SBT says water killed the engine, need help.

[Texwing]

Thanks to SBT for living up to their no fault warranty without hassle, I have a replacement engine for my 1995 STS 750 kawasaki jet ski. After 22 gallons of gas and a meticulous job of following the break in procedure, the ski was running great and I was just starting to try wide open throttle for 5 to 10 seconds at a time. I had just put in 7 gallons of premium and added premix oil. At WOT the tach indicated just a touch over 6000 rpm (is that about right?). At about 80% throttle, the engine just disintegrated, with the mag piston letting loose, rod breaking and trashing everything it could get to. After disassembly, the pto piston looked nice and oily. The mag piston top was intact and not holed, but the pin had ripped away from the piston.

I got the replacement engine today, and the autopsy report said "water ingestion", which was not what I had expected-I was figuring on fuel flow failure at high speed and eying the fuel pump pretty hard. The ski had not been sunk, rolled, run on a hose, or anything else, so it would seem that water in the engine would have to come from one of two sources: fuel, or the cooling system.

Fuel:

Even though had just refueled, water in the gas seems unlikely since
A. it was running great
b. the pto piston looked good, and bad gas would have hit it first since the fuel pump is on that carb.

Still, it would seem smart to check. Seems like i saw some paste somewhere you could put on a stick and insert it into the gas tank to test for water, anyone know where to get that?

Cooling System:

When the engine disintegrated, the rod KOd the exhaust manifold, so that part will be replaced. What other parts, and how, should I check for cracks that could have caused this? I understand how the cooling water flows, and was very diligent on using spray copper gasket coating on the exhaust gaskets. I am unclear on how cooling water could make its way into the crankcase.

thanks fot the help, and any ideas are appreciated.

[Technical Support]

Re: SBT says water killed the engine, need help.

We may have said water damage because there had been signs of water in the engine when we inspected it, But when an engine comes back to us with that much damage it is difficult to say what happen first. Did it over heat causing a seal to fail and water enter the cylinder or did it ingest water first causing the engine to lock up, that’s the Big Question. Overheat could be from cooling system blockage or lack of fuel to the cylinder, keep in mind that a 2 stroke engine needs the correct amount of fuel in the cylinder to control the cylinder temp, without the correct amount of fuel the engine it will burn down from running too lean. Water that enters into the cylinder jackets and exhaust systems main job is to stabilize the engines temperature, but cannot on its own keep the engine from overheating. A fuel system that is not clean or set up properly will result in an over heated engine and severe damage to the engine. An over heated engine will also cause gaskets and seals to fail causing water to enter the engine. All in All when putting your engine back together don’t over look anything, inspect your cooling system and go through your carbs and fuel system, this is the best way to try to pinpoint where to problem started. When engines come back to us at SBT we don’t have the rest of the components from the failed engine to help with our failure investigation so we go by what we see.

[kpizzeck]

Re: SBT says water killed the engine, need help.

Probably busted head gasket, running at those RPM will crater an engine in a heart beat; look for gray and white when you bust it down. Water does not compress like fuel in a gaseous state.

[Texwing]

Re: SBT says water killed the engine, need help.

The cooling system was clear and putting out good water out the check fitting out the side, after it blew up I touched the head and it was not particularly hot. After talking to sbt tech support I am going to look at everything, but with particular attention to high speed fuel delivery. I would like to figure out what wot throttle rpm is on a stock 1995 sts 750, that might be a clue as well.