23' twin engine blowout problem

[TonyS]

I have a 1986 SeaCraft walkaround cuddy, with twin 1988 mercury 135's. I have a problem with the props blowing out around 2000 to 2300 and I have to slow down or pick up speed till they bit.
I was told the engines sit to high on the transom. The engine have 25" shafts and are mount all the way down. Can anybody HELP.

[Hooper]

Tony,

I am no expert by any stretch but I run a 25" shaft on my 23' CC. I have a single outboard, a Mariner, and it gives me no trouble, I am thinking, with twins, they would sit more outboard from the keel thus the hull bottom should be drawing less water than at the keel right? Strange problem...but, I think that somewhere in this site, someone will have a suggestion for you. I bet someone has had that problem before and can correct it. Sorry I cant help you more....Gordon

[TonyS]

Hooper, Thank you for your reply. I forgot to say that my center line on the transom is 31"s, I think the boat built in the 80's had deeper center line then the early ones. Your boat may be more of a classic then the one I have. But I LOVE MY BOAT.

[Scott]

Tony and Hooper welcome to the site!

Tony like Hooper says I'm no expert but your not getting clean water for some reason....I would however be inclined to think that if you have a 30" transom with twin motors with 25" shafts your good. There’s a lot of stuff you could look at.

Thru hull / Transducers causing turbulence in front of the props?
I would guess that you've made sure the cavitation plates are on the same plane with the bottom of the boat?
What about the props are they the right ones for the motors.... pitch??
Have you messed around with the trim while running?

The only time I've experienced this has been when air has gotten under the boat and the props got caught in the wash.

Not alot of help but some things to consider if you havent already..
Scott

[TonyS]

Scott Thank you, I tried everything you said. I think the one thing I did not try, is a new setup. The engine cavitation plates are 1" above the transom. Do you know the proper setup. (spacing and transom hight).

[Scott]

Tony

My engine is about even (a single) with the bottom. You wouldn’t want to go higher than that(the 1" even though I don’t think that’s too high) but if you could lower the engines a little it wouldn’t hurt......just more drag. Doesn’t sound like that can be done though [img]images/icons/confused.gif[/img]

Trayder ... where's the cavitation plates on the Contender??? or anyone else???

Has the boat always done this.....and does it do it when on plane??