I’m confused

[Scarlett]

From what I read here it seems that most people with 12-71 or 8-71 run 170 degree thermostats and there engines run at around 180 degrees at cruising RPM, yet I keep seeing Detroit’s that run at 160 degrees at cruise. I assume they are using lower temp thermostats. Which is best? I just surveyed a boat with 8-71TI engines and they ran at 160 with my gun at the same RPM my engines would be at 180

[luckydave215]

I have heard (more than once) to install colder thermostats in my engines because it will prevent overheating.
Which is, of course, a classic example of bogus revelation.

[Captain Ralph]

Although there are different temp settings for Detroit thermostats, most use the 180 degree units. I have 650HP-12V71TIs with 2 180 degree stats per head. At slow cruise, I read 140 to 150. At fast cruise we see 170 degrees.
In the pins (WOT), I may see 180 to 190.
Alarms go off at 215 to 225 (thankfully never been there).
This is testament that the cooling system is pretty good if not over sized on some models.

My thought is; Don't let the low readings confuse you. Just ensure the high readings are accounted for and under control.

[racclarkson@gmail.com]

From what I read here it seems that most people with 12-71 or 8-71 run 170 degree thermostats and there engines run at around 180 degrees at cruising RPM, yet I keep seeing Detroit’s that run at 160 degrees at cruise. I assume they are using lower temp thermostats. Which is best? I just surveyed a boat with 8-71TI engines and they ran at 160 with my gun at the same RPM my engines would be at 180

John, I have 160 stats and run about there anywhere from in-gear idle to about 1,000 RPM. At 1,800 or so, I run at about 180-185 F. That's also in 85-89 F seawater. I think if you run at hull speed predominantly hotter is better. But it can also be a thin window from 185 to uh oh.

Just freshwater flushed port motor leak checking after pump rebuild. Pretty good block heat with 97 F tap water!

[luckydave215]

On the west coast we typically run in 50-60 ish degree water, cold thermostats are a bad idea here.
Mine run at 171 port and 173 starboard regardless of load or speed.

[Captain Ralph]

I have heard (more than once) to install colder thermostats in my engines because it will prevent overheating.
Which is, of course, a classic example of bogus revelation.

Correct. Diesels are thermal engines to a point. For the oil to flow correctly, the coolant to work correctly, the block and gaskets to set correctly, the lungs and fuel to do their things correctly, the target water/block temperature should be around 180 degrees on a factory block.
This is usually where the block is when real horse power is oozzing off the propellers.

[SKYCHENEY]

An old timer Detroit mechanic that has worked on our equipment since the late 70's told me to only run 170's in marine applications. I have always done just that.

[Boatsb]

Where did you measure the the temperature? Its not consistent along the whole engine

[Scarlett]

I usually measure at the T-stat housings.