer is easy. You are about to learn more than you need to know.

    Back to top

    Posted: Mon Feb 02, 2004 1:28 am Post subject:


    Well I thought I would give at least a update on my boat tonight. I have tried two other mods on my boat. One, a new ride plate from a stock 97XP. And two, a modifed stock head done from Mark at Cal-Jet on my 1050 motor.
    Well the head was a nice gain, it was making a lot of power down low, temps were 60 degrees outside and sunny. Wind was blowing, but I was able to get some decent runs inside a small channel. On this flat type of water, my boat normally runs 1 mph slower than my other location. The boat seems to like water that has slight ripples to it to get the nose out of the water a little more, XPL hulls are just not great smooth water boats from the factory. They like to dig in and hook, which is what they were built for in rough water conditions. My other location is over a mile long but the wind was kicking to hard to make in passes there. So I made some short passes and lanches out of the hole. What I found was the boat was having a problem hooking now. It was spinning the 15/20 Concord pretty hard, peak rpm recall showed the boat hitting 7700 rpms out of the hole before it got on plain. It was leaving hard, don't get me wrong, but got to made some changes. Probably smaller nozzle since were dealing with colder conditons. I did play with the throttle a few times to give the prop time to hook and it did hook nicely. After riding around 10 minutes It was time to make some GPS runs. I only had around 1/4 mile to make my runs, there were a few boats fishing on the end, so I didn't want to bother them. My first pass I started from around 20 mph, I had to make a adjust on my trim, and by the time I got my eyes back on my GPS I was already at 70.1 mph in just a few hundred feet into the run. At seemed the boat was accelerating quite nicely with the new head. Once the boat hit 70, I was having a hard time keeping the nose down. The boat ran 5 passes back to back over 70. I started making a few adjustments, rpms fell off a little due to the back to back runs, but I found that my boat worked a little better trimming down 1 notch. It was still climbing at the end of my next run at 70.6 mph. I hope to be over 71 mph when I go out and do my next runs in my location that I get my best speeds. After this pass the wind starting blowing harder, and it was really hard to keep the boat perfectly straight, so I hoping for a improvment next time out.
    The ride plate seemed to help around 1 mph, considering I have ran these rpms before, at a lesser speed before on the glass water. So I think this is a nice gain on glass water. A can tell a big difference in how this plate is made than my stock one. Lighter, and the rear is angle up in the rear to get the nose up more. I did have to tweak the opening it the speedo gear and use some right stuff to fill a small gap. It was a quick install, so I do need to go back and make some improvements. The small 84 nozzle that I want to try next should control prop spin better and increase peak speed.

    Back to
    A quick update one my new head. The head has a better cut and a more aggressive squish radius. The Miller domes that I was using were only 49cc but they were cut for the Miller Wisco pistons. I'm using a semi flat Rotax piston that requires something different. I will be trying in the future some special cut domes, for the Miller head for these pistons. I think they start off as 42cc before they are redone. The OEM head only had 70 thous squish compared to 50 thous on my Miller domes. But the Miller domes are not as aggressive cut, still didn't perform as well. The large 70 squish is mainly due to the fact the Oem uses a special cut 951 stock head gasket, where the Miller using no head gasket, just oil rings.
    I will be increasing the squish clearance to at least 60 or lower, by using a thinner comestic 1050 head gasket or a 3 or 4 hole base gasket to tighten things up a bit. Should be able to add another 5 to 10 psi of compression in the process, making my prop spin even worse.
    Speaking of compression, I don't have a clue, my starter,bendix gear has pretty much crap out, and barely starts the motor, so I can't get a reading on my gauge. The OEM head should be around 13.5:1 now. I only mixed 1 gallon a race fuel to almost 3 gas of pump fuel with no deto. I also was running full water to my stinger with no jet, which increase deto too. So I believe I could back off some timing and hard jetting and run this head with 93 octane. But considering how bad some stations gas is compared to others, why take the chance. I hope to give a update on the nozzles next weekend. I didn't mean to get off track, but I will be going back too posting information on the nest steps you should take.

    Whats next? You got three things to pick from. I will list them in order.

    1 Big Bore setup
    2 Coffman Pipe
    3 Ported 951 cylinder

    Do the big bore next. Why? Its a kick a** setup. My Big Bore with a completely stock bottom end kicked a lot of butt with just using the stock OEM pipe. It can reach speeds above 68 mph and accelerate like a animal. Its as reliable as a stock cylinder setup and should last a good 100 hours before a rebuild is required. It runs on pump fuel and will allow you to beat most of the Coffman pipe boats out there on the lake. I never lost any type of drag race to any twin pipe RXX or pipe XPL while using my stock pipe. Now don't get me wrong, there are fast boats out there that could take this setup down, but those boats are very limited numbers. Nice thing about it, looks completely stock, using a modifed OEM head you could fool anyone. Its the ultimate sleeper. All the mods you have now work perfect with this setup. Since there are two main kits available, Miller Big Bore setup, Team Deans and Cal-Jet Rotax bigbore setup. We will talk about what setup works best and which has a big advantage in price. Mark at Cal-Jet is the Rotax Racing dealer and most all of the parts come through there center. They have cylinder and head mods available just like Team Dean. My setup is the Rotax one from Dean, and I began last week using Mark's modifed OEM head on my race setup. These kits are mainly based off of Franko at Seadoo Rotax Factory Racing. We will talk about this setup later, I just wanted to touch a little on each subject to point you in the next direction. There are no negatives using this kit, price is good, its reliable and you get a lot of performance for your money.

