Yamaha 150 ETD overheat warning buzzer on muffs

[proftomda]

Hello All:

I have a 1991 yamaha 150ETD that issued a overheat horn and light while running on the water muff in my driveway. Engine was running at idle approximately 5 minutes while I was cleaning garage and appeared very normal with a healthy stream of water shooting out of the engine as always. As I approached the boat to climb aboard, I heard the overheat horn and immediately shut it off. I got my inferred temp gun and probed the engine and the highest temp I could get was 180 degrees. Let sit for 10 minutes, removed water inlet screen, turned on water and started engine again . This time no overheat warning and hottest temp was 124 degrees idleing at least 5 minutes.

Was damage inflicted at 180 degrees? Water pump impeller was replaced 10 months ago, maybe 10 hours on it. What should I be changing and or checking?

 

[99yam40]

Re: Yamaha 150 ETD overheat warning buzzer on muffs

Do not run it that long on muffs.
Some of the larger motors do not get enough water on the muffs

 

[proftomda]

Re: Yamaha 150 ETD overheat warning buzzer on muffs

Here's a update to my thread. I replaced both thermostats and the poppet valve this week with Yamaha parts. Fired the motor up today on the muffs and after 5 minutes at idle the temps were...Port side top to bottom 93,91,94 degrees F, starboard side 135,112,94 degrees, no alarm. So the starboard side top is still the hottest like last week before I replaced the thermostats and poppet valve. I have no idea what the thermostats are set for but the temp difference does concern me. BTW, impeller and housing replaced 10 months ago with maybe 10 hours logged since. I am using a round, single side water inlet muff. Any ideas?

 

[Capt Ken]

Re: Yamaha 150 ETD overheat warning buzzer on muffs

The upper starboard head will be the warmest since its the last to get water in the grand scheme of water flow. Especially at idle when water flow is the least.

 

[proftomda]

Re: Yamaha 150 ETD overheat warning buzzer on muffs

Thanks for reply Capt Ken. So its normal for the starboard side to run a bit hotter?

In researching, I hear much about the muffs being insufficient for anything above idle, rectangular vs round muffs for Yamaha, which side to have the water hose inlet on. I wonder, since water access 2 hours away, if I should use a trash can filled with water vs the ear muffs???... I also hear about scale build up in the water passages but how to tell???