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  1. #1

    Join Date
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    opinion/advice - cylinder

    I have a 95 SL750 with a cylinder problem

    cylinder 1 (closest to the front of the boat?)
    has a hole in it. I can see the hole when I look through the spark plug hole. # 2 cylinder seems dry and #3 looks ok.

    it appears to have run quite hot at some point but I can't attest to it.

    So... opinions. Should I buy a rebuilt motor and replace the whole thing or do an engine rebuild? I can't say whether the block is cracked, but I can definately say the bore is scored on cylinder 1.

    I'm not handy enough myself to do this rebuild, so it will be outsourced.


  2. #2
    BBCaprice's Avatar
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    Uh-the hole you refer to isnt one of ex/int port holes, is it? Does it turn over? If so, do a compression check.

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    Where are you located?
    How long have you had this Polaris?

    The frontmost cylinder is known as the MAG cylinder, the rearmost is the PTO, and the middle one is the CENter.

    Is the hole right through the middle area of the piston?

    A typical cause for the piston failure you have described is fuel starvation, aka LEAN fuel-air mixture. Lean operation creates excessive temperatures inside the cylinder, which melts a hole through the piston top. This is usually caused by the carburetor(s) becomming clogged or gummed up with debris or old gasoline.

    It can also be caused by the fuel lines aging, or the fuel pump aging. Unless you have been changing the adjustments on the carbs recently, those settings should not have caused the failure.

    The normal repair process would involve repairing the engine itself, AND also correcting all the possible causes for the failure. So the carbs must be disassmbled, cleaned, and rebuilt. The fuel lines should be replaced, along with a new fuel pump.

    If only the engine itself is mechancally repaired, the new engine will fail again in short order - the fuel system and carbs must be serviced.

    If you are going to have ALL the work done by a shop, then you need to decide how much money the ski is worth to you, in running condition. The labor time needed to swap engines, plus all the other related carb and fuel line work, adds up at shop rates.

    The failure you have described is VERY common, and many of the members on here have rebuilt their engines, along with the other typically needed fixes.

    Should you decide you are willing to learn how these things are built, and repaired, and do the work yourself, you will get lots of advice and guidance here.

    You can purchase a used motor, or a rebuilt engine, or repair the one you have now. You can also have the carbs serviced, or do them yourself.

  4. #4
    axgrider73's Avatar
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    Do you have a dollar limit on how much you want to spend on repairs?

    If there is a hole in the piston then there is likely pieces of the piston in the crankcase. Therefore, a quick cylinder rebuild is unlikely.

    It's hard to say without more information, but if you are going to pay someone to repair this ski, you will probably have more in the rebuild than the ski is worth.

    If you could do a compression check and check the crank index it would give us a better idea of the extent of the damage.

    Maybe find a good used engine???

  5. #5

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    Thank you all for your quick responses.

    yes the hole is through the top of the piston, I can see it directly down the spark plug hole. I had a mobile service come by to look at it this morning and they are going to quote on both a rebuild and a replacement engine.

    He did mention that fuel lines and pump were replaced recently. someone definately had the head off the engine as there's red hi temp sealant around it and the manifold as well. probably someone went in (inexperienced) saw the problem and just put it back together.

    I'm not into the boat for very much so I can bear a bit of a hit.

    How much would a used engine cost me? Installation by the mobile service will be around $300-375 so that's fairly reasonable.

  6. #6
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
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    Do you really want to drop that amount of money to have someone else do it when you could get a friend to give you a hand on a Sat. and pull and put a replacement motor in. It's no real big deal. But the reason it burnt down is something that has to be tak'in care of before spending money on a new motor. Something is out of Wack to cause it to happen.if not found,it'll happen again.Also alot of general marine repair places may not some of the updates that are needed to prevent future problems.
    We're all here to help.

  7. #7

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    did we say we love pictures . first thing on your lists of must needs besides a good set of tools is a digital camera

  8. #8
    axgrider73's Avatar
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    Quote Originally Posted by jazgeek View Post
    Thank you all for your quick responses.

    yes the hole is through the top of the piston, I can see it directly down the spark plug hole. I had a mobile service come by to look at it this morning and they are going to quote on both a rebuild and a replacement engine.

    He did mention that fuel lines and pump were replaced recently. someone definately had the head off the engine as there's red hi temp sealant around it and the manifold as well. probably someone went in (inexperienced) saw the problem and just put it back together.

    I'm not into the boat for very much so I can bear a bit of a hit.

    How much would a used engine cost me? Installation by the mobile service will be around $300-375 so that's fairly reasonable.
    I am going to going to guess that a rebuild would cost in the neighborhood of $1000 + or - depending on if the crank is in good shape.

    Prices on used engines will vary a lot. You might try John Zigler, to see if he might have something used. his link is in my signature.

  9. #9
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by jazgeek View Post
    ...I had a mobile service come by to look at it this morning and they are going to quote on both a rebuild and a replacement engine....Installation by the mobile service will be around $300-375 so that's fairly reasonable.
    Where are you located?

  10. #10

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    Thanks for the info. I'll see if I can get picks for y'all. I'm teetering right now on whether to get a new engine or fix this one. I'm waiting for a quote back to see.

    K447, I'm in Markham. Going to the boat show? I'm going on monday night to see what's new and cool.

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