95 Speedster cavitation

[PostDigger]

I recently bought a Speedster with twin rotax engines. Both have been rebuilt. I rebuilt both jet pumps with new parts and also the carbeurators on port side. With all of that, the starboard pump is cavitating badly at almost any rpm. The splines looked ok on pump end and the carbon seal does not appear to be leaking.
Can anyone give a bit of advice for this? I don't mind getting new parts, but would like to solve problem as well as simply change out components.

 

[Waterluvr]

Someone's made some changes if that has carbon seals, the boat originally came with the carrier bearing style seal and smooth shafts that didn't have an o-ring/clip groove to tension the carrier ring against the carbon seal.

Have a look at that starboard side driveshaft and see if maybe it's got two grooves in it for the o-ring/retainer clip whichever you're using there may be another groove that will add tension and seal better.

 

[Coastiejoe]

It can only come from few places. Bad splines, bent impeller or debris stuck in it, worn wear ring or the shaft seal. If you can isolate out things, you will narrow it down.

Also, a bent drive shaft will do it. We had a member go through EVERYTHING twice, took it apart a third time and still could not find the issue. Out of frustration he kicked his driveshaft while it was on his garage floor. When it rolled away it wobbled... Replaced it and problem was solved. The fact that someone has changed to the Carbon Seal style means it has been apart. You may have to pull the shaft to check it. Or, put a piece of chalk near it and crank the engine, see if it marks it in some of but not all of the shaft. Move it closer and further away based on what you see.

 

[PostDigger]

Thanks guys. I will investigate further.
I may have mis spoke regarding the seal. I will verify it when I get to the boat today.
My shoe looks like someone had been attempting to add sealant to the perimeter.
Is it really as difficult as I have read to correctly replace the seal for that?
Is "the right stuff" the best to seal around that as well?
I have a lot of questions. I don't want to do a poor job repairing this boat. I want it right so it lasts.
Really appreciate input from you that are experienced with this stuff.

 

[Coastiejoe]

My shoe looks like someone had been attempting to add sealant to the perimeter.
Is it really as difficult as I have read to correctly replace the seal for that?
Is "the right stuff" the best to seal around that as well?

They are no fun, but do need to be done right. They will leak for sure if they are not. You basically need to remove it, prep EVERYTHING and then put it together correctly.