Underloading

Thank's Rick.

Do you really own a CHB? What does she look like?

manyboats said:

Any idea why my engine is so stable coolant temp wise?

Click to expand...

You mentioned that the coolant temp rises to 190 and stays there. Mine rises to 192 and stays there because the thermostat is wide open and won't cool any farther. (So says the Cummins people) At first this alarmed me but the specs allow the temp to go to 203 safely. They also said that the newer diesels (most..not all) run hotter to achieve a more complete burn. ( I know other people that have the same model engine that I have and theirs run at 180.) So it's tough to sort out the BS from fact.

manyboats said:

Do you really own a CHB? What does she look like?

Click to expand...

Yeah, a 48. It is the second one after a 34 that I had in Seattle. It looks like every other CHB, a generic Taiwanese "trawler" style boat with soft decks and attractive interior woodwork.

It is on the Eastern Shore of Maryland where the chief mate and I have been "working on it" for the past few years and use it for a waterfront retreat when we need to escape from Florida. We were liveaboards in Seattle on my 65' wooden tug conversion for years before moving to MD to teach marine engineering. We bought it for a liveaboard but didn't bring it down here when I took this position because moorage here costs more than the boat is worth.

SeaHorse II said:

You mentioned that the coolant temp rises to 190 and stays there. Mine rises to 192 and stays there because the thermostat is wide open and won't cool any farther. (So says the Cummins people) At first this alarmed me but the specs allow the temp to go to 203 safely. They also said that the newer diesels (most..not all) run hotter to achieve a more complete burn. ( I know other people that have the same model engine that I have and theirs run at 180.) So it's tough to sort out the BS from fact.

Click to expand...

I don't think there is much BS involved. When the t-stat is wide open at a given rpm you have as much flow as you can get and the rate of heat transfer is limited by the area of the heat exchanger and the delta-T of the seawater and coolant.

If MB ran in high sea temps his max temp might be higher if it is already wide open. Or his T-stat might open more and maintain the same temp ... up to some as yet unknown sea temperature.

Probably few boats, even with the same engines, achieve the same flow rates and heat transfer capacity as another make or model or even the same. A few degrees either way falls into the noise level.

"They also said that the newer diesels (most..not all) run hotter to achieve a more complete burn."

IF a good cleaning/flushing of the system doesn't work ,,either a larger heat exchanger or a different coolant is called for.

Easier than locating/installing an oversized water pump,

Look up Evans Coolant if higher temperatures are normal.