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  1. #1

    HELP-bought 750SL 1994

    I was lookig for parts for my 94 750 SL blown engine (See thread )
    and ran across a complete ski near by. It needed a pump (which I had just rebuilt on mine before the motor blew!) It has been sitting inside a garage (with busted pump) and hasn't been turned over since 2000! The bearings on the pump shaft are welded together.

    I removed the spark plugs and sprayed fogger into the spark plug holes. I then used the driveshaft to turn the motor over by hand. Everything seems smooth and I could feel the compression. I also sprayed the fogger into the carbs while using the throttle to open and close them.
    I once had a carbon locked RX7 rotary motor and the guys on the RX7 forum suggested pouring Marvel Mystery Oil into the carbs and letting the motor soak. Since my Ski was NOT locked, BUT had sat for 8 years, I thought some MMO wouldn't be a bad idea. After all, it unlocked my Rx7 motor and I put lots of miles on that same engine that others said was no good!
    I poured the MMO into the spark plug holes until it was overflowing. I put the plugs back in so nothing would get in. It sat overnight and I took the plugs out this morning. I put a towel over the spark plug holes, and then turned the motor over by hand to work in the MMO. I cleaned up the excess oil that ran out of the holes and then I hooked up a battery. I was amazed that the display worked! It shows 39 hours! <-- wonder how accurate that is? The guy said he was the original owner and got it in 1994.
    I left the spark plugs OUT and used the battery to turn the motor over several times. (getting out the extra fogger and MMO) It sounds good. I put the compression tester on and have 110 on the rear, 105 on the middle, and 105 on the front cylinder.
    I am ready to slap my pump on this ski and GO! This ski looks so nice and clean that I don't want to take it apart! BUT I DID NOT FOLLOW THE UPGRADE SUGGESTIONS AND BLEW UP MY LAST SKI. Everything seemed fine when I bought it as well, but it only took a 4 rides to burn up the rear piston and RUIN the rest of the motor.

    1. Which forum member sells the 3 outlet fuel pump WITH the correct fuel
    lines and instructions??
    2. Can I check the oil sending unit/ pump?? Or should I just get the block
    off plate and run premix?
    3. Can I check the carbs while they are on the ski? Or should I just
    remove them and get them rebuilt? Who rebuilds them and how much?
    4. Should I run a quart of SBT break in oil, since it has sat since 2000?? I
    thought about adding some MMO to the gas tank to help with


    ( We need 1 thread/checklist for the 750 SL. There are so many
    different posts to read)

    This ski looks okay ( See pics ) and, WITH YOUR HELP, I will prevent it from blowing up! I'll be patient this time and make sure I follow all the instructions before I take it on the water. It is so tempting to slap on the pump and go!, but I learned the hard way last time.

    Thanks for your time and input.
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  2. #2

    Checked the fuel pickup lines

    The fuel lines inside the jetski look like they are in good condition. I checked the pickup lines and one is pretty bad. The gas tank is empty, other than a few clumps of sludge in the bottom of the tank. I'll have to get the tank out and clean it. Any suggestions on what to use for a cleaner? Check the pics of the fuel pickup lines. The other fuel hoses looked so good I almost didn't check the pick up line.
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  3. #3
    1. Change all the fuel lines. You are going to a triple pump so this shouldn't be all that much extra work.

    2. In a perfect world I would eliminate the injection, but it's not a job I would do with the motor in the boat. When I removed the injection on mine the bed plate was massively in the way and was a real pain to work around. My ski is a 93 though, so maybe yours would be easier. If it were me I would drain all the old fuel and then premix 3-4 fresh gallons of 50:1, then I would mark the oil level in the oil tank and check the level after a hour or so to make sure the pump was pumping.

    3. If the ski has been sitting that long I would pull the carbs and clean them. They are not hard to clean. Who knows how gummed up they ate from sitting. Sure would suck to burn it down over a dirty carb.

    4. Just about any snowmobile place will stock a 3 outlet fuel pump. Figure 30 bucks or so for one. The instructions can be found in the tech section.

  4. #4

    That compression seems pretty low. Perhaps it'll jump back up once you've run the machine but I would make sure to keep an eye on that. Pre-emptive top end will be cheaper than rebuilding the whole thing if somethin goes wrong.

  5. #5

    New compression reading

    I poured a little MMO into the spark plug holes and turned the motor over to work it in. I then took out all 3 plugs and put the compression tester on the front cylinder. I had the choke and throttle wide open and turned over the motor. I got a better reading this time:

    Front cylinder reads 130PSI
    Middle cylinder reads 121-122PSI
    Rear cylinder reads 123-124PSI

    The digital read out (MFD I think) has a red light at top which flashed a few times while I was doing the compression test. I'll search around and see what the blinking red light is for. Any clues??

  6. #6
    Moderator beerdart's Avatar
    Join Date
    Aug 2006
    The light blinks for low fuel, low oil or overheat. If you had to put MMO in the cylinders to free it up you are on borrowed time with that motor.

  7. #7
    The motor was NOT locked when I got it. It just sat in the guys garage since 2000. I fogged the spark plug holes and down the carb since it had sat for so long. I figured adding a little MMO into the spark plug holes would help lube things up as well.

  8. #8

    Removed Carbs

    I took the carbs off of my ski with the broken crank/case/piston. I thought it would be better to get these carbs rebuilt, and then put them on the good ski. That way my good motor isn't exposed to the florida air while the carbs are being rebuilt.

    Check pictures of the carbs. Did those fuel lines have the "T" in them from the factory? I'll be ordering my triple outlet fuel pump this week.
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  9. #9
    Moderator beerdart's Avatar
    Join Date
    Aug 2006
    Adding the Tee was a service bulletin to help the problem. But it did not correct the problem.

  10. #10

    1994 Polaris SL750 compression

    Does anyone know what the "normal" compression is supposed to be?

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