R-21 2GM20F Operating Temperature

[Bob Pisani]

I have a 1997R-21 with the 2GM20F Yanmar engine. What should the operating temp be? I'm showing about 182 degrees at 2700 rpm. What is a little strange is that I recently replaced all the hoses and before that the temp was about 178-179. A very slight difference but doesn't make sense, etc.

 

[SlackwaterJack]

The water the boat's in may be a couple degrees warmer
The new hose inside diameters are probably a tiny bit smaller than the heat/pressure distorted old ones.
An under 2% variance isn't unheard of for a water temp guage.

Wouldn't 182 deg. be just opening the thermostat?

 

[Bob Pisani]

Yes, you make a good point about the new hoses possibly being a bit smaller. As far as at what temp the thermostat should be opening I have no idea and am trying to find out. The 2GM20 Manual I have states the operating temp should be 178 at the top end ---- seems low to me but there is no thermomostat operating info. My guess is that no engine damage is occurring at 182, in fact it has never run better and the 110 remains constant if I'm alone on board or if I'm carrying 6 people and all their gear. Thanks for your reply--I'll dig deeper into this.