20" Yamaha Four stroke 90s are pretty common in Mass and 366 lb. Good on gas. Run a 13"x x15" 4 blade.

Thats a good one too, Fish Stretcher;) One of the locals here has one on his SF18 and he couldn't be happier.

Great help fom all of you,it's appreciated.The info on outboards is invaluable to me,as I've been into I/O's for the last 15 years or so.
I'm going to take a look at the boat again over the weekend to make sure that it doesnt need a total resto.If it's something I can use safely,I'm going to make him an offer.
Did they make the 20 sefari model with different transom heights??.For some reason I thought he told me that it needed a longer shaft outboard.That was a year ago however,so I may be confusing it with another conversation.

Yes, at some point they did make the transom for 25" motors (xl).

On the 18SF's- all the transoms we have seen in the 80's have come as a 25" height. The 20 may be the same.