Engine temperature

[kingofcary]

Dear All … I have a question on engine temperature while running. I’ve read conflicting information but I thought my M 35B universal running in my Catalina 350 would have an operating temperature of 159. What do people experience. At 2400 rpms I have been seeing hotter .. engine is 2007 with around 1500 hours.

[donradcliffe]

It depends. If the engine is raw water cooled, the temperature should be less than 160 deg F to keep salt crystals from forming. For a engine with a heat exchanger, the engine will be more efficient at 190 deg F. For an air cooled engine, the Mercedes diesel in my RV normally gets over 220 degrees F going up hills on hot days.

[Tetepare]

My m25xp in the Catalina 30 would run 160 up until seawater temp was about 65, above that it would run at 165 no matter what the sea temperature or RPM.

[Nicholson58]

There are various thermostats available. Also, thermostats can go bad. I test and mark all of mine. Hot water in a sauce pan on the stove. Use a digital thermometer. I keep both 160 and 180 thermostats. I found two bad spares this way.

[HeywoodJ]

This is from the M35B Technical Manual: