Re: 7.5 hp Ted Williams cooling?
I'd be cautious about putting any serious money in that outboard at all. They aren't much, even when they're running OK, and they typically don't do that very long. Given their age, their lawnmower engine origins, and the difficulty of finding parts, they'll $10 and $20 you to death.
You should be able to find a good working one for about $100, if you insist on using that type of engine.
Instead of throwing good money after bad, start watching your local Craig's List for a Johnson or Evinrude 5, 5.5, 6, or 7.5 hp outboard. All will outperform your single-cylinder whizzer. In my area, you can find the 5, 5.5, and 7.5 hp outboards from the 50s and 60s in the $200 range, complete with tank, especially at the end of the season. Parts are readily available, and they run smooth and quiet.
The 6hp models are newer, from the 60s clear through the 90s. About $350 to start for the older ones. They are sweet outboards, and will outperform the 7.5 buzzers all hollow. Easy to work on. Parts are available, and they make a super nice engine on a small boat.
Scroll down in this section of the forum and you'll find my post about finally selling off all my 1 cylinder off-brand outboards. I wasted two years trying to get one running decently, and often limped home on my trolling motor.
This year, with the 6hp Johnson, the trolling motor hasn't gotten any use at all...not even for trolling. Don't waste your time fixing what is basically a crappy engine, at best. Get a little johnnyrude and go fishing, instead. Seriously.
. The motor will start after 10-15 pulls (I believe carb kit in my future