Over 12 years ago my 1976 15hp had same problem. We installed a new
impeller, new themostat. Then only a drip out the peehole and still
overheating. Finally found the little o-ring at the top of the water
tube had crumpled and blocked the flow going into the head. This is at
the base of the head where your watertube from the foot inserts.
Get the Clymer Manual (B732)from Carquest Auto, excellent book.
Tough engine, still strong today, went 12 miles yesterday in salt,
don't replace! Give to me if you do.
Bill Mc


Greetings:

I have a second one w/ low compression in the garage also, so...if you need
parts, let me know.

BL