Transom Retro

[Mr. Sandman]

adding a bracket also increases the "effective length" this plays into whatever performance issues. there are.

Further, not all brackets are the same...some provide substantial hydrostatic buoyancy very far aft and can compensate for the weight of bigger heavier engines,

If you are at trolling along without a bracket, with a big OB hanging on the transom your static trim may be too much bow up (stern down). A bracket that provides some buoyancy will make it more neutral by providing hydrostatic boost just where you need it. Some of them are cleverly designed so that when you are running along the flow separates at the transom and the bracket is essentially out of the water providing no wetted surface (drag)...but when you stop you get the added buoyancy from the static displacement of the volume submerged. Thus the engine weight does not pull the ass end into the water.
There is more to it than most people think.

[likwid]

No bracket adds "substantial hydrostatic buoyancy" it would have to be the entire width and pretty long to do so.

Most transom to bracket jobs look to just offset the extra weight of a 4 stroke, not add buoyancy above what it previously was. this is why the euro transom came about. more strength more actual buoyancy.

the classic mako site has some very indepth and educational threads about switching from open transom to closed with bracket. most of the best were nidacore jobs and rebuilding the ends of the stringers to accomodate big modern outboards.