temperature alarm on Yanmar 3YM30 in R21EC

[greenghost45]

Sometimes when trolling, the temperature alarm in the Yanmar panel goes off in my 2006 R21EC, which has a Yanmar 3YM30.It only happens in the summer time when the ambient water temperature is warmer; probably 15 to 18 C (in the 60s in F) where I live on Vancouver Island. I have the Heatercraft bus type heater and switching that on is enough to quell the alarm. But I am wondering if switching out thermostats may help? I have a new spare labelled 71 degrees C. I don't know what the current thermostat installation is rated.

I just rebuilt the raw water pump and the water flow through the exhaust seems fine. I am not sure if the engine is actually overheating, or I just have a too conservative sensor. I have been thinking about getting an IR temperature gun to get accurate readings off the engine. Wondering if anyone else has this problem or has suggestions?

Thanks in advance!

 

[Capt’nKarl]

Here’s my 2 cents. Here in Florida the summer water temperature is about 85 degrees F, 30 degrees C. Running my 21EC With the 3YM30 in the summer at 26-3000 RPM I never had an overheat alarm. I would suggest you check the exhaust elbow and raw water heat exchanger for partial blockage. Make sure the raw water water pump is functioning properly. You might try using barnacle buster to clear the system. Of course it could be the thermostat needs to be replaced.
Good luck,
Karl

 

[ameyer97]

Make sure water flow at low RPM out the exhaust is sufficient. When I had low water flow coming out of exhaust below 1500 RPM I recall having an overheat alarm go off after running at 2200 RPM cruising for an hour and then idling around in the bay for about 5 minutes with low water flow once I slowed down.


I resolved this by throwing her in neutral and revving the engine up to get water flow. Alarm went off in about 20 seconds and didn't come back on.

 

[bob daily]

Yanmar recommends changing the mixing elbow out every 250 hours or get it cleaned at a radiator shop. The mixing elbow in this model is very prone to carbon blockage. Also the water inlet to the elbow is famous for getting clogged first. One way to know if it's the exhaust elbow is the smoke out the exhaust starts to get white at running speeds. Hope this helps Bob

 

[greenghost45]

Yanmar recommends changing the mixing elbow out every 250 hours or get it cleaned at a radiator shop. The mixing elbow in this model is very prone to carbon blockage. Also the water inlet to the elbow is famous for getting clogged first. One way to know if it's the exhaust elbow is the smoke out the exhaust starts to get white at running speeds. Hope this helps Bob

Thanks for the suggestion. I will check it out.