1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

[kevinelt]

I am trying solve a problem with this motor there is water coming out as it should with a new impeller but the motor still runs extremely hot. I checked the thermostat and it still works (in boiling water). I even ran the motor without thermostat. Still too hot to touch and hot water coming out. I briefly ran the motor with the thermostat housing off and I saw water rise and come out. Removed head cover and engine side cover to look for blockage and it all is clear. What else could make this motor run too hot to touch? I have never seen a motor with water circulation run so hot. If you have some insight please post what you know.
thanks for reading

 

[AlTn]

Re: 1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

did you replace the head gasket and exhaust cover gaskets when you had them off?...inner exhaust plate show any signs or warpage or holes burned into it?...

 

[kevinelt]

Re: 1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

did you replace the head gasket and exhaust cover gaskets when you had them off?...inner exhaust plate show any signs or warpage or holes burned into it?...

I did not put motor back together yet. I intend to replace the gaskets but I did not see an issue with them or the inner exhaust plate. I did notice that the both pistons look like they might have gotten too hot before... corners at the top look melted . But the cylinders look good and the rings are lubed. This motor still has 105 psi per cylinder and usually starts on the first pull.

 

[Daviet]

Re: 1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

Where are measuring the temp, cylinder head, exhaust cover, engine block?

 

[kevinelt]

Re: 1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

The only thing I can think of that may be the problem is the 2-stroke oil I used to mix the 50 to 1 fuel... It has been sitting a while its evinrude/johnson xd-30 looks dark and smells funky. Could it be bad fuel/oil? have you used old oil before and had trouble?

 

[kevinelt]

Re: 1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

All three spots you indicated I touched. didn't use a guage to measure temp. Using old rule of thumb. If its to hot to touch its running too hot

 

[kfa4303]

Re: 1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

Is it pumping sufficient water? Perhaps the water uptake tube was misaligned after its last service.

 

[kevinelt]

Re: 1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

I intend to check that next. Last time I saw that happen on a motor no water reached the top or thermo housing this one does but maybe its just filling up exhaust leg and working its way up. What do you think about old 2-stroke oil does it go bad?

 

[F_R]

Re: 1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

Remove the powerhead from the exhaust housing. In the water outlet you will find part number 313435 water restrictor. It is made of white plastic and melted the first time it overheated. Sorry, it can't come back to life, you will have to replace it.

 

[kevinelt]

Re: 1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

Remove the powerhead from the exhaust housing. In the water outlet you will find part number 313435 water restrictor. It is made of white plastic and melted the first time it overheated. Sorry, it can't come back to life, you will have to replace it.

Thanks ... Thats the kind of info I been looking for.

 

[AlTn]

Re: 1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

when you get the powerhead back together and on the exhaust housing....lower unit removed....rig up a hose to the cooper water tube and open the faucet enough to give you enough water pressure to flow through the powerhead...start the engine and run it not above a fast idle...is it still overheating?..if so, you've still got issues on that end, if not, reattach the lower unit and test. Is the intake screen clear?...water tube fully in the water pump grommet?

 

[bonelessi]

Re: 1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

Remove the powerhead from the exhaust housing. In the water outlet you will find part number 313435 water restrictor. It is made of white plastic and melted the first time it overheated. Sorry, it can't come back to life, you will have to replace it.

Excellent!

 

[kevinelt]

Re: 1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

I did as you said. The restrictor was missing so I put in a new one. This motor still overheats quickly. Will this motor run hotter without a thermostat in it?

 

[AlTn]

Re: 1971 evinrude 25 hp is overheating regardless of new water pump. Please Help?

it's easy to remove if you want to try...when you tested it it should have opened in the 160 deg, range not 212 degs.

 

[Johnsb1]

What is the purpose of the restrictor?