Okay. I got 3 estimates on replacing the transom. Each has one set assuming: (a) I did all the de-rigging and re-rigging, and one set assuming (b) I pull the boat in as is and they do all the work.
All estimates included raising the transom to either 25" or 30", and glassing in the through-hull deck scuppers, and having the deck drain into the bilge. Mercury makes a both 25" and 30" drive shafts, shift shafts, and water tubes for my 90 Optimax, and I would have to use one or two 5" mid housing adapters, about $300 each plus studs. Either that or repower with the appropriate length motor.
(I really like the 350SCi Verado)
With me (200 lbs) standing in the back, I currently get about 3/4" of water on the deck with the drains open. And they leak into the bilge now.
Shop 1: using marine plywood
A = $2,100
B = $3,700
Shop 2: using Coosa
A = 2,250
B = 2,900
Shop 3: using either
A = $1,800 with plywood, $2,100 with composite
B = $2,500 with plywood, $2,800 with composite
FTR, the last transom replacement has lasted 26 years, using plywood.
__________________
Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.
Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!
Currently without a SeaCraft 
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury