cavitation plate and keel

[tuantom]

I'm in the process of mounting a Volvo 280 outdrive on the back of my boat that I just put a new transom in. The previous mounting had the bottom of the cavitation plate sit 1" below the keel. Now, I've read several times in the forums here that the keel and cavitation plate should line up.

Are the changes required to move this up 1" going to net enough performance gains to justify the work and hassle? Or could this be something done purposely?

The boat is a multi-purpose 1967, 285 HP, 23' cuddy-cabin (18˚ deadrise @ the transom) w/ 3 lifting strakes on each side (the inner-most ones terminating ~ 6' from the transom).

[tuantom]

I'm going to cut the new key-hole tomorrow. I can either use the original cutout in the exterior glass skin as a template; or move all the dimensions up 1" and do a little patchwork.
Just not sure of all the pros and cons of it - aside from the risk of ventilating my prop if set too high.

[Nojjan]

Hi Tuantom

I recommend you to stay with the anti-cavitation plate below the bottom (if it is a DP). Usually these duo-prop systems benfit more from having extra water than having a higher position to reduce drag. This is however only possible to really decide for each boat model through testing. Maybe you should trust the original builder, you will also save the work.

BR / J

[tuantom]

It's not a DP; but I'm sure you're right. Unfortunately, I don't have three or four models to experiment with
Besides, it always handled very solid and never ventilated the prop - Why risk it? So - the hole has been cut in its original location.