1998 Kawasaki 750ZXi overheated engine rebuild

[dlogvine]

Today I made a huge mistake, I allowed my daughter and her boyfriend to go alone on my jetski. Hour later they both came back without the jetski and told me that it stalled and they left it with some people about a 1/2 a mile away. So I went there to see what was the problem and saw the jetski with fried engine, the cylinder head was black instead of green and the exhaust manifold and exhaust elbow were both well smoked. In my opinion these two lovebirds got on the sand of the shore or a sandbar and got an intake full of sand since I saw sand everywhere when I started taking the engine apart.
Now, Im planning on rebuilding the top end of the motor, but since I have not worked on the jetski engines before, I would like to find some detailed description of the process. Seloc manual is very crappy with bad pictures so if anybody could lead me in the right direction, that would be greatly appreciated. Also since the cylinder head was so black, how could I check if it was warped and if it needs milling to be reassembled later. Also which parts should I replace and which parts should I check at the machine shop?
Thank you.

 

[QBhoy]

Hi

do a compression test on it and see what the numbers are. Then look up GreenHulk forum and ask those guys.

 

[dlogvine]

There was no compression, this i could tell you without even testing it. I took apart the top unit and, oh man, sand was everywhere. Exhaust manifold, exhaust elbow. It covered all the water passages and therefore there was no water cooling. Took it to the shop today, they will mike it. From the first look the owner said there should be some boring required since the ring was sitting losely when he inserted it. After I get the top done, I'll get the top rebuild kit, it runs around $250 and finish rebuilding it. Actually I was surprised how easy was disassembly of this engine, much easier than v6 or v8 Mercruisers.
Life looks much better now.
Thank you for the GreenHulk forum, definitely get on it. Asked on PWCForum, but no response.

 

[dlogvine]

Found out the cause of overheating. Looks like I should not have yelled at my daughter and her boyfriend. After rebuilding the top unit I took the ski to the lake for a test drive. The engine was running like a clockwork but after idling for a minute and checking for leaks and not finding any I made a test run around the dock. Engine started overheating even on low gas. Took it back home to inspect all the cooling hoses. When I looked at the main feeder hose supplying water from impeller to the cooling system, I discovered it slipped off the nipple but was still aligned so that made it very hard to see without a close look. So I attached and reclamped the hose. One other break I discovered was a coupling hose from expansion elbow to the waterbox was all dried out and cracked, probably leaking all the fumes into the engine compartment. So now I'm trying to find a replacement for this hose, since Kawasaki stopped producing parts for this engine. I might as well go with an automotive radiator hose.

 

[Scott06]

You know the boyfriend had to be shi$$ing his pants when the engine was roached and You hadn’t determined the Cooling hose came off

 

[dlogvine]

You know the boyfriend had to be shi$$ing his pants when the engine was roached and You hadn’t determined the Cooling hose came off

These too happy campers, left the PWC floating by the far dock about a mile away, asked somebody to watch it and returned as if nothing happened by foot. I had to go there and not willing to ask people to tow me, dragged the jet ski along the shore line. Half time swimming, half time trying not to break my foot on the slippery underwater rocks.

But now it is fixed (hopefully), I found a small leak on the expansion chamber (about 1/16") and patched it with the JB Weld, also discovered a stripped heli-coil in one of the holding bolts in the exhaust manifold, replaced it, did some minor fixes. Checked the compression- about 130-135 PSI in both cylinders. And took the jetski for a run on the lake, worked well, felt like a lot more power than before the repair.
Thank you all for help!

 

[ErvinWatson]

Found out the cause of overheating. Looks like I should not have yelled at my daughter and her boyfriend. After rebuilding the top unit I took the ski to the lake for a test drive. The engine was running like a clockwork but after idling for a minute and checking for leaks and not finding any I WalgreensListens made a test run around the dock. Engine started overheating even on low gas. Took it back home to inspect all the cooling hoses. When I looked at the main feeder hose supplying water from impeller to the cooling system, I discovered it slipped off the nipple but was still aligned so that made it very hard to see without a close look. So I attached and reclamped the hose. One other break I discovered was a coupling hose from expansion elbow to the waterbox was all dried out and cracked, probably leaking all the fumes into the engine compartment. So now I'm trying to find a replacement for this hose, since Kawasaki stopped producing parts for this engine. I might as well go with an automotive radiator hose.

Thank you for posting something like this

 

[guy48065]

Found out the cause of overheating. Looks like I should not have yelled at my daughter and her boyfriend...

(Not necessarily to the OP): They might not be 100% to blame BUT you're probably correct that they beached it and plugged up the complex cooling system with sand & silt. They also ignored the overtemp light. Your share of the blame might be in not explaining the importance of these things. LOL