I'm looking at a mid eighties twin engine 311 Formula that has some "high" moisture readings in the transom and off the chart moisture readings under the gas tank area as well as
some delamination in the same under the gas tank area on the bottom of the boat. It was suggested that it would be repairable, but I'm not going to be able to handle this job myself.
What kind of $$ would one expect to pay a shop to do this kind of repair? I'm guessing that the gas tank area would be the most urgent. Could I have the work done in two jobs,
first the gas tank area and then do the transom later? Or would it be more cost effective to do it all at once?

What year, engines, drives? How much under market? How nice is interior? How far you gotta go to see it, drag it home?

It should all be done at once, and I'd guess that it could suck up $10-20k pretty quickly. Also the lifespan on the rest of the rigging is due to be up such as gauges, trim pumps, etc.

I would approach it as a full restoration.

1000$ per ft of repair plus de and re rig

Having to pay someone to do it, probably more than the boat is worth. Pass.

So far as I can tell, the exterior is above average, the cabin area is excellent and all the upholstery is great except for some stitching coming loose on the sundeck/engine cover. The running gear seems great, but who knows about whether to
freshen it all up or not. The gauges are mint. But, I can figure the mechanical stuff out. I was mainly wondering about the rest. It would definitely have to be a super deal or I'm out. But I want to have some basic information about the
stringer/transom replacement costs before I get too much further into this deal.

Any estimated costs are going to be subject to what is found after the repairs reveal what cannot be seen. I would proceed with extreme caution and be prepared for higher than expected costs.

Even if it was free I wouldn't take it.

That will easily run into the 20k range to have it fixed right.

like said before, if you have to pay for this repair, more than the boats worth...does not matter how good it looks on the outside