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  1. #1

    Is This Good Or Bad?

    Looking at possibly purchasing a 94 750sl engine for $400-450. The compression stated is 115-120psi across the board. Is that good or bad compression? Any thoughts or opinions?


  2. #2
    I'm guessing no one knows... LOL I'm thinking it's not great. But would like to know if I should consider it or not. The manual states between 120 and 150psi. So might be iffy.

  3. #3

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    compression is not bad but the price is alittle high for a 750 engine

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  5. #4
    Quote Originally Posted by 785 lugs View Post
    compression is not bad but the price is alittle high for a 750 engine
    I appreciate your input. Where can I find a working engine cheaper? SBT has them including shipping + core exchange for $1200. This is the cheapest working engine I've found so far. Especially with no core exchange. So, I get to keep my original for parts. If you have some ideas on what a fair price for a running 750 would be please help. I really appreciate any help. I'm looking at a bore, new larger piston, rings, clips, wrist pin & wrist bearing on my bad engine cylinder. If that sounds like a better way to go, please advise. I'm just not sure how to proceed. I agree that it's possible this $450 engine could still have problems. So, maybe it's better to just do the bore and piston on mine and save some cash. But, its gonna be around $200+ to fix that cylinder after the bore and all the parts. Whatcha think?

  6. #5
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    If everything else is ok, thats would be a good plan. Really check out that crank to make sure its good before throwing money at it though. Have you found what caused the original failure?

  7. #6
    Quote Originally Posted by BryanP View Post
    If everything else is ok, thats would be a good plan. Really check out that crank to make sure its good before throwing money at it though. Have you found what caused the original failure?
    All I know is the MAG cylinder has 2 minor grooves and the rod and piston were not attached to the crank I'm guessing a lean condition(had original fuel pump) threw the rod and cylinder unless someone else has an opinion on what happened. I found another crank shaft that is in good shape. Just need the cylinder bored and piston installed and install Mikuni 3 way fuel valve and it's good to go. Hopefully!?! Won't know for sure till I get it put back together and test compression. That's why I'm considering the running engine I found. Comments welcome.

  8. #7
    will a 96 SLT 780 fit?

  9. #8
    Do you have the ability to hear the running engine? If the bottom end sounds good, I'd go for that one. Especially with an engine out of the hull, it is easy to hone the cylinders and install a set of rings. That should bring your compression back up. If it turns out to be not what you want, you can still recoup most, if not all, of your money by parting the engine out. $400 is a pretty decent price for it.

  10. #9
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
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    A 780 will bolt right in, The carb jetting would be different from the 750. Price depends on the area alot of times. If you can get a good crank at a decent price, I think I would consider the hone & rering,or rebore. Then you have a fresh upper half. Just depends,time vs money. if you want to get on the water, drop a used one in and run, rering later. But for that type of money,I would want to hear it run first.

  11. #10
    I agree the 780 will fit. My auto mechanic has a buddy that can hone the cylinder and get me a piston cheap. He said the cylinders not that bad and I could probably get away with new ring alone. So, looks like hone and piston with new rings and I'm good to go. I went ahead and purchased the rebuilt engine for $400. Looking for a backup engine, running or for parts anyways. Didn't get the hear it run so I know I'm taking a risk. But, hey, I'm taking a risk thinking I can keep this thing running! LOL

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