Tunnel Prop Question

[big-boss]

I am going to repower an old 27ft Uniflite with a cummins and about a 20dia prop. I do not want to loose all the draft with a propeller sticking down. Can a cut a "tunnel" in the bottom of the transom and tuck it under without loosing efficiency? I do not have much engine compartment this tucking up would also help with the angle off the back of transmission.
How would I design this? Thanks

[Olav]

big-boss,

you can download a very interesting paper on propeller tunnel design from Donald L. Blount and Assoc., Inc. (http://www.dlba-inc.com/photos/pubs/18.pdf).

Maybe this is of some help...