Glen-L.com

Ok here I come with what should actually be a GOOD question. Given that the boat I'm doing this on is a factory built plastic, please don't snub me. Anyhow here goes... I'm installing a "new"outboard on my 19' cobia. and have several conflicting views as far as alignment goes. Who has a REAL answer....What level is best for overall performance of the Anti ventilation plate in relation to the hull bottom. I have had responses of anywhere from flush to 3" below the hull.... and furthermore would this be measured at the certerline or at the outer edges of the AV plate??? Web searches do no good, the manufacturer sites are almost as bad, and marine shops give me the answers I already related.
PS I'm also finishing up a Hankinson Bullet and restoring a 64 CC supersport, the Cobia is the "everyday" hole in the water!
Thanks

A stock job puts it with the plate just under the hull. If you put it down three inches you will be putting more motor in the water and create more drag.

The whole idea here is for your prop to get a good bite in the water. So you want the water that is coming into the prop from the front of your boat as undisturbed as possible. Generally, the water directly under the boat hull is good water for your prop.

It is concievable that you have a funny hull or some type of fitting that sticks down in the water in front of the prop and screws the whole thing up. It's not likely, though.

Another thing that may change things is if you have a boat that planes bow high. That would tilt the hull in such a way, that you might have to lower the engine a little. If I had a boat like that, I would put a jack plate on it, then I could adjust the motor up and down easily and play with the setting.

Check out www.smalloutboards.com

He has an article on installing a motor and the relationship of the anti-cavitation plate to the hull bottom. I believe his answer is 1" or less below the hull bottom for optimum performance. Also, most engine manufacturers have recommended installations.

Robert

Your motor should have two sets of holes that you can put bolts through a slot so the motor slides up and down. Drill these holes so the cavitation plate is barely under the rear of the hull when the motor is down as far as possible.

Now, with the motor resting on the bolts mark the other two bolt holes in the second highest or highest holes and drill there..

You want most of your adjustment to be able to move the motor up. Now adjust the motor cavitation plate to 1 inch above the hull and bolt the motor.
Now go out and try it. It should work fine.

Thanks for the replies pretty much the consensus here seems to point to flush. Prior answers from local "experts" were all over as stated.