    Next Coffman pipe

    If you are just going to bolt a coffman pipe on you will probably be in for a surprise. Why? I have seen many coffman boats run poorly, some barely faster. Others blow up quickly. Octane requirements go up, and if the boat is not prop correctly you won't have speed or performance. Having the boat off in jetting or prop size just a little can make you have a boat that doesn't perform to your standards and will stay in the shop. So compared to the big bore, you got to have your stuff just right, where the big bore is going to be much easier for you to dail in. And being a little off, won't cause you to break out the pocket book so quick. I guess they don't call it the purple piston eater for nothing. But really, I have seen some 66 to 67 mph Coffman boats with a stock cylinder, but you know what, I'm already getting that kind of performance with my Big Bore, so why even go there. Now add the correct 951 porting with the pipe and you have a total different animal. Problem? There's only a handful of people that know the correct way to do this setup. Pipe price is around $850 to $950. But the nice thing is you can have a nice used one for as little as $300. Good acceleration and speed gain, but must be setup correcty to perform. A small prop will be required, so a stock 15/20 Concord will not work on this setup. Negatives, are this setup with a small prop turning 7300 to 7400 rpms will be no faster than a big bore turning a large prop around 7150 to 7200 rpms on pump fuel.

  4. #4
    YudLuz2's Avatar
    Join Date
    Jun 2005
    Flowood MS
    951 Porting on a stock pipe boat.

    Every hear about the level one guys that are about to get some port work and are about to go out and kick some a$$. Well its not going to happen with just adding this mod to your boat without anything else. Its time to get your feelings hurt. You just got a nice port job, but guess what, It didn't do crap, no gain, maybe it is faster. Well go ahead and wish and throw your money away, because its not going to happen. Why? Well the stock cylinder on a 951 is very good from the factory, its got the sleeves matched up nicely and you already got those rave valves that help boost your low and top end performance. There are a few people that can do the porting to give you some gain, but its better to do it a different way. I will give you a example. I have a nice Mel Miller rec ported cylinder on my worked bench. Its done by one of the best in the business, work is a awesome sight to see. Cost anywhere from $400 to $800. Cost is based on how much time I have in it? Gains on a stock motor? Almost nothing. Maybe a boat lenght? Maybe a 50 rpm gain or a tad more. And you let Joe blow do yours? Thank me later, but you ain't getting nothing for your nice wad of money you just laid out. Porting is a art work, you either know it or you don't. Remember those old Yam, Kaw cylinders with the mismatched sleeves. Well it was pretty easy to get a nice gain out of those, but not a nice set of Rotax cylinders. I have ported a large number of cylinders in my past, but I can honestly say, try to copy someone or even having a cylinder that is a work of art, sometimes doesn't amount to nothing but a heart ache. Got to add a performance pipe for this mod, and then you better hope you got the right guy to port our cylinder for you.

    Step 9 Big Bore Whats involved? Install? Jetting? Why does it work?
    What does it feel like to ride one of these boats?
    Step 9 Big Bore Whats involved? Install?

    Since this will probably been a lot of info, I'm going to break this down into smaller sections.

