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  1. #1

    Exclamation Bigger motor in a '98 slth 700

    Hi,
    I have a 1998 slth 700 with around 140 hours on it. It is my first ski and has been a lot of fun so far, but I think it is time to make it faster. From what I have read so far, upgrading to a bigger motor would be the best bang for my buck. I have got about $1,500-$2,000 to spend. If I was going to go with a bigger motor what are my options? Also, will a bigger motor "bolt right in", or am I looking at decent sized project?

    Thanks ahead of time for any and all replies!


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Welcome to the Hulk

    It may make more money sense to buy another complete PWC, and either keep the current SLTH, or sell it into the spring/summer market, when prices are highest.

    If you are willing to do an engine swap in your current SLTH, you can probably handle the work needed to bring another PWC up to good operating condition, provided the engine is in decent shape internally.

    Swapping a larger engine into the SLTH hull is certainly doable, but there is more than the engine involved;
    The ignition CDI and electrical box must be upgraded to a three cylinder version.
    The jet pump impeller must also be changed to match the added engine power.
    The three cylinder version of the exhaust manifold and some related parts must be installed.
    You will need the triple carburetors and intake manifold.
    The engine mounts in the hull may need to be relocated.

    When pricing an engine, these related parts may not all be included in the price.

    Careful shopping for a three cylinder Polaris should turn up a number of interesting options. Polaris made 900, 1050, and 1200 versions of the red three cylinder domestic engine, in 2, 3, and even 4 seater hull versions.

    Do you want to stay with the 3 seat SLT size hull?

    There are some power boost options for your existing two cylinder engine. Cost and effort wise, you would need to decide how much it is worth to you to gain the extra HP.

    Is your current engine running well?
    What is the maximum sustained RPM?

  3. #3
    Thanks for the welcome, and the fast response. I guess I could buy a new ski, but at the same time I am kind of looking forward to messing around with my slth. It ran just fine last season. I think the max rpms were around 6,300. So if I was going to try and get more power out of the 700, what would be some things that I could do? Intake, exhaust, carbs, prop, ride plate, that sort of stuff?

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    That is the age old hot rodding question;
    How fast can I go?
    How much money do you have?

    A fully tweaked two cylinder engine can deliver the same or a tad more power than a stock three cylinder '1200' engine. And that stock three cylinder engine can be tweaked to even more power, of course.

    Porting, compression, carbs would be the obvious upgrades. Tuned exhaust pipes can provide another big power boost, but are hard to come by.

    For an example of what you could trade up to, have a look at this;
    1998 Polaris SLTX - MINT COND.!!

  5. #5
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Welcome to the Hulk mtballday89.

    Where are you located?

    As a matter of fact, I was just talking to Jay from Sharps' Marine today on the phone. He and I were talking about the twin cyls, and how cheap they can be compared to the triple cyls. They tend to run 33% cheaper , and he assured me they can be made to run better than a stock triple.

    With that kind of budget, I'd be willing to bet you can make a real beefy 700 or maybe even a 777 engine for your ski. I'd suggest contacting them and see what they have to offer.

  6. #6

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    840cc Big Bore Kit with stock crank

    Quote Originally Posted by mtballday89 View Post
    Hi,
    I have a 1998 slth 700 with around 140 hours on it. It is my first ski and has been a lot of fun so far, but I think it is time to make it faster. From what I have read so far, upgrading to a bigger motor would be the best bang for my buck. I have got about $1,500-$2,000 to spend. If I was going to go with a bigger motor what are my options? Also, will a bigger motor "bolt right in", or am I looking at decent sized project?

    Thanks ahead of time for any and all replies!
    I did a lot with big Bore kits back in the day I did Big Bore kits for 700 and 1050's on a 700 using a 68mm stock stroke crank and rods I had 840cc BIG BORE KIT I do a lot of the now with Snowmobiles they are almost the same engine.
    I started with Polaris 700 Snow cylinders sleeved them to 89mm and there 2 over bores after that so you have tons of life left after the 89mm.

    1. Stock crank I would say to rebuild it to start with
    2. Cases need to be bored to take the larger sleeve.
    3. Bolts the big bore kit on

    When I did them I used the Polaris 700 snow cylinders there like a MSX 140 cylinder they have boost exhaust ports that a big help.

