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  1. #1

    1996 SL780 Got wet- now Bogs and Dies at WOT

    I went to look at a 1996 SL780 on Saturday to try it before buying. Guy says he is a mechanic and winterized it every year. Took it out and it ran fine for about 5 minutes but was very difficult to turn. Then the red light started flashing on the MFD and it read "HOT," and went into limp mode. I immediately headed back in. It ran until I got in. Barely got to the dock, though, because it started sinking. Get it up on the trailer and it is half full of water. I didn't notice quite how high it was, but it could have gotten into the carbs. I was just so anxious to get the water out I pulled the plug as fast as I could. Turns out a cooling intake hose had become disconnected, probably from when the guy winterized it and didn't tighten it back down.

    Tightened the hose back up, got it drained, took it back out because it fired up fine, the plugs looked fine. It idled and ran fine at low speed getting out of the no wake zone. Out on the water, at WOT it would bog and run at around 4000 RPMS. If I let off the throttle briefly and then got back on it at WOT, it would run flat out again, but only for about 10 seconds, and then it would suddenly cut out and die. It would start right back up without a problem. Pulling the choke when bogging would cause it to die. Trying any manuevers like hard lefts or rights at WOT would at first work fine, but after about 5 seconds, it would cut out, die and then start right back up again. I went through this process (bog,let off throttle, get back on it at WOT, it runs for about 10 seconds, then dies, starts right back up, etc.) for about 15 minutes and then came back in to look at the plugs.

    The plugs were black, so I don't think it was running lean. Looked at the fuel/water seperator, it was full of water so I drained it. I noticed that the gasket between the fuel tank and the cap with the distribution lines coming out of it was worn and missing a about a quarter-inch piece. Tried to eyeball the pistons through the plug hole and the part I could see looked normal.

    I have not taken it back out, because I am worried about blowing a piston. Any advice would be appreciated. Could the water in the fuel/water seperator have been the cause of my symptoms, or is it more likely there is water in the carbs? If so, do I have to pull the carbs to get it out? Any thoughts?


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

    Is there water in the fuel tank?
    Sometimes the cap gasket or tank filler neck can crack and allow water in.

    When you ride with water in the bottom of the tank, the bouncing around as you ride can move the water towards, or away from, the fuel pick-up inside the tank.

    Click here for the Polaris Service Manual, and other useful info.

    I presume you have checked compression, and it was good. Did you check it again after the flooding?

    I would expect any water in the carbs would get drawn out as the engine runs, but I could be wrong.

    Since the engine has now been overheated, it is possible that a gasket or something is leaking water into the engine as it runs. Hard to say...

    I would start by checking the fuel tank for water, and checking the gas filler for water leaks. There should be zero water in the fuel tank, and the fuel-water separator should only have gas in it under normal conditions.

    Of course, the fuel tank seals must all be in good condition, as fuel fumes inside the hull can be deadly.

    Another area to check is the electrical system. There should be zero moisture inside the electrical box, and no corrosion. All connections should be clean and tight.

    Often the spark plug wires need to be trimmed 1/4" and re-attached to the spark plug caps, to ensure a solid connection.

  3. #3
    Thanks for the reply. Is there a way to check for water in the tank without draining it? If not, I assume I have to rig a way to siphon the gas out and then look at what comes out to see if there is water in it?

  4. #4
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Welcome to the Hulk cdiddy.

    Lots to get into with that one.

    First, you need to find where the water is getting into the fuel.

    Next you should get into the carbs to see if any water is inside them. Also give them a thorough cleaning while in them. (water can become trapped inside)

    Any time a 2 stroke engine dies at WOT, you've got problems.

    You're "A" overheating and seizing the pistons

    Or "B" starving the engine of fuel.

    Both of which are terrible for the pistons.

    Perform a compression test and get a good look at the piston domes and cyl walls.

    Good luck

  5. #5
    Wouldn't the plugs be white if the engine was running lean? Wouldn't the MFD tell me the engine was hot and throw it into limp mode if I was running hot?

