What is normal engine temp?

[John T1594]

I need a reality check. For the first time in almost twenty years of boating, I finally have an engine temperature gauge on my boat and I now stare at it continuously when the engine is running. Last fall, I installed a CruzPro T30 digital temperature gauge with alarm on my 2000 H340 with the Yanmar 3GM30F engine. In the slip at idle, it reads around 150-155 F. Running out of the marina at 2,000 rpm it reaches 160-165 F. Out on the bay at my usual cruising speed of 6.5 – 7 knots at 2,800 – 3,000 rpm it reads 175-180 F and I get a small amount of white steam from the exhaust. I have only once had the rpm’s briefly over 3,100 and backed off before the temp reached 190 F. I have the high temp alarm set at 190 F and I am sure I could get it to trip at the max rpm level for this engine (3,600 rpm). The original Yanmar alarm was set to go off at about 200 F. I have about 240 hours on this engine and am running a 3 blade, 15 X 9 Campbell Sailor prop. The raw water impeller is changed every other year and the coolant was changed two years ago. As far as I can tell, these are probably close to normal temps for this engine but I would like to hear from other 3GM30F owners as to their experience.

 

[Fred]

Thermostat temp?

Sounds normal.Most engines come with a 180 or 190 degree thermostat. It sounds like you have a 190 degree. Car and truck engines are almost all 190 degrees.Run your engine up to 190 and see if it stabilizes there or continues up. You should see the temp guage go down slightly as the thermostat opens, then go up a bit when it closes, then down a bit etc.If it gets to 195, slow down and check your cooling system.If that sounds too crazy, remove your thermostat and test it in a pot of water on the stove. It should open well before the water boils. Wash the pot really well before you use it for food.While you have the thermostat out, put the hoses back together and see if the engine will heat up to 180 even 150. What temperature is best for the engine will spark endless discussion and opinion. If your engine is in salt water and salt water cooled, lower temp is a good idea.Hotter makes the engine run more effeciently. Hotter also makes salt water chemicals stick to the exhaust manifold, and, in a raw water cooled engine, the whole cooling system.It's a balance between hot enough to run well and not so hot that it clogs up.

 

[abe]

Something wrong......

I have a H36 with a Yanmar 3GM30F and can run it at max rpm 3800 for an hour or so and temp will stay at 165 with no steam. I think that you are not getting enough raw water through the system. Check the elbow maybe its clogged.You should be running cooler at 3100 rpm.abe

 

[Fred]

Abe, if you're running at 165,

either you have a low temp thermostat, or somebody took the thermostat out of your engine, which is pretty common. The engine may last longer at the lower temperature.

 

[Fred Ficarra]

I use the original 160* thermostat in my 3GM30F

When I rebuilt the engine I tested the thermostat on my stove with a thermometer. It was fully closed at 160 and fully open at 163. Works great. John, your engine runs too hot. Like abe said, some thing's wrong. A quick test of your inlet water cooling efficiency is to let the engine come up to cruising temp and speed. Then touch the raw water outlet nipple at the outlet of the heat exchanger. It should be COLD. If you feel even room temperature warmth, something is WRONG. You shouldn't see white steam puffs from the exhaust either. Again, like abe said, check the elbow first, then the inlet cap of the exchanger. Look for calcification. Clean it with a long 1/4" drill. Of course if crud is blocking inlet flow you'll know it. Also realize that only 1/3rd of the heat exchanger tubes are used from the pump. The cap gaskets are arraigned in such a way as to cause the water to flow back and forth. It's more efficient. Oh, you do have an external strainer on your thru-hull, don't you. Mine came with no strainer at all. The factory put a Perko strainer inside the boat but by the time the weeds reached it, the 1/2" thru-hull was blocked.There you go. That's all you need to know to have a perfect 3GM30F cooling system. What's that? I missed something?