FAQ - Kitty Hawk 26
1) Can I power the KH26 with twin 150's?
The KH26 was designed around a single Honda BF225 outboard with a weight of around 620 pounds. The new 4 cylinder Yamaha F150 weighs about 491 pounds. That gives a weight of 982 pounds. This weight will put the stern of the boat down about 1 3/8" deeper in the water. The bow will come up about 2 1/8". This isn't too bad and would likely work out alright (No promises!), although we would need to test a boat to confirm. We would also have to redesign the transom cutout in order to get the engines at the correct height.
With twin BF 225's, the stern would go down 2 3/8" and the bow would go up a little over 3 5/8". That is entirely too much trim disturbance as far as I am concerned and I would not recommend it. The other issue with this much power is hull shape. The KH26 is a moderate V hull with only 12.5 degrees of deadrise. The KH26 really isn't designed for the high speeds you'd hit with that much power.
2) Can I install an outboard bracket?
A bracket will move the weight of the outboard aft about 30". When you calculate the trim disturbance of a weight, it is actually a moment measured from the Center of Buoyancy of the hull. If the outboard weighs 620 pounds, then we have an additional moment of 1550 ft/lbs. On the KH26 this will sink the stern down by about 5/8" and the bow will come up about 1". Not too bad and should work fine. Twin F150's will put the stern down by almost 2 1/2" and bring the bow up almost 3 3/4". That is way too much trim disturbance and could lead to poor handling and poor low speed planing performance. Lets not even discuss twin V6 outboards on a bracket! I have not done any drawings for a full transom, yet . . . so you would be on your own at this point.
3) How about a straight inboard? I have an old 6-71 Detroit laying around in the back of my shop.
The KH26 was originally designed for a straight inboard. The engine was under the console with a straight shaft. The issue was underwater hardware, namely the strut. I looked everywhere and just couldn't find a stock strut that would fit. My attempts to find someone who would cast one for us were also frustrating. As I am not comfortable with welded up stainless struts, we then switched to sterndrive power. That led to the current outboard design which really simplified things. I still have the preliminary inboard drawings, but with outboards being so reliable and efficient these days, I think the reasoning behind using an inboard on this size boat is getting a lot less sound. Outboards are easier to build, faster, more efficient, quieter and smoother running. As for that old Detroit, please send it to be melted down into something more modern and useful!
4) How about an express version with a cabin up forward?
The bow of a Carolina style boat is a very small space. With a flush deck and just a raised portion aft, there really won't be much room up there to do anything. If you want an express, I think you should be looking for something in the low 30 foot range, maybe with a 10'-11' beam.