    First you need a cylinder. Why not just keep your stock one for a spare or sell it as a complete setup. You can buy a damage cylinder these days for $35 to $100. Someone sold one on ebay for $75 today. The only thing needed was a bore job. Since the bore will be 91.89 mm, most any cylinder will work except the ones with crack sleeves. But picking up a used sleeve for $15 is no problem. So you can see where I'm coming from now, don't throw away those damage cylinders, there really worth something to some people. You will have 3 piston sizes available. 91.89,
    91.99, and 92.09 Most seizures can be easily cleaned up with the same size bore. Clearance is going to be at least 7 thous on this setup. And you can get ready to rumble very quickly. Some people like to have long break in periods. But got to tell you the truth, the choice is yours. I have bought many brand new ski's, year after year, and I never took it easy on one single unit. Always ran them wide open throttle from the time they came off the trailer, LOL. But never were they slower than any ski that was properly broken in. No difference in psi and never had a long term failure. Don't they break them in at the factory, surely they know some fool like me is going to see what his stuff is going to do in the first hour. LOL
    The stock OEM sleeves are used in the Rotax setup, the pistons are flat compared to the oem style pistons. The sleeves are pretty thin, but there seems to be no problems from taking that much material from the cylinder. A lot of the bottom section of the sleeve is cut away, exposing the transfer ports and allowing the correct fuel flow and the most import thing on a good port job is the blow down angle done to the port. These guys have mastered this from the past few years working with this motor. I like the Rotax racing pistons, there single ring and strong like the oem pistons. The setup is probably good for over 100 hours before any fresh top end job is nessary. So its a great rec. setup for the lake warrior. The piston pin uses caged bearings. I like them, no mess and I have ran them many years in other applications with no problems. You will notice in my future posting that a very small increase of fuel jetting is required for this setup. Mainly due to the fact the cylinder is flowing so much better than the OEM setup. Expect gas mileage better than a level one boat, even with a Coffman Pipe install my jetting didn't change. Even my boat still gets better mileage. Why? Look back in my later posting and you will find the answer. Proper setup. You can use two different heads. First a modifed OEM head. Its nice and it still looks completely stock. But you have the extra expensive of buying the 1050 head gasket. Which can be modifed stock one cut, or one done by Cosmetic. You can get a lot better squish radius if you cut the oem head. On the other hand, you can use a Miller head or some other aftermarket head. All you need is a set of stock 1050 49cc domes. These domes were design for the Miller Wiseco pistons, but will work fine on his setup. Thinner base gasket or having the top of your cylinder deck is required to get a nice tight squish. The tighter the better, but remember your playing with octance requirements when you go tighter. I'm running 50 thous squish clearance on my Miller head, with a psi around 145 to 150. Starter has been crapping out, I will install a new one this week, and report back. Since these domes are not cut for these semi flat top pistons you can run a lot more aggressive squish. With the modifed OEM head it's not required, since the cut is done for these pistons. I'm currectly running 70 thous squish on my modifed OEM head at somewhere around 13to5:1. So I will be lowering it with the next week for a increase in performance. A will probably be shooting for around 55 thous on this head, race motors are ran at 38 thous with this setup. So I got a lot of room to play with.
    A difference of 60 to 70 thous, is like night and day, and good for around 8 psi. Much improved acceleration. For the record, my cylinder was deck 3 different times, it's now had a total of 32 thous, taken off the top and I use a 5 hole base gasket now. I will talk more on my tweaked setup later and tell you what gains I had by trying some trick stuff. Like decked cylinder on the exhaust pipe side. Beleive it or not, its going to take the whole summer to test my new ideas and setup. I'm currently doing some now. Nice thing about using the Miller domes head, is 0 rings at 15 cents a piece from my local supplier.
    Its easy. Just like rebuilding a top end. Everything just bolts down like a stocker. Its probably going to be easier for you to install it while your motor is out of your boat. But I don't do it this way. Its a pain to get the pistons started because the sleeves are cut away where you are pushing the rings up into. The problem is they don't catch until they get a lot deeper into the bottom of the sleeve. So you might want to find a friend. Be happy there's only one piston ring to deal with. Thats all for tonight enjoy. Oh, I think the word is spreading, we got over 900 views on this article. Maybe there will be more coming from over from the dark side.

    Step 10 The good stuff.
    Reaching out for 75 mph

  5. #5
    Hello Ben, first of all, great input on the 951. I love that motor, very few can rev as quick as it does...
    I have a 2002 gtx 951 with rossier 49cc head, carbon tech reeds, hot rods crank and rods, wsm platinum piston kit, stock bore,stock pipe with rossier water jet restrictor mod, lightweight pto, novi 46 carbs, rd intake, scat 12vane set back pump w/ 16/23.5 prop on a 84mm ring. Have had best gps at 63.0 at 7170 rpm.
    I am still experimenting with jetting by plug color and rpms, and have debated on using a egt gauge untill i read your post.
    Have you used the 46 novis on your combo and if so, what sea level jetting combo should i use.
    Thanks again for the great free info post...... Rossnemo..

  6. #6
    YudLuz2's Avatar
    Join Date
    Jun 2005
    Flowood MS
    I have never used the Novi's on my setup. Tim at Novi usually
    is spot on with his jetting he recommends. I love the stock
    carb setup because the jetting works year round, never any
    issues, the Novi's are another story. If you are looking for a
    little more speed/acceleration try a 15/21 Concord in your 148mm Scat
    pump with a 84 mm nozzle. You will need to order a prop for
    a stock pump Kaw. 1200 STX-R Part number KG-CD 15/21
    to work. In my 98 GTXL with just a set of air filters, jet kit
    and Scat 12 vane setback pump it went 63.7 mph. No other
    mods. Ben

  7. #7
    Spike's Avatar
    Join Date
    Oct 2006
    YudLuz2 Lots of info there, Thanks for sharing. I have a XPDI and from what I hear there is not a lot available to improve it. It's stock and when I'm not showing it off trailering back and forth to the dealer, I use it for wave jumping in the ocean. I would like more acceleration with this one.
    Have you had any good experiance with the improving the DI models?

  8. #8
    Moderator RX951's Avatar
    Join Date
    Apr 2005
    League City, Texas
    This is excellent information !
    Definitely Thanks for Sharing

  9. #9
    Duke's Avatar
    Join Date
    Jul 2006
    Wow, that was alot of info Ben!

    Thanks for sharing that with everyone!

  10. #10
    800AMSOIL4U's Avatar
    Join Date
    Aug 2006
    Morgan Hill, CA
    Thanks for the info. I just printed it out for 2 of my friends that have the 951's. I just put up this link so people can print it out.
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