FAdileh

Recently I installed a new rebuilt Rotax 800 engine from SBT in my 1997 Seadoo Challenger. The break-in went smooth and I was able to burn about 12 gallons of premixed fuel. I still have my oil injector so the motor was running rich.

After the boat consumed almost all the pre-mixed fuel, I filled it with 10 gallons of 87 unleaded fuel. The fuel that was in the engine at break-in was 93. When I took it back in the water, the boat ran normal for about 2 minutes at 85% throttle never holding the throttle for longer than 30 seconds. Based on the information form SBT, holding the throttle doesn't matter at this point since the break-in process was complete and about 2 hours of riding around was accomplished. The engine stalled. It runs fine for 1 minute at high throttle (never higher than 90%) then shuts down. At startup after stalling, the engine idles low at around 1,200 RPM in the water then slowly climbs up to the normal 1,500 RPM. If you keep it at around 40% throttle then it runs okay. Any higher it stalls. Replaced the spark plugs and that didn't help.

I checked the following and they all functioned okay:
1. Oil injector. Introduced an air pocket on the output of the injector and monitored the flow.
2. Electrical plug to the stator housing was tight and in place.
3. Ignition wires were fine but I still cut the wires and tightened them.
4. The fuel valve was open fine. To make sure it is working okay, I ran the engine and shut off the valve and the engine stopped.

What could be the cause for the stalling? The carburetors and jet pump were rebuilt a week before I put in the new engine. The starter, stator and flywheel are all new. A friend of mine that works on these boats says that it could be the magnetic ignition/key combination or the throttle kill switch. I explained that the boat idles perfect and runs good except when you go at higher throttle. He said that it could be because of how rough the water is which at the time was smooth. Could this be possible and how can I check to confirm? What are things that could cause it to do this?