    I ran it again today for about 15 minutes after cleaning the fuel/water seperator, and there was no change. It would only rev to about 6000. The MFD said I only got up to around 30 MPH. Checked the plugs again and they were black/dark brown.

  6. #6
    I wanted to post the resolution to this in case anyone else is having similar issues.

    I took it in to my dealer and he inspected the carbs and said they looked fine, he adjusted the jets and also rebuilt the fuel pump, saying there was grit in it. I took it back out and there was no change-still doing the same thing.

    After poking around on this site a little more, I realized a couple of things: 1) I was basically getting the rev limiter kicking in, as I couldn't rev past 4200 RPMS unless I backed off the throttle and the went WOT, at which point it would run for five seconds and then die; 2) there was no warning light, or error on the MFD which would indicate the reason for the rev limiter kicking in.

    I then saw that someone on this site had the same issue, rev limiter with no MFD error, and it turned out to be the LR-54 module. This got me thinking that the problem may be in the electrical box. Since this all started when the engine compartment got flooded, I knew there might be water in the box, but I had put off opening that box up figuring the dealer would have done it if that was a likely cause of my problem. Opened it up and yep, sure enough, there was about 1-2 cups of water in there. Dried it all out, took it out to the lake, and bam, runs great, no problems.

    Thanks to those of you who helped out on this, and thanks to the guy who posted his resolution regarding the LR-54 module, it got me on the right track.

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by cdiddy View Post
    ...figuring the dealer would have done it if that was a likely cause of my problem...
    There is a good lesson in there - Don't count on the dealer doing everything that should be done.

    Even the better techs are often under time pressure to get a lot of other machines fixed, and may not be able to take the time to investigate every possible item.

    This is true for other brands, not just Polaris.

    You are often far better to investigate the problem yourself. Be thorough, take the time to learn how it is put together, and how things are supposed to be working.

    Not only will you be able to handle the vast majority of things that need attention, but you will also have a more reliable machine, because you will know the machine.

  8. #8
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Thanks for the results follow up.

  9. #9
    Ctek's Avatar
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    Thanks for the update. Good thing you had the common sense to check that before it got worse.

    Did you have to replace the board or fuses or just dry it out?

  10. #10

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    Quote Originally Posted by K447 View Post
    There is a good lesson in there - Don't count on the dealer doing everything that should be done.

    Even the better techs are often under time pressure to get a lot of other machines fixed, and may not be able to take the time to investigate every possible item.

    This is true for other brands, not just Polaris.

    You are often far better to investigate the problem yourself. Be thorough, take the time to learn how it is put together, and how things are supposed to be working.

    Not only will you be able to handle the vast majority of things that need attention, but you will also have a more reliable machine, because you will know the machine.
    It is very difficult being a mechanic at a dealer and MANY times watercraft problems can be a mulitiple visit ordeal.

    Main problems I run into are mainly not being able to go ride the thing like i would like to, and the customer can't ever explain worth a $hit what was going on.

    1. Most times watercraft have more than ONE problem.
    2. Customers, and even different mechanics describe things differently amongst one another. (nothing ever makes sense)
    3. No customer ever wants the entire craft to be completely checked over to verify everything is ok, as this mainly isn't feasible to them.


    Anything such as......."it won't start" "has no power" or "runs slow," or any others that are consistant problems are generally easy to diagnose and fix.

    The difficult ones are changes in performance or dying after riding, they are also the ones that make you look like an idiot if you don't happen to stumble across it right away!!

    Watercraft can be the most annoying toys to work with, but can also be very rewarding as their are very few good watercraft mechanics compared to bike/quads techs etc.. This is the main problem with having watercraft fixed at dealerships. You have to find a good dealership with a mechanic that enjoy's working on them.



    I also advise just taking the time with your own projects and learning your machine. They are really fairly simple machines, and all the knowledge and experience between everyone online helps make it all possible.

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