THANKS
Overflow when priming is normal.
As to your water issue I’ve never had one of
these but I do have a picture (I think) of
your motor. It looks like it has a pump rather
than an impeller. Pump systems have 2 check
valves. Most likely one or both are dirty or stuck.
I’ve offered some guesses as to what you may
find. You seem to have the mechanical skills
to understand what you’ll find once you get in
there.
Tubs.
I took apart the water pump a bit. the piston is connected to a take-off from the drive shaft. it was clean and not scored. I put a bit of grease on it before I put it back in the pump cavity. At the base of the cooling water copper tube, there is a check valve/ball valve. this ball valve moved freely when rotated back and forth. I blew air through it easily one way but air was blocked going the other way. The filter screen was at least average in cleanliness with a light making it through from other side. I did not see another check valve. there is a fine crack in the check valve body but with the holding nut in place I think there is no issue.
everything looked OK so wondering if cooling water actually exits through the exhaust pipe along with the engine fumes; that would explain my not seeing it shoot out of what I thought was a little blowhole under the exhaust manifold.
it could be that the cooling system is working fine?
Ed Voll