Starboard Propulsion issues on '96 Speedster

[rgbradbury]

Hey guys,

I got this boat 4 weeks ago and I already have my first big issue, woohoo.

I was out tubing today and after about an hour of playing and a 30 minute rest, I fired the boat up to take it in. When I was pulling away, the right engine would only go to about 3500 rpm then cavitate heavily and the revs would then drop. I thought that I had sucked something up into the system. I got it to the dock using the other engine and had a good look around to see if I could locate the problem. I couldn't see anything in the pump, but I did see that the impeller boot had split and was coming out.

Got the boat home and took the pump off.

That is what I found.

Could this be causing the issue I was having? I thought that these things just kept water out of the splines. There didn't appear to be any damage to the splines on either the impeller or the driveshaft. Any ideas would be helpful.

 

[Dr Honda]

It's good you found it. If the grease washes out... you will destroy the splines. But... that's not where you cavitation is at.


I'd say that you are drawing air around your carbon seal.

 

[rgbradbury]

Thanks for the reply. I will definitely replace the boot, but I just don't know what was causing the rev issue. It wouldn't go past 3500 RPM, so I'm not sure that it was "cavitation", but I don't know how else to describe it. The revs would come up to 3500, but as I pushed the throttle forward from that point the pump would buffet and the then the revs would fall. So it wasn't like it was bouncing off the rev limiter and sucking air, but the pump was unable to keep a good flow. I'm just not sure that this little guy is the root of the problem, and I don't think the carbon seal was causing this either. Any other possibilities? Could the shaft have been binding up with this little rubber boot?

 

[Dr Honda]

If you have cavitation... it's like loosing traction in your car. The engine would rev high, and you just don't' go.

If it's dropping off, and trying to die... then there is a mechanical issue in the engine, or ignition. Since you are saying it's right at 3500 rpm... I would be looking at your neutral safety switch first.

 

[rgbradbury]

I guess that makes sense. Are there separate safety switches for each engine? Because the left engine works fine and revs up with no problems.

 

[rgbradbury]

So I got the new impeller boot and the little plastic ring that goes around it. Apparently the old one had just disintegrated.

Installed them along with some new grease on the driveshaft splines and tightened everything down. I ended up using the black silicone instead of the neoprene seal because it was all I could get on such short notice (need the boat this weekend for vacation).

The problem has disappeared. Not only does it rev up all the way with no buffeting anymore, but it launches out of the hole better than it ever has since I've owned it. I guess that boot makes a big difference when it's ripping itself out of its seat.

Great thanks for the input Doc and also thanks to Dockside Marine in Wilmington IL for having the little bugger in stock.