HELP - 97 GTX intermittent rpm's

[CaymanCraft]

Just finished breaking in an SBT 787 engine in my 97 GTX. 10 hours of up to about 4500 rpm so far. Time to really try it out. While holding it at WOT I will get to about 30mph but no higher then all of a sudden the rpm's will increase and it will go 50mph and then suddenly slow back down. There doesn't appear to be a pattern to this as the time when it will do it is varied and so is the time it will stay at high rpm. It's like all of a sudden someone throws a switch and then I get higher rpm's. It doesn't sound like it is missing as it revs clean and the plugs look good. One thing I've noticed is that if it hits a wave it triggers the jump up to or down from the higher rpm range. I've checked for loose wires and connections but don't see anything obvious. Anybody got any more ideas?

[Technical Support]

Re: HELP - 97 GTX intermittent rpm's

Sounds like fuel starvation possibly. What caused the original engine failure and what repairs were made?

[Bill O'Neal1]

Re: HELP - 97 GTX intermittent rpm's

Take a close look at the water regulator on the muffler. You are describing a problem that is consistant with a faulty water regulator not delivering the water correctly to the exhaust system.

Other factors could be that the carbs are not functioning correctly, maybe running too rich?

Make sure the rave valves are in good condition too.

[CaymanCraft]

Re: HELP - 97 GTX intermittent rpm's

Thanks guys I will check those things out.

I bought the craft used and not running. Motor was in a box. Looked like it either ran hot or leaned out, maybe both. Cylinder walls had a lot of drag marks.

I put new carbs on it and bought an SBT 787 engine and put it in.
It did have a faulty water regulator but I put a new one on it during break in. Of course I didn't have this problem then 'cause I really didn't go very high in the RPM range.

I just cleaned the rave valves before putting them in so it could be them. There're still stock ones.

Also...After about 5 mins of moderate riding I see L Temp=89 and E Temp=102. What are those referring to and what is the recommended operating range?

[Bill O'Neal1]

Re: HELP - 97 GTX intermittent rpm's

89 = lake water tempature, 102 degrees = outside air tempature. There is no engine water temp guage on a Sea Doo. There is a water tempature sensor that sounds an overheat buzzer at 206 degrees. Normal operating tempature of the engine is around 190 degrees F.

[CaymanCraft]

Re: HELP - 97 GTX intermittent rpm's

Thanks Bill...that makes sense.