1987 50hp Evinrude E50TLCUD Thermostat Replacement

[FishAtFive]

The problem of it idling poorly after warming up has never went away and no matter what I've replaced/rebuilt the problem persists and frankly I am just done with it. This weekend I am pretty sure it got stuck closed because it lost all accelleration and the temp alarm went off. So here we go.

I'm going in, wish me luck. Will post updates here.

 

[racerone]

I see anew 4 stroke soon.

 

[FishAtFive]

I see anew 4 stroke soon.

Not even an option, the previous owner did a **** poor job on a through hull and the transom rot is up to one of the four mounting bolts.

 

[racerone]

Did you ever post the actual compression values on this motor?

 

[FishAtFive]

Did you ever post the actual compression values on this motor?

I believe so. If I recall correctly they were between 140 and 150 and +-10% of each other. I checked twice, when I first started working on it and after the last time it overheated. Disclaimer: crappy amazon tester used.

 

[FishAtFive]

All 14 bolts are turning except this middle one. I can see the head turning but springing back, which means it's not actually turning. I think I learned that from a Joe Reeves video. Got PB on it and now I wait.

 

[FishAtFive]

Got the last one out! Had it soaking in PB for about two days, plenty of light tapping with the hammer, and then I put some heat on it and came back a few hours later and it slowly came out. I'll take the head cover off tomorrow. I really hope to find the thermostat is indeed shot.

 

[FishAtFive]

Inspected the thermostat and only thing I can conclude is that it was stuck closed and the pressure relief valve must have gotten stuck closed as well or clogged, leading it to overheat. I don't know how those correlate to it going into a sort of "limp mode" before this happened. I had it full throttle and it was not ramping up, but after I let it cool down it ran ok. I thought the 1987 E50TLCUD did not have a concept of limp mode, and I don't know how the computer would even know there was a temp situation as it is not integrated with the temp sensor.

 

[racerone]

There is no limp mode on this motor.----There is no computer on this motor.

 

[FishAtFive]

There is no limp mode on this motor.----There is no computer on this motor.

Would a stuck shut thermostat and relief value cause it to bog down and overheat?

 

[racerone]

Thermal expansion of pistons jams / locks up / stops the motor.

 

[FishAtFive]

Thermal expansion of pistons jams / locks up / stops the motor.

Oh boy. Let me check the compression real quick. It did this immediately after drifting for about 5-10 minutes, and before that it was running normally.

 

[FishAtFive]

They are both almost exactly the same at 160 psi. Note - the last two times I checked it was not as high. Is this bad? Should I bother ordering the parts to fix the thermostat?