Seeking guidance on design of 18' cat-ketch double ender

The transom issue is a bit tricky. If you want it so you can mount a small outboard, like a 1 cylinder 3 hp, then you want to be able to sit back there and access the controls for it. Tiller extensions for the OB are an option, but would really clutter up the looks of the boat. An alternative that I use on canoes is to build a side bracket for the hull that puts controls where I can get at them from a normal sitting position. I cant the OB leg under the hull as much as I can. So in my world, a transom that is less than about 3.5 feet wide doesn't work for even a tiny OB mount because you can't sit far enough aft to use it. The good news is that at 18 feet and 1000 pounds, there is enough boat to work with and do it either way.

The third option is an OB in a well. It's tedious to design and build and use, but it does work. And occasionally even looks pretty good. For design purposes, allow for at least a Mercury 6hp with 9.25 dia prop.


Photo - https://downeastboatforum.com/threads/outboard-boat-with-a-well.19069/post-191219

The boat - Handy Billy 18' https://www.harrybryan.com/products/handy-billy-18

philSweet said:

The transom issue is a bit tricky. If you want it so you can mount a small outboard, like a 1 cylinder 3 hp, then you want to be able to sit back there and access the controls for it. Tiller extensions for the OB are an option, but would really clutter up the looks of the boat. An alternative that I use on canoes is to build a side bracket for the hull that puts controls where I can get at them from a normal sitting position. I cant the OB leg under the hull as much as I can. So in my world, a transom that is less than about 3.5 feet wide doesn't work for even a tiny OB mount because you can't sit far enough aft to use it. The good news is that at 18 feet and 1000 pounds, there is enough boat to work with and do it either way.

The third option is an OB in a well. It's tedious to design and build and use, but it does work. And occasionally even looks pretty good. For design purposes, allow for at least a Mercury 6hp with 9.25 dia prop.

Photo - https://downeastboatforum.com/threads/outboard-boat-with-a-well.19069/post-191219

The boat - Handy Billy 18' https://www.harrybryan.com/products/handy-billy-18

Click to expand...

I was thinking a side bracket like Ed Sturgeon has on his no man's land boat. I'm no stranger to a Mercury 6hp. In a former life, I used to drive a Mako across Florida Bay to the edge of the Everglades and throw one of those on the back of a Jon boat to go further up in the mangroves. I'm curious to see how the electric offerings evolve. A couple of batteries would make good ballast. Whichever motor I get would not live on the bracket.
Do the redrawn lines look more reasonable or do I need more submerged volume aft?

An outboard well not only takes up a large percentage of cockpit sole space but is in the way whether or not it is being used.
Others will have a more charitable opinion.

Yes, I was trying not to oversell that option. I just don't like stink pots hanging off cute boats. The side mount is less visually annoying and you can ship the entire mount when not wanted. But with a very fine stern, you can't do much with the aft three feet anyway.