a couple problems ive searched forum

[upongame]

I own a 98 speedster twin 787s
My right motor seems to have no traction past half throttle, 0 to half throttle smooth half to full rpms jumps to max with feels like jumpy n doesnt bite then bites on off n rpm wont stay constent
Is it the rave system

It also accelerates when on garden hose and in trailer with no throttle given jus in forward but in neutral rpms r fine at 3k
My whole propultion systems where rebuilt recently I was told..,.
Any ideas?

 

[LouDoo]

Your problem sounds like cavitation, check the wear ring(s) the clearance between the wear ring and impeller should be no more than .025" or about the thickness of a dime. If that looks O.K. it's most likely the carbon seal.

As long as your boat idles O.K. in the water I wouldn't worry about a high idle on the trailer. Unless it runs away then you've probably got an air leak in the fuel system.

Lou

 

[upongame]

Your problem sounds like cavitation, check the wear ring(s) the clearance between the wear ring and impeller should be no more than .025" or about the thickness of a dime. If that looks O.K. it's most likely the carbon seal.

As long as your boat idles O.K. in the water I wouldn't worry about a high idle on the trailer. Unless it runs away then you've probably got an air leak in the fuel system.
Lou

Caviation?
Why would you assume air leak in fuel if its jumping the rpms and not bogging?
Carbon seal?

Just trying to understand how these things work...

 

[howie099]

A racing engine without touching anything is a common sign of an airleak that is what Lou is trying to explain to you. Cavitaion is mostly caused from worn out wear ring, damaged impeller, weak carbon seal boot, worn out carbon seal, or the enigne moving (bad motor mounts). The pump issues are the easiest to check. The boot you can try to pull it back and see how hard it is. It should be hard to pull it back if the boot is good. The carbon seal you can put waterproof grease on it but it will wearout faster but it will tell you if thats the cause.

Most people in hte carbon seal is bas they repalce both the boot and the seal with OEM ones. They are stronger and last longer. I would guess just by the age of the boat the carbon seals never been replaced. Also running your boat out of water without cooling the carbon seal will burn them up faster also just an FYI if you run it a lot on the hose.