Yanmar 6BY260 R29 2010

[Thomwa]

Is 212 degrees at sustained WOT within acceptable limits? Do I need to change thermostat or change impeller or stop worrying? Looking forward to your responses.

Also, What is a good optimum R.P.M. for continuous running to not be abusing or straining 6 Cylinder Yanmar in 2010 R-29?

 

[Shared Dream II]

I don't run extended periods at WOT. There is a placard on the engine that rates it for continuous operation at 3600 rpm. (might be 3650, I haven't looked in awhile). At this rpm, I run 207 degrees with a sea water temperature of 85 degrees. When I was on the west coast, it ran about 205 degrees.
Having said that, about a year ago I had noticed that my engine temp had steadily increased a degree per week. It took awhile to track down, but I finally located a leak in the coolant at the hose connection inside of the hot water heater. (the fluid wasn't visible from outside as it was being absorbed by the insulation and held in the pan). I'm not suggesting that you have the same issue, but I would start with ensuring that you have sufficient coolant. Checking the overflow bottle isn't enough. Before you start the engine, check the coolant at the engine ( radiator cap is located on the starboard side of the engine and is accessible with the cockpit engine cover in the open position.) If this checks out fine, then the other items to check are the seawater flow to the heat exchanger, the impeller, and the thermostat.
What temperature do you run at for 3500 to 3600 rpm?

 

[JerryE]

My engine temperature seemed high, compared to what the manual said and it wasn't until I was overheating with alarms going off that we discovered the optional heater hoses Yanmar supplies (to hook up to the boat's cabin heater) were leaking. Contacting Yanmar resulted in comments that the engine was running within specs (i.e., no alarms going off) even though it was high compared to the manual specs. Don't wait for a disaster.

The hoses in all but the very newest BY engines are 3.5mm thick and even a small leak at the pressures we run (our engines run just under boiling which generates high pressures in the cooling system) will become egregious. Check out the Attachments that Andrew has posted on the home page regarding the Yanmar recall. A tiny unnoticed leak can raise your temperature a few degrees, like it did mine–eventually, the hose will let go and wham you have alarms going off and real worries. Andrew has photos of the what the old 3.5mm and replacment 4.5mm hoses so you can tell what is in your boat.