That is what I would be thinking. Jackplate, splashwell. Jackplates are a useful, beneficial toy.

When my transom starts going I'm going to to cut my bracket down to 18" and widen the chamber. Then it's getting a hydraulic jackplate.

Chaser.. I have a 77 MA and when I bought the boat the PO glassed two 2x6's together and cut the sides of the motor well out and put the 2x6's on top of the cut out for transom. The 2x6's went across the transom on the inside for additional support. Glassed the 2x6 to the interior of transom(access through boxes at stern) and glass to existing transom cut out. Makes for an additional 5" or so. Mine was still pretty strurdy, but I redid the boat this past winter and closed the transom in.

Manual or hydraulic jackplates just add more weight to the stern. Especially if you keep the 20" transom.

I agree about weight when it comes to 35-60 lb. hydraulic jackplates, but the fixed plates are light, 11-12 lbs. Maybe having a pair of 40lb batteries under the console would help offset the weight and setback.
http://m.westmarine.com/aHR0cDovL3d3...3D#description
That said a 20" transom isn't ideal.

I checked into the jack plate idea and I am not convinced it accomplishes what I want to do. It would get the powerhead out of the water further, which is good, but it does nothing for the actual transom height and keeping out water, I would still have to install some sort of splash guard for this purpose.

I talked with one of my tech's this morning and we have a plan to raise the transom. Shouldn't be too much work and my feeling from the input here is that if I don't I'll wish I had.

Thanks for all the prompt feedback on this! I'll be sure to take some pics of the process and post here when the boat is complete!

Many a person has scabbed wood right on top of an existing "good" transom without issue. I would want to get away from that 20" transom too if at all possible. Definitely look into that tub style splashwell that the guys are going googly for. Hermco's doing it up for some guys.

Which year 175 Mariner you going with? That old 235 weighed about 400 lbs. I believe.

The Mariner is a 1989.

Our plan is to build a rectangular section of plywood cored glass that matches the existing transoms construction, and is the size necessary to fill the transom area and raise it 5". We will glue that in place with Pro-Set epoxy. We'll then bevel back the surrounding outside skin of the transom about 6" and tab the part in. We'll also bevel back the inside of the transom all the way to the bottom of the well and along the sides of the well and tab the part into that structure also.

That sounds like a good approach. As long as your bevel is at least a 12:1 ratio to your laminate thickness, and 6" should be plenty, your seam should be very strong. I would use epoxy resin for the tabbing for its superior secondary bond, but some guys here might consider that overkill.

Dave

We use epoxy for everything except where it is prohibited by class rules. Its not overkill in my book, just better boatbuilding!

what kind of race program? kitesurfing? just wondering because that's what i do when it get's to rough for my seacraft.

Sailboat racing program. We manage a 65' racer/cruiser, a Melges 24, and our own F18 catamaran. And possibly soon an Open 50 canting keel race boat. There are plenty of times that we are on the water when its not very comfortable for anyone in a small powerboat! Also we will run Race Committee from the boat including setting and retrieving race marks.

Must sound like sacrilege to all the fishermen on this forum! I hope I am not banished!:)