I have a 1990 waverunner 650. I took it out a couple weeks ago and it started up and ran for about 15 minutes then bogged down and eventually died. I've tried every fix possible. Ive checked compression, spark, carb rebuild, kill switch, fuel filter, fuel pump, changed plugs, fuel selector valve. I cant seem to get this to start and actually stay running more than a minute or 2 in or out of water. Any suggestion? One more thing, the shaft seal on the back of the engine seems to partially blow out when it does start. May this be a problem if it doesnt have a good seal? Ive heard that if the crankcase has a leak the fuel may not reach the cylinder like it should. please help