'73 55hp won't cool

[Galaxie]

We have a '73 55hp. We recognized as it got warmer water would stop flowing from the exhaust manifold through the clear tube to the thermostat. So, we checked the impeller and confirmed it is pumping. Opened up the exhaust manifold and replaced the gaskets. We also replaced the head gasket. Still we have the water flow stopping after the engine gets warm. We noticed that exhaust is coming through the the clear tube. Any ideas?

 

[eurolarva]

Re: '73 55hp won't cool

First try running without a thermostat. It may be stuck closed. Also verify that the water tube is going into the grommet up to the head via the kingpin plate. It is possible to have the water tube miss this hole and still assemble the lower unit. Also verify the key is in the impeller and that the water pump is not worn or pitted. Is your impeller six or twelve blades?

 

[Galaxie]

Re: '73 55hp won't cool

Thanx. eurolarva, we've tested the thermostat and it is opening. When we disassemble the lower leg the water tube stays firmly attached to the kingpin plate. We ran water up the tube and confirmed it was getting to the water jacket at the exhaust manifold. We have a new twelve blade impeller and new pump housing and it's pumping like a hot damn! Is it possible that exhaust could be leaking past the inside exhaust gasket into the water jacket and creating pressure thus stopping the water from coming up?

 

[eurolarva]

Re: '73 55hp won't cool

You mentioned you replaced the exhaust gaskets. Are you refering to the port side gaskets or the ones under the powerhead? I believe there is a water bypass near the tstat and wonder if that is giving you problems. The gaskets above and below the kingpin went to crap on me and looked all chewed up. If you loose that seal down there the water may be leaking under the head back into the motor leg. Have you tried running motor in a garbage can with water with that clear tube off?

 

[Galaxie]

Re: '73 55hp won't cool

We replaced the gaskets on the port side. We have run the motor in a garbage can and did have it pump through the clear tube until the motor got to about 180 degrees. Then the water slows to a stop and steam and/or what seems to be exhaust comes through the tube.

 

[eurolarva]

Re: '73 55hp won't cool

Sure sounds like the thermostat. Try running it without a thermostat in the garbage can. It is possible you have the thermostat in backwards. If the motor runs without the tstat I would get a new one and a new plastic grommet for it.

 

[scotiany]

Re: '73 55hp won't cool

Has your engine been used in salt water? If so, you could have a corroded water pressure relief valve. I hope not but, it's possible.

 

[Galaxie]

Re: '73 55hp won't cool

The cover for the thermostat won't allow it to be installed backwards(cover is too small). When the engine is just started and cool we have had the clear tube disconnected and water is flowing from the exhaust cover and the thermostat cover. It is not untill it gets hot that the flow stops. The engine has seen as much salt water as fresh. Where is the water pressure relief valve located and would the rise in temperature at the top of the power head affect it?

 

[scotiany]

Re: '73 55hp won't cool

Valve is under the water jacket. I would suggest getting a Seloc manual. It has detailed instructions on the repair of the valve. It can be a real pain to fix.

 

[Galaxie]

Re: '73 55hp won't cool

We don't see this valve on the 55HP. It is on the 75HP though.

 

[Galaxie]

Re: '73 55hp won't cool

For some reason when this motor gets warm the water stops flowing. And this is before it gets to the tstat. We have replaced all gaskets up top. Is there a gasket at the base of the powerhead that could be allowing exhaust into the water jacket when the motor gets warm?

 

[eurolarva]

Re: '73 55hp won't cool

This may be your problem I hope not. When the powerhead is removed there is an upper gasket on the spacer plate that the powerhead sits on. When that gasket is removed there is a seal that the upper water tube connects to. This seal or grommet is what holds the water tube in place when the lower leg is off. If you replaced the gasket between the spacer plate and forgot to replace this gasket this could be your problem. The best way to test if the gasket is in there is to put the water tube in without the lower unit attached. It should be held snug on this gasket. If the gasket is not there the water tube will fall out if it is not held. I can scan a picture of this if you need it. Email me at ralgoetz@comcast.net if you are interested.

 

[Galaxie]

Re: '73 55hp won't cool

Thanx eurolarva, we popped the powerhead off tonight. Both gaskets were there and the tube was firmly in place, but the rubber grommet/washer was extremely compressed and the gasket around the tube looked compromised. We are thinking that water flows up to the powerhead, but once the exhaust pressure and temperature gets to a certain point it moves under the gasket and up past the rubber grommet/washer and into the upper water jacket. Does this sound feasible . We have replaced the lower gasket and grommet/washer around the water tube and will do the second gasket and powerhead tomorrow. Hope this works 'cause we're headin' for the lake this weekend and we don't want to rent a canoe . Let us know if you think the exhaust - heat - pressure theory is possible. Thanx.

 

[eurolarva]

Re: '73 55hp won't cool

Your theory works for me. I am good with the simple things. Yours is a bit more complicated. Hope it works for you. If water is flowing through the Tstat when the motor is cool I cant see how the port side exhaust area is a problem. I have had that area apart and cant see how water can get stuck in there when motor is warm. Good luck.