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Sea-Doo 787 GTX 1996

Travisgg

Active Member
Good day everyone. My machines running awesome I've always wondered about the compression though. It's always been 160 to 170 PSI both cylinders with multiple gauges. I don't know the history I'm assuming it's a stock motor. Just trying to figure out if I should be running premium fuel. Maybe that means the head's been cut a little bit or something? Let me know your thoughts! @mikidymac
 
This is of interest to me. My 787 has similar compression and the head does not look factory
 
This is of interest to me. My 787 has similar compression and the head does not look factory
I'm sure someone will respond. Mine does look factory though.... But sometimes you don't really know if someone shaved a little off... probably can't tell by eyeballing it, would have to measure.
 
Not stock compression. Yes, at 160psi you should always be running 91+ octane.
As usual you are the man. Just out of curiosity what would be some of the destruction long-term if you were using the wrong octane fuel on a high compression engine? Do pistons swell a bit and stick etc
 
Not stock compression. Yes, at 160psi you should always be running 91+ octane.
On a side note just rolled it and filled it with water the crank and everything. Water shooting out spark plug holes. What's the best way to get the engine free of water as it won't start right now I think there's too much water in there.
 
On a side note just rolled it and filled it with water the crank and everything. Water shooting out spark plug holes. What's the best way to get the engine free of water as it won't start right now I think there's too much water in there.
Wow, those are hard to roll
 
I've got the same situation with my 97 gtx, compression of 170-175. Head is not changed as far as I know. Checked with my matco gauge.

I've had issues with the battery not able to turn the engine over at times when hot after shutting down for a short bit on the lake. Two different, new, batteries. Same result. I've had to literally loosen up a spark plug on the lake to let some compression release, then it turns over fine and starts up. Tighten the plug, off i go. Dumb.

Reason i don't think it's modded, is I'm only getting 6,650 rpm's, about 52 mph indicated. If anything, i'm down RPM's.
 
Really!!? What does that do? Push the water out of the system a little quicker I assume...
Creates a vacuum in the crankcase to pull he water up into the combustion chamber and out. Remember on a 2-stroke the crankcase fills with the air and fuel mixture before going into the combustion chamber or water in your case.
 
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