Evinrude 1991 140

[paul99]

Overheating indication. I had problems a few years ago with a faulty stbd side sensor and replaced it. Boat ran great for past 2.5 years. Problem has come back again on the stbd side again. I had it in to the local shop and they could not get it to duplicate (only happens under load at 4K rpm and above as near as I can tell). They replaced the sensor again and today I took it out. Alarm came in a couple of times. I checked it again and unplugging the stbd sensor stops the alarm(definitely stbd side is causing the problem). Compression checks are good @ 120 on all four. The shop guy thinks the head gasket may be leaking into the cooling jacket under load. Even when the engine is in alarm the temp on the water jacket does not seem that hot. A non contact pyrometer says the stbd is running at 168 degrees F. I have removed the t/stats again today and boiled them and monitored the temp. Both work fine, no corrosion, nothing.

Does anyone know if these are identical or not? One is marked 23FU (port) and the other is marked 23EU (stbd) are these temp ratings or what. Any help would be appreciated. By the way the water pump is good. It runs at 25psi by the console gage 4K rpm.

 

[DJ]

Re: Evinrude 1991 140

Overheating indication. I had problems a few years ago with a faulty stbd side sensor and replaced it. Boat ran great for past 2.5 years. Problem has come back again on the stbd side again. I had it in to the local shop and they could not get it to duplicate (only happens under load at 4K rpm and above as near as I can tell). They replaced the sensor again and today I took it out. Alarm came in a couple of times. I checked it again and unplugging the stbd sensor stops the alarm(definitely stbd side is causing the problem). Compression checks are good @ 120 on all four. The shop guy thinks the head gasket may be leaking into the cooling jacket under load. Even when the engine is in alarm the temp on the water jacket does not seem that hot. A non contact pyrometer says the stbd is running at 168 degrees F. I have removed the t/stats again today and boiled them and monitored the temp. Both work fine, no corrosion, nothing.

Does anyone know if these are identical or not? One is marked 23FU (port) and the other is marked 23EU (stbd) are these temp ratings or what. Any help would be appreciated. By the way the water pump is good. It runs at 25psi by the console gage 4K rpm.

168 degrees is too hot.

What do the spark plugs look like on the starboard side? Is either one, or both, real clean?

 

[DHPMARINE]

Re: Evinrude 1991 140

Yeah,you should be running 145 degrees or less.At 168 you most probably have some damage.Start with a compression test.

DHP

 

[HighTrim]

Re: Evinrude 1991 140

Since the compression is even across all 4, could it be an exhaust gasket leak, as opposed to a head gasket that the mechanic said? Is that what you were leaning towards if the plugs were "steam cleaned" DJ?

 

[flabum]

Re: Evinrude 1991 140

When was the last time you replaced the water pump?

Head gaskets are a possibility as is the base gasket. When you had the thermostats out, did they slide frrely in the rubber seats in the head? Those thermostats doulbe as pressure releif valves and if they hang a little on the rubber seats in the heads, it will cause a high speed overheat.


Also, when was the last time you changed the head gaskets? They should be changed every couple years if used in salt water.

 

[paul99]

Re: Evinrude 1991 140

I have had this engine for 7 years. The head gaskets have never been changed since I've had it. The plugs all look the same (checked after running in the driveway during flush out). I was expecting to see at least one on the stbd side to be steam cleaned (my mechanic did say that the compression gases could be leaking into the water jacket causing this intermittent overheating). I used a non contact pyrometer and at idle the port side is running 88 degrees F. THe stbd side is running at 112 degrees F. This seems very far apart. I'm leaning toward an obstruction of the cooling passages possibly. When I tested the t/stats they were smooth and the temp they operated at were consistent each time (no aparent binding etc.). I'm planning to pull the stbd head and have a good look around this week.

Thanks for the input. I'm not ready to turn this thing into an anchor yet!

 

[HighTrim]

Re: Evinrude 1991 140

If you still have the t stat out, I would drop the lu and run compressed air or the garden hose up it to ensure it exits at the t stat housing, then back flush it back down. Do this for only 1 tstat at a time to ensure both channels are clean. While the heads are off take a look at the water deflectors.