    1. Most used a nice set of carbs like Novi's or Black jack some like that.
    2. Randy at watcon can program a CDI for it.
    3. On Exhaust there where people running Modified stock pipes or going with a 1050 Red pipe or if you can find a set of Hurricane Twin pipes.

    I still have parts to do these and the pistons I used they still make them I just modified them so pistons are not a problem.

    cost about 1500.00 for the big bore kit and machine work but again if I where you I would do the crank also.

    let me know if your interested PM me

  7. #7
    PolarisNut's Avatar
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    Quote Originally Posted by lovehavenfun View Post
    I did a lot with big Bore kits back in the day ...
    What 89mm pistons are you using? PSI? The 700 sled cylinders (845 and 220) have port timing that is way too hot for a PWC (a snowmobile doesn't apply heavy load to the motor until its running over 4000 rpm)...it will be a turd on the holeshot, unless you decked the base of the cylinder to lower the timing...then you have to completely redo the head to accomodate for the piston coming out of the bore, now that the cylinder sits lower. You also will have to do something with the water routing, since the sled cylinders don't have water inlets at the exhaust ports. The 1050 red pipe WILL NOT work with a twin cylinder engine either.

    Long story short, if you want more power and you have a 700 twin (especially in a big 3 seater)...buy a 1050 or 1200 triple ...you'll spend a small fortune getting it to go fast. The tripple will always have more torque, and that's important in a PWC. I used to ride a '96 SL700...then I took a ride on an SL900 triple...There was no comparison. I kinda see it like buying a V6 Camaro and trying to make it go fast...sure, you can get it into the high 12's on nitrous, but a stock LS1 V8 with boltons will still beat it, and it will be more reliable and fun to boot. Just my .02...I've wasted a LOT of money on performance mods on different toys over the years...My rule is to usually start with the biggest motor you can (within reason).

  8. #8

    Smile Anything you can do to a 700 you can do to a 1200

    The bigger engine less mods is the most reliable way to go,also cheapest in long run,if you want to work on a ski ,buy a 1200 in the model of your choice,with a blown top end or piston rebuild it with parts of your choice,My customer just bought a like new carbed 1200 with bad front cylinder for 300.00 from a dealer,its missing carbs,for 2,000 he will have new crank(rebuilt/welded,wiseco pistons(lower weight faster revving)like using lightened flywheel but better and all new orings and gaskets.so for around 2300.00 total he will have a like new ski,then you could sell your present ski and recoup the money or have 2 one for your friends to ride.JMHO>Marvin

  9. #9
    Yeah you guys are probably right. Maybe I will just clean it up, sell it, and buy a bigger ski. So what would be a good low priced 1200 to look for?

  10. #10
    bowsniper's Avatar
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    I just bought a 2000 slx 1200 with the 3-cylinder 1200cc motor in it for 500.00 Plus the cost of going to get it. 240.00. fires right up, 130 across the board and looks great. I would think you could find a deal like this too.

    look at my avatar. thats it!.

    A 1200cc is the way to go for reliable big power. it just doesnt mess around. ya hit it, it flys!.lol

    Theres tons of mods you can put on the ski too. plates,grates,impellors,wedges,carbs,triples pipes if you can find them,other goodies too.

    Theres always the PRO785 or a 1200PRO if you want to go super quick and fast. Theres a guy on here who changed a 750 motor from a 3-seater slt and installed a 785PRO motor WITH the triples pipes on the ski!. Does 63-65 MPH!.

    But even still, the SLX stock will go 63 too. Just doesn't get there as quick. Just a fun nible ski Iv'e heard. I haven't riden it yet..

    If you feel like you have to go FAST! and be the quickest out there...get a PRO! And you can mod these badboys out too! Even Faster,Ever Quicker! (got 1 of those too! )


    I hear theres a ski called a X-45,, but Iv'e never heard much about that particular ski..


    If your looking for a NEWER looking ski, then a Virage,X-45,MSX,Genesis are more what your looking for and they have domestic red 3-cylinders in them also but have fuel injection systems in them or carbs..I don't know much about these particular skis..

    That ski k-477 was talking about is an awesome ski. wow.. looks brand new and runs like it. Thats a good ski to buy!

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