1991 SP runaway condition (yellow engine)

[arizonabuild]

Hello, thanks for the add. Been searching for answers for a while and decided to finally sign up. Look forward to being part of the community.

Currently have 3 Yamaha waverunners and just picked up a 1991Seadoo SP with the yellow 587(sounds like you guys probably get a lot of these first posts!). It has been sitting since 2007. Removed the mikuni carb and re built it with an oem kit. Replaced all the gas lines and filter. The carb now draws fuel but goes into full throttle "runaway" mode when started. Took a working carb off one of the Yamaha 500's(same carb), used a brand new gasket, and it does the same thing so I don't believe it is a carb issue. Sprayed with carb cleaner all around the engine and could not find a leak. I'm guessing it is the crankseals but before i pull the engine was wondering if there is anything else I should look at or test first? Could leaking oil hoses be causing this? Compression appears a little low at 120 in both cylinders, maybe something in that area?

Just looking to get it running and have some fun. I'm fine with some expense and enjoy this type of work, just know very little about seadoo rotax engines.

Thanks! AZBuild.

 

[POPPS]

Could be an air leak?,,,did the carb base gasket fall into the hull?,,,is the throttle butterfly closed?,,,

 

[arizonabuild]

Brand new gasket is in place. Butterfly is closed like it should be at idle. It starts and immediately goes very high rpm until i pull the fuel line and close the choke. Could this possibly be a computer issue? I'm getting ready to pull the engine and put it on the bench but if its something im possibly missing that would be easier!

I was thinking sitting in the AZ heat for 14 years probably ruined the crank seals but am open to any and all alternatives/suggestions.

Thanks for the reply.

 

[POPPS]

It could be a leaky crank seal,,,it would not be the computer,