Overheating Alarm at WOT 1992 Johnsons J140TLANS 140HP

[mricco]

2-stroke v4 johnson J140TLANS 140 HP
Replaced water pump and impeller (with full kit)
replaced inline fuel filter and primer bulb
replaced spark plugs
replaced thermostats
replaced head gaskets (they were in bad shape)
water jacket looked free of any obstructions
stream from telltale is not very tight. its a continuous stream but not a solid tight stream.
equal compression on cylinders
achieve WOT with all carbs

boat will idle just fine no alarms

at WOT boat will haul ass for about a minute then the continuous alarm sounds. ive tried to prime to rule out fuel restriction but the alarm stayed on. im getting readings at about 170 degrees Fahrenheit on the head when in gear but no throttle. Port side runs about 5-10F cooler.

Pulled thermostat housings and ran on muffs. Port side stayed around 115 and STBD side got up to about 130. there was smoke (or steam maybe) coming out of STBD side housing with water. seemed like a little bit more water would come out of Port side. Any advice what to try next?

 

[saltchuckmatt]

2-stroke v4 johnson J140TLANS 140 HP
Replaced water pump and impeller (with full kit)
replaced inline fuel filter and primer bulb
replaced spark plugs
replaced thermostats
replaced head gaskets (they were in bad shape)
water jacket looked free of any obstructions
stream from telltale is not very tight. its a continuous stream but not a solid tight stream.
equal compression on cylinders
achieve WOT with all carbs

boat will idle just fine no alarms

at WOT boat will haul ass for about a minute then the continuous alarm sounds. ive tried to prime to rule out fuel restriction but the alarm stayed on. im getting readings at about 170 degrees Fahrenheit on the head when in gear but no throttle. Port side runs about 5-10F cooler.

Pulled thermostat housings and ran on muffs. Port side stayed around 115 and STBD side got up to about 130. there was smoke (or steam maybe) coming out of STBD side housing with water. seemed like a little bit more water would come out of Port side. Any advice what to try next?

Not sure I'm the right expert here but I believe each side should read the same, heat wise. Sounds to me that you have some blockage somewhere. My brother had problems with something called "popoffs" which affected his alarm and cooling. So maybe research and see if your motor has those. I believe it a spring loaded mechanism that opens up more water at higher rpm's. Good luck.

 

[mricco]

Not sure I'm the right expert here but I believe each side should read the same, heat wise. Sounds to me that you have some blockage somewhere. My brother had problems with something called "popoffs" which affected his alarm and cooling. So maybe research and see if your motor has those. I believe it a spring loaded mechanism that opens up more water at higher rpm's. Good luck.

thanks for the insight. the poppet valves are actually one in the same as the thermostat on this outboard.

 

[saltchuckmatt]

thanks for the insight. the poppet valves are actually one in the same as the thermostat on this outboard.

Okay. My brothers was actually an Etec and the dealer could seem to fix it either. Finally my brother and a Evinrude local rep went out together and played around with the springs. I know it got fixed eventually I just forgot what they finally did. I wonder if it would be ok to run it without thermos and see what happens. (Bad thermostat maybe.) Did the engine have this problem before you changed all those parts?

 

[mricco]

Okay. My brothers was actually an Etec and the dealer could seem to fix it either. Finally my brother and a Evinrude local rep went out together and played around with the springs. I know it got fixed eventually I just forgot what they finally did. I wonder if it would be ok to run it without thermos and see what happens. (Bad thermostat maybe.) Did the engine have this problem before you changed all those parts?

You might be on to something. Yes the issues were prior to me working on it. My readings with the Tstat housing off we’re much lower than when they were on. Is that to be expected?

 

[saltchuckmatt]

You might be on to something. Yes the issues were prior to me working on it. My readings with the Tstat housing off we’re much lower than when they were on. Is that to be expected?

Well first off I'm confused. You say Tstat housing? I'm assuming you pulled the stat and bolted the cap back on. I believe the two sides should have the same temp reading. Sounds to me that something is partially plugged somewhere or worse. How's compression? Didn't you say the hottest reading was 170? And was that in a tank or muffs at your house? To be accurate you need to be out on the water (like my brother and the rep) for a condition like you describe. That motor should have one overheat sensor on each side. I guess it could be some sort of sensor failure but my bet is you have a plugged orifice somewhere or engine damage especially if your in salt water. Look for the spec on the alarm heat range...I think it's over 190

 

[mricco]

Well first off I'm confused. You say Tstat housing? I'm assuming you pulled the stat and bolted the cap back on. I believe the two sides should have the same temp reading. Sounds to me that something is partially plugged somewhere or worse. How's compression? Didn't you say the hottest reading was 170? And was that in a tank or muffs at your house? To be accurate you need to be out on the water (like my brother and the rep) for a condition like you describe. That motor should have one overheat sensor on each side. I guess it could be some sort of sensor failure but my bet is you have a plugged orifice somewhere or engine damage especially if your in salt water. Look for the spec on the alarm heat range...I think it's over 190

The cap on the housing off. Did not bolt the cap back on. Was told a slight variance shouldn't be an issue in temps but the stbd side had steam or smoke coming out of it so im wondering what that could be. This was on muffs. Compression is good. The 170 reading was on muffs in gear but no additional throttling. freshwater boat.

 

[saltchuckmatt]

You might be on to something. Yes the issues were prior to me working on it. My readings with the Tstat housing off we’re much lower than when they were on. Is that to be expected?

Forgot to answer, yes readings will be lower. One other thing to add, assuming this is a vro outboard the alarm is for both water and oil pressure/low tank. I forget now if the tone is different.

 

[mricco]

I’ve read that tone is more like a beeping. Either way it is disconnected and I’m using premix