1975 25 horse power johnson thermostat

[tfishingnut]

Ok please dont beat me up, but i have been running my motor for 10 years now and have never thought about a thermostat at all. Well when I took the thermostat cover off I discover that there is no thermostat in there. My question is now , do I put a thermostat in or do I just leave it alone

 

[oldboat1]

Re: 1975 25 horse power johnson thermostat

Motor normally runs better with one (even temp.), but salt water running can be hard on them -- among other conditions. I've always run with t.stats. and just plan on changing them out if conditions warrant that. Usually easy to replace.

(can check online with your model number to see what's involved in terms of parts)

 

[tfishingnut]

Re: 1975 25 horse power johnson thermostat

Motor normally runs better with one (even temp.), but salt water running can be hard on them -- among other conditions. I've always run with t.stats. and just plan on changing them out if conditions warrant that. Usually easy to replace.

(can check online with your model number to see what's involved in terms of parts)

Yeah I have a new one and know how to replace it. Was just wondering if I replace it now if after 10 years of not having one, would it be bad on the cylinder walls because i heard once that running your motor without one would make the cylinder walls wear differently

 

[F_R]

Re: 1975 25 horse power johnson thermostat

Well, by "differently" if you mean "more", possibly. But if you mean that now using a thermostat would be a issue because of the wear, nah, don't worry about it.

There may be a lot of carbon build-up and some ring sticking from running without the stat, so a de-carboning treatment may be beneficial. Won't hurt, anyhow.

 

[oldboat1]

Re: 1975 25 horse power johnson thermostat

guess I would check back on the source info. to confirm or deny. If running OK without one for 10 years.....

 

[tfishingnut]

Re: 1975 25 horse power johnson thermostat

Ok, thanks.How do you do a de-carboning treatment

 

[Mohawkmtrs]

Re: 1975 25 horse power johnson thermostat

Look in the Top Secret files on the Johnson/Evinrude page.

 

[tfishingnut]

Re: 1975 25 horse power johnson thermostat

I am going to put thermostat in only i can't figure out where the seal goes that came with it. Does it go on top of thermostat and seal against housing cover or does it go under thermostat and seal against the opening that the thermostat fits into. I can't find any clear diagrams showing it.

 

[BigB9000]

Re: 1975 25 horse power johnson thermostat

Both.

The round seal has a grove inside. That grove slips over the T-stat.
To some, the T-stat is expensive. $25 + $5 seal VS tossing it out and calling it a day.
Seirra kits come with the seal though. (If I remember correctly)

This is probably what yours would have looked like, had it been there.
You can also see the seal wrapping around the T-stat in the pic.

 

[tfishingnut]

Re: 1975 25 horse power johnson thermostat

Well when I ordered it the list says one per assembly so i was confused as to whether it goes over or under the thermostat lip. Thanks for the help

 

[oldboat1]

Re: 1975 25 horse power johnson thermostat

Per BigB9000 above: For the thermostat shown in the pic, there is a grooved rubber gasket or ring around the housing of the t.stat (can see it in the pic). There is also a gasket to fit the shape of the cover (gasket appears not to be shown in the pic, although one could be in place.) Don't know what you have in hand, of course, or what list you are referencing.

 

[tfishingnut]

Re: 1975 25 horse power johnson thermostat

I see how it fits the thermostat now. Thanks everyone.

 

[tfishingnut]

Re: 1975 25 horse power johnson thermostat

View attachment 227220 Can someone tell me if I should leave the red plug in this hole when I put new thermostat in. I don't know if this was there when new or is it something the previous owner put in.

 

[tfishingnut]

Re: 1975 25 horse power johnson thermostat

Maybe this picture will be better