1988 Kawasaki water getting into engine

[shadow]

This spring my son bought a 1988 Kawasaki 550 standup jet ski. It has a rebuilt motor in it done by a mechanic from a local dealer (after hours). It will start fine out of the water; I have rebuilt the carb, checking the popoff psi and installed clear fuel lines so we could see if it is getting fuel.
Once in the water is very hard to start and the plugs foul out constantly (40:1 mixture) it appears to be getting water in the combustion camber. Could this be coming in through the exhaust? Compression is good approx. 135# each. It has a modified exhaust (factory tube). Thanks

[Bryan Glynn]

The exhaust is not a likely source. It's most likely a blown head gasket, or cracked water jackets. I would first pop the head and inspect the gasket for blow-by. If you see signs, obviously replace it and try again. If you don't, you may need to pull the engine out and have it fully pressure-tested to find the leak.

[shadow]

Wouldn’t this show up in the compression test? If not how do I do the water jacket PSI test? Is this something that I can do?
Let me explain the trouble further. It will run on the water but if he jumps or bucks waves it will start to die out. He will run it (appears to be running on one cylinder) until it starts to run good again. Yesterday we hooked it up to the garden hose and he opened the water wide open. The engine had lots of water getting into it. So we cut back the water and did not turn it on until the engine was running, then it was fine. Is this normal? Thanks again Dave

[RadioDave]

If you are blasting the water into it on a garden hose, you can fill the motor with water. You only want to use enough pressure from the hose to get a small stream from the bypass outlet. You should turn the water on after starting the motor and turn it off just before you stop the motor.

If it is dying when you hit waves, you may have water in the seperator that is getting into the fuel supply when you shake up the ski.

There are many things that can cause good operation on the trailer and bogging in the water. I have an '87 JS550 that I've spent much time wrenching on over the years along with those of several friends of mine. It has been my experience that most times this symptom is caused by fuel-related problems if the motor is truly, mechanically healthy. If you have a Super-Trap or other ring-type muffler it may be clogged, creating excessive back-pressure. If you do have one, replace it with a water box.

One thing you MUST be careful of running this ski out of the water... With improper mixture settings, the motor can run away winding up to massive RPMs as it will run like a diesel using cylinder heat and compression for ignition and you won't be able to stop it with the stop button. If you have a primer, pump the hell out of it if this occurs to flood the motor. If not, have some gas handy to dump down the carb. This precaution is EXTREMELY important and you must be prepared for this when trying to get the motor dialed-in.

This is great ski to tweak on and have fun with!

Good luck!