Cooling Problem with 1965 20 HP Johnson FD-19D

[Simfisg3618]

Restoring a 1965 20 HP Johnson FD-19D and have come across a weird cooling problem.

Engine heats to above 200 degrees when idling - have changed impeller and thermostat.

Place boat in the bayou and removed the thermostat and left the cover off.

Started then outboard and a stream of water shot 6 feet into the air -- so I know the water pump is working.

Placed the cover back onto the thermostat housing without the thermostat in place.

Started outboard and engine reach 200 degrees (reading with a digital pyrometer) in no time.

Thinking I must have an obstruction past the thermostat chamber -- no water coming out of the blow hole.

Anybody have an idea of what my next step would be?

Pictures attached.

Thanks,
Mike

 

[fdrgator]

So, no water at the blow hole, even with thermostat out?? That is weird. After leaving the thermostat chamber, water goes out the tube which you can see cast in the backside of the head, and heads for the exhaust housing and blow hole. It's hard to imagine that big passage being plugged up, but I suppose all things are possible. Starting with the 1968 models, there was a plastic restrictor in the water outlet, but that does not apply to yours. I suppose you are going to have to pull the head or powerhead for inspection. Decide which you prefer to do first. It's a crap shoot.