Maximum inboard prop diameter

[Fr. Frank]

With a nicely shaped 3b 16x16 and a 260 hp motor, you should cruise at 20 kts, and top out at 28 kts, depending on a whole lot of stuff.

But the unvarnished truth is that you're not going to touch 40 kts without at least 500 hp, (and probably not even then) simply because of your angle of thrust.

Too much wetted surface=too much drag. You'd have to fair your tunnel, then extend the shaft and rudder out of the transom to get the thrust angle within about 2-3 degrees of your keel line. Too much continual stern lift results in too much forward water displacement resulting in too much drag.

I knew a 23 inboard in North Palm Beach that was repowered in the 80's with a 375 hp small block, and she topped out at 31 kts, or 36 mph. That long-duration cam sounded great, and it nearly jumped out of the water from a stop, but the laws of physics still prevailed.