Prop size?

kg9hfrank

Recruit
Joined
May 15, 2015
Messages
5
I am looking for some real help here folks. I am at the prop stage now on a newly installed 90 HP 2 cycle on Too Cute. See here for the URL of the past year.
http://electronicinstrument.com/toocute.html
Here is the problem. Since it was purchased used, I had the motor replaced.
My new to me motor works perfect, cav plate in line with the bottom of the transom. Boat drafts 12". I have a 13/14 on it now, and it had severe cavitation. I added a whale tale on it and that stopped the cavitation and the cav plate is about 1-2" below the water line when I am trying to get on plane.
It seems the more power I give the motor the more the engine "try" but never gets up on plane. The boat weighs 2000lbs without a motor. Figure 300 more with me and some additional items. Looking at the prop, what should I be trying?
 

ondarvr

Supreme Mariner
Joined
Apr 6, 2005
Messages
11,527
What you're experiensing is ventilation, not cavitation, they're are very different things but frequently confused with each other.

Sometimes on hulls with very little "V" the motor needs to be mounted a little lower to prevent ventilation.

I would drop down to an 11" or 12", many shops will let you try a prop and as long as its still like new you can exchange it for another one.
 

kg9hfrank

Recruit
Joined
May 15, 2015
Messages
5
Going to hit up the local place Tuesday. They take off Mondays here on the Chain of Lakes in Illinois.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
You need to go without the foil for now. Your just masking a problem.Foils can do strange things Can you lower the motor?
Is there anything on the bottom or transom that might disturb the water near the prop.
In the picture it looked like it planed.Does it get up on the water,respond to up trim?
13/14 You mean 13" diameter X 14 pitch? 13 X 14. A 14" seems like a good starting point?
Normally diameter would be a secondary consideration. but you may have to try a larger diameter. You also may need a 4 blade prop.
 
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