787 RFI 4th engine

[Bassfrad]

I have a 1999 GSX 787 RFI. last summer (2024) I bought the ski and it ran great. Few trips out no problem. About 20hrs on machine with no issues. Then ski started fouling plugs. Ended up damaging starter so I winterized it and waited till spring. Got it in shop and engine would not turn over. I had forgotten about the starter issue. I pulled plugs and hit starter and it nearly blew my eyes out with oil. A lot of oil. After crying a little over my eyes got them cleaned up so I could see. Pumped all the oil out and got it running. Put it in water and smoked like crazy. Fouled plugs pretty quick. After research I figured rotary seals were shot. I pulled engine and installed an SBT engine. (Don’t start, I know). Ran engine in water on trailer for a hr or so. Seemed fine. Took it out and everything was great. Checked plugs every 30 minutes. Looked perfect. After about 2-3 hrs out of no where engine died. Started back up and knocking. Pulled engine. Front rod bearing gone. Both pistons and cylinders looked perfect. I did run pump on drill on install. Installed another engine. Run oil pump on drill. All good. 2nd trip out same thing. 2 hrs all is good then died. No sound beforehand. Checking every 30. Plugs good. Water out of air bleed in rear and all. Installed 3rd engine. Put pump in vise and tested output volume and pressures. Seem good. Bought another pump to test against and both are the same. Tested with hoses connected to intake ports. All seems fine. Pulled and tied cable wide open. Put it on water and drive it only around 1/3rd to 1/2 throttle with an occasional WOT for 3 seconds. It will smoke some but doesn’t seem as much as I would expect. It has all new hoses and filter. After 2 hrs I checked it again. Seems fine but engine seems hotter than I expected. Any idea what my problem can be. I worried that it’s going to do the same thing. What can cause a rod bearing failure but leave the piston like new?

 

[mikidymac]

Junk SBT parts, that is what.
If it was an oil issue it would seize the pistons before anything else.

 

[etemplet]

You should be able to put your hand on every part of the engine and exhaust manifold while the engine is running. You can buy a laser thermometer cheap to determine hot spots if there are any. I'd suspect you have a cooling issue but you have a temp sensor that should be setting off the temp alarm. Very strange failures to be sure. How is your jet pump?

I'd contact SBT for sure. They should be able to help if it is their engines failing. I'm not a SBT fan but they have a lot of engines out there running great.