Motor height on a tunnel hull

[Brifish]

I recently purchased a Mercury 20hp for an old river hawk b52. It has a tunnel hull , do I line up the cavitation plate with the top of the tunnel? Seems kind of high. I would like to test it the way it sits, which is about halfway in the tunnel. Also I’d like to mount it on a cmc pt 35, but I’m afraid that the set back might complicate the mounting height. If I have to use a jack plate then no power trim. I didn’t want it on the motor itself because the ram stops the motor from kicking up if you hit something. Any information would be greatly appreciated,thanks.

 

[JROESEL]

Man that thing ought to scream in some shallow water, I would try it, the way you have it set up now, see what performance you get, a hydraulic jack plate would make a lot easier for you, leave down in deep water and raise up shallow water

 

[RedHills]

Think it's too deep now. Plate should be closer to top of tunnel.

 

[little rascal]

Also I’d like to mount it on a cmc pt 35, but I’m afraid that the set back might complicate the mounting height.

The farther the set back, the higher u can go. A good 4 blade prop with some more cup will help it hold and grip better in turns and chop.

 

[hipster dufus]

Its a 20 hp. Tweakin is a waste, just run it n fish

 

[Lukikus2]

I would raise the motor up until the prop is in the center of the tunnel. The tunnel is designed to direct water to the motor in shallow conditions. You will not have a good hole shot but will be able to run a lot shallower than other boats.

 

[Brifish]

I’ve been busy lately, just checked in on this post. Thanks for all the great info! I’m gonna run it the way it is just to see what happens ( I gotta break in the motor anyway) but I think y’all are right about moving it up. I like the hydraulic jack plate but I’m kinda stuck on stupid about the power trim, my thinking is that it’ll help adjust to the conditions when I’m on plane. I just did some glass work on the inside,changed the layout and reinforced it , poured some foam down the center to flatten the deck. That thing was a little flimsy and I didn’t want to run it at speed like that, plus there was water in all the foam.