Do I have a cavitation problem? I really don't know.

[marcuskeeler]

Hi Guys.
I've owned PWC's a long while but my boats have all been traditional stern drives.
Well recently we bought a sportster 4-tech, a long story but it was tied up for the longest time in a horrible divorce settlement before sitting idle in a garage for ages. It's a 2004 but a time capsule, utterly mint and with 25 hours on it.

Anyhoo, it runs beautifully, motor is sweet and starts on the button, no reason to doubt it. My query is one about cavitation.

if I go WOT on the gas from a standstill the motor races, touches the rev limiter and essentially cavitates until it works up enough speed to plane and take off. The process is easier and somewhat more efficient if I feed the gas in progressively.
The problem is amplified with more people in the boat of course.

So, I don't know. I'm used to stern drives which don't do that and I have loads of hours on PWC's which don't do that in my experience either.

If the boat had a whole bunch of hours on it I'd think the wear ring or impellor was suspect but.....

Is this just normal behaviour???

Thanks

 

[Seadoobuddy]

Hi and welcome to the forum.

Even a boat with 30 minutes on it could cavitate if the PO sucked up something through the grate.
check the clearance between the tip of the impeller and the wear ring. Should be less than .040 inches....use a feeler gauge.

 

[ID62]

Hi, just my experiance....
First speedup the boat in a moderate way (approx. 15-20 km/h) and then it will be fine for the top speed ;-)
I figured out the same issue....

best regards from Germany
Ingo

 

[marcuskeeler]

OK So I got under he boat to inspect the impeller. It's absolutely MINT, not a mark on it and the clearence is barely enough to get a feeler gauge in. Definately supports the 25hours useage.

Only thing I notice is the blades look like they have been sharpened, is that a factory thing?

 

[cheappc]

OK So I got under he boat to inspect the impeller. It's absolutely MINT, not a mark on it and the clearence is barely enough to get a feeler gauge in. Definately supports the 25hours useage.

Only thing I notice is the blades look like they have been sharpened, is that a factory thing?

I just bought a brand new one, and there is a "slight" wait for it to plane, not as bad as my old one, but is there, it takes me about 5 seconds to get a good plane...

just my .02 cents..

 

[marcuskeeler]

I just bought a brand new one, and there is a "slight" wait for it to plane, not as bad as my old one, but is there, it takes me about 5 seconds to get a good plane...

just my .02 cents..

Yea, mine takes about the same, maybe a little quicker. Once I get up it's ok, I can reach like 48/49mph which I understand is about right.

 

[Macster]

5 seconds and red lining doesn't sound normal to me. I would think 3 seconds with one or two passengers to get on the plane. It only takes the slightest knick on an impeller to cause cavitation.