Engine Temperature

[biltong]

I have a recently over-hauled 50HP Perkins 4108 in my yacht and would like to know if anyone out there knows at what temperature it should run at.

[SkiprJohn]

If I remember right my Perkins 4-107 was at its best between 140 and 160 F. I hope others with a more current memory or a 4-108 will respond.
kind regards,

[GordMay]

Generally speaking, an “open” raw or sea water cooled (salt) diesel engine should operate at about 140 → 160 degrees F; whereas a “closed” freshwater cooled diesel engine (/w heat exchanger) should operate at between about 180 → 190 degrees F.

[btrayfors]

Yes, that's right. The cooler temps with raw water cooling are specified in order to prevent salt precipitation in the engine's cooling passages, but diesel engines run more efficiently at higher temps (180-190F) as with closed cooling systems.

The 4-108, by the way, in the real world is way overrated in terms of HP. Although you see 50HP or 47HP or 42HP in writing, in reality it's a small engine which should be rated in the low 30's, IMHO.

I've lived with mine for 20+ years and love it. Just don't expect a lot of HP from it.

Bill

[biltong]

Thanks John, Gord and Bill. Seems all is well with the 4.108. Running as she should. Always good having confirmation.

[biltong]

Thanks all. It therefore seems that all is well with the 4-108.

[billwa]

Thought I would revive this thread as I have the same question on the same motor. Am working my way through issues with my engine and operating temp is next.

I have a digital pistol type thermometer. Where is the best place to measure the engine temperature - or does it not matter?

I suspect my engine has way too much cooling capacity, and is not reaching a good operating temp.

[Astrid]

I have never used one before, but I suppose the best spot to try would be the cooling water discharge between the engine and the heat exchanger.

[pjop]

Astrid's theoretical placement of the laser is correct, in my opinion. While far from a mechanic, I have a 4108 and had temperature problems a while back and I took my readings in several spots but primarily the fresh water pump housing. The highest reading were obtainable there, where water is coming directly out of the engine block.