how to change thermostat?

[redneck88]

ive got a 140hp 1981 evinrude sport and my over heat alarm has been going off,ive changed the impeller and it still does it and the tell tale isnt very hot either,so my next step is the thermostat but i dont know where its at or what i need to do to change it out so any info would be greatly appreciated.

 

[55'Fleetwin7.5]

Re: how to change thermostat?

I just "examined" mine on a 4 cyl 90hp from 1965. It was located in a housing on the rear of the power head.. between the cylinders.. with large hoses coming into it from both sides. I removed 5 or 6 bolts from the top... careful, there is a pair of springs inside..(mine anyway)...Hope it helps,

Tom

 

[55'Fleetwin7.5]

Re: how to change thermostat?

You could also have a bad sending unit... might be giving the impression your very hot when you are actually not. Are your cylinder heads REALLY HOT? There are heat crayons that you can use or an infrared thermometer... My engine when warm, should be around 168 degrees... i believe...

Hope it helps,

Tom

 

[ken52]

Re: how to change thermostat?

I have a 87 140 and should be similar, if you follow the hose from the teletale back up it should go to the starbord side first then to port side. They are small blocks with 4 bolts each side. Very easy to remove and clean out. Any blockage there could cause the alarm due to water restriction.

Others with more knowledge here may be able to add more or different things to check. Just sharing my experiences.

 

[Vic.S]

Re: how to change thermostat?

The diagram HERE shows the thermostats and the pressure relief valve (2 of each) Enlarge it fully to view and the assembly concerned is at the top.

#78 is one of the thermostats and #76 is one of the pressure relief valves.

Dismantle it all carefully noting the position and orientation of all the parts

But before you wade in there be sure it really is overheating.
The thermo crayons are a good idea. Some multimeters take a contact thermometer. Or you should be able to touch it and keep a finger on the cylinder heads for a couple of seconds or so but no more.

 

[redneck88]

Re: how to change thermostat?

im positive that its over heating it started smoking or steaming really bad last time i took it out so i shut it down to let it cool down,thanks for the help.