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96 Evinrude 112, new prop, same pitch, cavitation issues. What did I do?

T

Tim D

Member
Hey again, y'all have been great at helping solve problems. I have a 96 evinrude 112spl. It runs great but I just put a new prop(same pitch) but an inch smaller. Went from 14x19 to a solas amita 13x19 and now it's having cavitation issues. It seems to be at higher rpms or if your hard out of the gate from a stop. What did I do wrong?
 
I ordered it from overtons, you think they'll take it back? Any other prop company you recommend or you think solas is ok?
 
Michigan wheel makes pretty decent props.

So why did you change the prop in the first place?

Was the old one cupped and this one is not?
 
They're sending a new one, as a replacement. The old one was chipped and just looked rough over all. I've seen it cavitate a little before on take off if your really on it but never at higher speeds.
 
Out of curiosity. If the same prop just an inch in diameter smaller lets it do that would going one pitch up help it (19 to a 21) or would it cause the same issue. Or would trying to find a 14x19 maybe even a 4 blade, be my best bet since that's what it had and seemed to do pretty well. I've got the new prop but haven't put it on yet. I'm at work with time on my hands and brainstorming lol. Had to ask while it was still fresh in mt head.
 
The other thing is to double check your engine height while you're at it. Trim down the engine until the anti-ventilation plate on the lower unit is parallel with the bottom of the hull. Now, put a straight edge (ruler, level, etc) on the bottom of the hull and see where the plate is relative to the top of the straight edge. The plate should be even to about 1/2" higher than the hull. If the engine is significantly higher than that, it could explain the cavitation issues.
 
Ok so we took it out with the new prop last night. Unless my tach is broke, It'll shoot over 5000rpms and that's not at full throttle or trimmed up. Would this new prop make that much difference? I don't know what top rpm is now when I realized I was revving that high I backed off.
 
I feel like an idiot. Apparently according to the manual my max is up to 5500rpm. Sorry for the I'm still a green horn mistake. Sorry I haven't had a chance to get it out and all the way up to max rpms yet due to work and weather. I'll post as soon as I can. Btw how much difference is there performance wise from aluminum to stainless? Is it worth it?
 
Tim, I came to this thread late, that would have been my first question....RPM? Why the smaller prop? You NEVER want to allow the motor to exceed max rpm. Aluminum and stainless are the same performance if the pitch, dia, and cup is all identical. Don't hit a rock with a stainless you may see more serious consequences......aluminums are safer if you are in dangerous situations. I rebuild aluminum props, they are also lighter, of course and not as good for corrosive water. Note to Kevin, anti-cavitation plate "above" the hull?
 
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Reducing the dia will get you out of the hole quicker,but could also take Your WOT over the max revs for the engine.Plus,you lose top end speed.
What looks like a cavitation issue could be prop slip.(not getting a much distance purchase for each prop revolution.)
There is a fine line between boat weight and size of prop.There are usually a range of upto three sizes.
I bought an engine with a prop that was too big for my boat,it wouldn't quite get on the plane,or reach WOT
I changed the prop for a smaller one,and it cured both problems.
 
Good reading....
[FONT=Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif]http://www.mercuryracing.com/prop-school-part-2-terminology/[/FONT]
 
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