1961 Johnson Sea Horse 75 hp overheating

Clippership821

Petty Officer 2nd Class
Joined
Jun 26, 2007
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103
Whole new pump...Water coming out the back.....Could something be restricting the exhaust causing overheating? Water inlet tube? I'm at a loss.
Thanks
 

HighTrim

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Jun 21, 2007
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10,486
Re: 1961 Johnson Sea Horse 75 hp overheating

When does it seem to be overheating, at WOT, idle??
 

Clippership821

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1961 Johnson Sea Horse 75hp still overheating

1961 Johnson Sea Horse 75hp still overheating

Is it possible that the pump is functioning properly but water is not getting up to the heads. I just put in a complete pump kit and it seemed to be cooling fine. Water coming out the back and all. There is a lot of moss material in the water by the launch. Is it possible some of that could've got into the water intake? Thanks
 

tashasdaddy

Honorary Moderator Emeritus
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Re: 1961 Johnson Sea Horse 75hp still overheating

Re: 1961 Johnson Sea Horse 75hp still overheating

possible, also the thermostat may not be opening or clogged.
 

Chris1956

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Mar 25, 2004
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Re: 1961 Johnson Sea Horse 75 hp overheating

Clipper those two 3/8" short hosesat the bottom of the heads carry the cooling water to the thermostat box. Open up the box and check the passages are clear and see that water flows thru the heads.

Those thermostats can and do break. I ran my '58 fat-fifty for years without one.
 

Clippership821

Petty Officer 2nd Class
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Jun 26, 2007
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103
Re: 1961 Johnson Sea Horse 75 hp overheating

Thanks would it be a good idea to put a tell-tale on the top of number 1?
 

HighTrim

Supreme Mariner
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Jun 21, 2007
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10,486
Re: 1961 Johnson Sea Horse 75 hp overheating

there is a very good tell tale sticky at the top of this forum by IWombat. Worth a read. I would clean the intake area and have a look at the t stat like TD said.
 

Chris1956

Supreme Mariner
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Mar 25, 2004
Messages
28,103
Re: 1961 Johnson Sea Horse 75 hp overheating

Clipper, I do not remember if those motors had any plugs in the heads that would serve as a telltale.

You could rig up some kind of plastic tee in the hose from the head to the thermobox. That would be a good telltale, althought it is only pressurized to 10 psi, if I remember correctly.
 

Evinrude Boater

Lieutenant Junior Grade
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Jul 6, 2004
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1,144
Re: 1961 Johnson Sea Horse 75 hp overheating

My 64 Evinrude has a plug. I'm planning on installing a tell-tale.
 

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