Boat Builder Central - Builder Forums

I launched my C19 (see launchings) just under 3 weeks ago and am really happy with her - she may be slightly heavier than planned (whats new there) but she is amazingly stable (even compared to my old OD 18); my only concern is when I corner I have to power back as the prop seems to overspeed in a turn. I don't know if it is cavitating or what, but the rpms increase rapidly and the turn is rather slow - not slipping just cant power through it.

Will dropping the engine a few notches help?

Getting 5250 rpm on a 2002 evinrude 90 Ficht ram...

Probably so. I'd only move it one notch at a time though. Does the engine have power trim? What happens if you trim it down a little before the turn?

It was trimmed fully down. Dont know if a dolphin fin on the engine might help. At the moment engine it is set about 2 inches above the keel - maybe thats a bit much.

What prop are you running?

I was able to avoid lowering my engine on the seacraft by going from a three blade to a 4 blade, 4 blade had MUCH more bite.

Rpm's seem low , pretty sure that engine should be a lot closer to 6000 , 6200 rpms . Check the engine
spec's .

According to this your RPM's look OK.

http://pdf.nauticexpo.com/pdf/michigan- ... 37-_8.html

I have a similar effect with my P19 on sharp turns which I am sure is cavitation. I believe that most of the problem comes from the skeg ending too close to the stern and messing up the flow over the prop. When I repaint the hull this Spring I intend to cut back the skeg and shape it to improve the flow over the prop. Dropping the prop may also cure the problem, but I hate to draw even an inch more water than necessary in the gunk holes I like to visit.

So the engine rpm should be about 5250 to 5750 - in a sharp turn at speed if I don't pull back on the throttle it will overspend above 6000... And it sounds horrible!

Joel - Prop is the standard aluminium evinrude 3 blade. ericsil - does the p19 have a skeg? My c19 doesn't but it does seem that there is sort of an eddy of white water as you corner between the edge of the transom and the engine - maybe cos the boat is quite wide.

I don't mind loosing a bit of draft if that would cure the problem

I've had similar issues on my last few boats. It wasn't cavitation, that's a whole other issue, it's most likely your prop is blowing out. Basically your prop is losing bite in the turns, this is very common with stock props and a raised motor. Lowering your motor will help, but ultimately you will want to find a better prop. If you get a good prop with some decent cupping on it you should be able to keep your motor at it's current height.

Also I've learned to try and get a prop that will keep you towards the upper end of your RPM range when lightly loaded. If not when you load down the boat with people and gear your RPM's will drop below the range and you will be lugging the motor which will shorten it's life.

This is just my experience, others may have found different solutions.

A stainless 4 blade will probably solve that problem, they "bite" MUCH better.

Im sorry, I did not catch the part where you mentioned it was 2" above the bottom of the boat, thats pretty high for a motor hanging directly on the transom. I would still try a 4 blade though