Thermostat

leejacstu

Cadet
Joined
Mar 2, 2008
Messages
15
I have a 76 Evinrude, 25hp. It runs very well. The previous owner removed the thermostat. Will it hurt anything to run this motor without the thermostat installed?
 

Rick.

Captain
Joined
Jul 30, 2006
Messages
3,740
Re: Thermostat

Did the prev.owner say why he removed it? The motor is designed and engineered with the thermostat as part of the equipment necessary for optimal performance of the engine. I can't see it hurting to run stat-less but I would imagine the motor will carbon up more quickly and there could be a small reduction in performance as well. I would replace the stat at the first opportunity but I would not be afraid to run the motor until then. Rick.
 

leejacstu

Cadet
Joined
Mar 2, 2008
Messages
15
Re: Thermostat

He threw the old thermostat away because it looked corroded and he didn't want to run the risk of over heating the engine. It seems to run good without the thermostat, but it uses a lot of gas. Is there any relationship between the thermostat and fuel effeciency?
 

Harker

Chief Petty Officer
Joined
Sep 21, 2003
Messages
452
Re: Thermostat

A little. The thermostat allows the motor to run at optimum temp so that all the parts are expanding and contracting as designed. You could be dumping unburned fuel from a too cold motor...and unburned fuel makes carbon build up. Does it idle nice without having to choke it often?
 

leejacstu

Cadet
Joined
Mar 2, 2008
Messages
15
Re: Thermostat

It runs better on top end, it sputters a little when idling and on take off, but not too bad.
 

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: Thermostat

You should replace that 'stat ASAP, it is needed. Remember tstats control minimum temperature, not max.

Without getting into mechanical theory, the t stat is needed to keep the engine running at an optimal temperature, preventing severe damage to the piston and cylinder wall.

Some motors will actually overheat. The necessary cooling water from the water pump is never quite filling the block, hence the top cylinder overheats. Some cooling systems actually rely on that t stat for a restriction, since the water is exiting quicker than it is being replenished. Removing the stat is also horrible for a water cooled rectifier/regulator.

The rings will wear out quicker (not by much, but quicker none the less), and carbon will build up as already stated.

You have to have faith in the OMC engineers, they get paid the big bucks, and if the bean counters could have talked them into scrapping the t stat, they would have Im sure!
 
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