Sea Ray Sundancer 290 (1992) Outboard Re-Power

This article says a (spacing to aft) bracket (on already designed to be outboard) should increase efficiency because it lets hull work and props work better as more separate forces. At least now you got someone to quote to all the naysayers.

I'd guess that also goes for a stern/outboard conversion since stern-D looks kinda like outboards that are stuck into transom.

Unfortunately the article seems mostly flogging on brand, Anderson, and doesn't even dabble in any of the finer points of design that might get you some of that claimed 22% gain......

SO.....

you might want to include provision to "play with it" in pod design, as well as figure out WTF is going on with claimed gains.

I'm GUESSING it has to do with distance aft, and that is also at certain speeds. You want props not messing with hull by creating big suction before trailing edge of hull, but you don't want props in turbulence that happens soon after edge.

Also GUESSING that the big claimed gain only happens at fairly narrow confluence of speed and dimension, like a bulb-bow on ship.

Drill a pattern of bolt holes on the sides of Pod, and in side flanges of rear engine mount plate of Pod, top and bottom, and middle. That way you can leave top bolts in but loose, and swing bottom of flange (with engine still mounted) forward to new position, insert bolts, then swing top forward, insert bolts, etc. Or just add Unistrut and slide fore and aft.

https://www.powerandmotoryacht.com/maintenance/the-benefits-of-a-bracket-on-your-boat

Also cautions against using new Pod/Bracket space to put something heavy, since will effect trim. I'm thinking "but that might be needed, but maybe would over-stress connection".

 

I would be making a concerted effort to find a sister vessel that has undergone this conversion, it is a ticklish problem to know how high to mount the pod, and even if you drill the holes to allow for up or down adjustment of the final engine mounting height, you might still find it too high, or too low. Learning from the experiences of others can save a lot of grief.

 

Take a look at Armstrong Nautical in Florida (There may be an agent or similar fabricator in the UK). I was involved with a Bertram 26 (classic 70's boat)with pod (aluminum) mounted outboards replacing twin inboards (shafts) and it turned out extremely well. Came complete & ready to mount with instructions on how to assess & prep the boat for weight, balance, & structure, fit the pod, and follow-up work.
You have a popular and well built boat and I am sure Armstrong has done several pods for that model.