hot and cold heads

[Barracuda101]

while i was decarbing this weekend i noticed that the 2 port side heads were cold and the 2 starboard ones were hot. 1990 140 evinrude. the over heat alarm did not come on. i pulled the thermostat out to check it. it looked fine. i have never seen one that looked like that does not seem like any thing but an obstruction could prevent it from working. can i run it with the thermostat out to see if that is the problem. it has a new impeller and has a pretty good stream coming out. i ran it on muffs and run it in a big tank of water same results. i don't think it's over heating but it is still running a little rough at low rpm but does fine at high rpm. oh and by the way you guys were right when you said tell your neibors to close there windows during the decarb process.

 

[ezeke]

Re: hot and cold heads

You will need to open the thermostat capsule and remove the metal thermostat in order to test it. It sounds as though the port thermostat may be stuck open, allowing a constant flow of water. Be sure to note the direction so you don't reinsert the thermostat backwards.

The thermostat should open at around 143 degrees F.

BTW, the big bore looper 140 idles hot, but not so much as to set off the alarm. A lot of owners were uncomfortable with that and upgraded the thermostat system to be like the 1993 models. I still have the parts to upgrade mine, but it has never been a problem so it will probably just stay the way it came.

 

[wilde1j]

Re: hot and cold heads

Easy to test the stat ... pot of water and a thermometer. Put it in and see where it opens (should be ~ 145? F).

 

[dajohnson53]

Re: hot and cold heads

...

The thermostat should open at around 143 degrees F.

BTW, the big bore looper 140 idles hot, but not so much as to set off the alarm. A lot of owners were uncomfortable with that and upgraded the thermostat system to be like the 1993 models. I still have the parts to upgrade mine, but it has never been a problem so it will probably just stay the way it came.

At what temp. is the alarm supposed to sound? What temp would I see if I aimed an IR thermometer at it while idling on the hose? The reason I ask is that I noticed my 1990 V6 200 hp seemed to get pretty hot to the touch idling on the hose, but even after about 10 minutes no alarm. The telltale stream looked good. I had no reason to suspect any problem because the engine works perfectly in the water and I've never gotten an overheat alarm either in the water or on the hose. Normally I wouldn't even be thinking of this, but the other day it was idling with the cover off for a while and I just touched the heads out of curiousity.

 

[ezeke]

Re: hot and cold heads

In this engine, the temperature switches that controls the overheat warning closes the circuit and sounds a continuous alarm at 203? F. +/- 6?. The temperature switches also activates S.L.O.W. at 203?.
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The switch reopens at 170? F. +/- 15?. That is a range of 155? to 185?. That is the approximate range that my 140HP operates in when I am trolling at 2.8 MPH.
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The thermostat is rated at 143? F.​

 

[wilde1j]

Re: hot and cold heads

I had an '85 140 that ran a little cooler ... ~ 160? @ idle and 140?F at planning RPM's, but I had drilled bypass holes in the stat housing, BC without them, it ran way too hot.

 

[dajohnson53]

Re: hot and cold heads

In this engine, the temperature switches that controls the overheat warning closes the circuit and sounds a continuous alarm at 203? F. +/- 6?. The temperature switches also activates S.L.O.W. at 203?.
​

The switch reopens at 170? F. +/- 15?. That is a range of 155? to 185?. That is the approximate range that my 140HP operates in when I am trolling at 2.8 MPH.
​

The thermostat is rated at 143? F.​

Thanks. Just took a look at it with my el-cheapo IR thermometer, and at various places on the two cylinder banks I was getting 150-165 as far as I could tell. I seem to be getting some sort of interference (display says E2), but a temp does show initially. I didn't think of shutting the engine down and then checking - DOH - but I'm not worried. Seems everything is well within normal. As I've mentioned in previous posts, this is a new to me engine which I haven't used much yet, so everything is kind of new and I'm trying to feel comfortable with it. The engine felt pretty darn hot, but that is consistent with 150-160F - about 3 seconds on the touch test, more if a guy had tougher hands instead of the ones I have.

 

[Barracuda101]

Re: hot and cold heads

the thermostat capsule is plastic how do i open it?

 

[ezeke]

Re: hot and cold heads

The engine end is threaded into the rear section. You might need pliers.