I had an '88 Winner 18' bass/ski boat with a 150hp Merc that I bought brand spankin' new, and kept for 4 years before selling.
I lived 2 hours from the (then) inlaws at Lake Anna.
Never had a problem with it.
The last year I had it, it went in the water twice in the season.......so I sold it.

 

While I don't have much knowledge on sterndrives (I/O), heres a forum with plenty of knowledge. It's like the DTR of boats! A number of members there helped me find info and advice on my old 72 Johnson (OMC) 6HP that I am rebuilding. Top notch forum.

http://forums.iboats.com/

 

Before you tear into anything verify what the exact problem is. If it needs the 3 bellows then that in and of itself is not that bad of a job. If it does indeed need a transom plate reseal then you will undoubtedly have a lot of rot in the plywood sandwiched in between the fiberglass of the stern. You can check this by having the drive raised all the way up, then just grab it and try to move it up and down. Look for any flexing in the fiberglass stern, if there is flexing then there is substantial rot. Once the rot is in the wood it is a cancer and just keeps spreading.

Couple things to know, the Ford engine came in two configurations, counter clockwise rotation (ccwr) and clockwise rotation, (cwr). It will have the engine rotation on a sticker on the air cleaner. The drive will be a 1st gen Alpha One.

Let us know what you find out.

 

I live 9/10 mile from a very nice lake, and there's talk about turning a coal mine into a new state park, and if that happens I will be about 200 yards from a lake.

 

BOAT= Bring Out Another Thousand.
My buddy has a 24' welded aluminum Boulton and its sweet. A sticker on the dash reads "This Boat Runs on Gas, Not Thanks."
I don't mind buying gas 3-6 times a year for it and not have any of the other issues associated with costs of owning one.