Yanmar Operating Temperature(2QM15)

[Ted]

What is the " normal" operating temperature for a 1980 Yanmar 2QM15? Historically, ran at 160-170 degrees.After replacing water pump, temp. gauge, sending unit and flushing entire engine; now operates at 140 degrees. Gauge and sending unit tested OK.

 

[Aldo Lozano]

Same here, Ted...

Although I have a 1GM, and of course is sea water cooled, I am reading around 130F at 1800/2100 rap, with load. Oil pressure about 40 psi and neither change on two hours trips.The temps and pressure are double checked with another instruments, but the engine don't ever get in the range - in my opinion, which should be for a diesel engine with a ligh load (around 160F) Thermostat was checked ousithe the engine and just in case, replaced with a new, also tested unit. Every marine mechanic(?) I asked, the first answer is "Yanmars don't have temp gauges", the second is "Be thankfull...You don't get so much corrossion that way" and "I don't know..." Does anybody?Aldoalozano@monmouth.com

 

[Henry Weber]

Yanmar engine temp

The fresh water cooled small Yanmars typically operate at a very low temperature (120F). Although this is not optimum for the diesel and combustion area, it is a trade-off because the parts in contact with the sea water being cooler will accumulate far less scale. My Yanmar YSB12 has a thermostat which opens at 115 degrees.The engines with heat exchangers on the other hand should operate much hotter -- around 180F is good.Henry

 

[Aldo Lozano]

Henry is right, Ted...

No only that... After I posted my answer to you, I went to the boat and start wading through the Yanmar manuals and, sure enough, buried in the middle of one there is the only reference to operating temps: 50 to 60 degrees centigrade (120/140F)...I ponder if the thermostat for the freshwater intercoolers will fit in the seawater cooled engines...Hummm...Again: anybody knows?Aldoalozano@monmouth.com

 

[Jim Logan]

2QM15's run cooler for a reason

raw sea water cooled engines run at cooler temperatures than closed cycle cooling systems because this limits scale formation in the engine cooling passages. If you put in the wrong thermostat and run at a hotter temperature, you won't notice anything at first, but your engine will build scale up much more rapidly in the cooling passages and will overheat, the only cure will be to then do an engine flush using harsh chemicals to dissolve the scale. Also, the elevated temperature of the sea water coolant will make corrosion much more of a problem with your cylinder liners and other parts of the cooling system. Yanmar makes different thermostats and coolant temperature sensors to use depending upon whether the engine is raw water cooled or closed cycle cooled. Best advice is to get the official Yanmar service manual for your exact year of engine and read it and follow directions. These engines will last for over 8000 hours without a rebuild if you don't do something dumb to them like listening to people who don't have the manual. The 2QM15's were built with a high nickel content block and associated parts to withstand the effects of sea water cooling, as long as you don't use the elevated temperatures of having the wrong thermostat.

 

[Howard]

Thanx

Sincerely appreciate your insight!!