Bruce in Alaska wrote:

Bernie, ever wonder how all those diesel engines, at Truck Stops,
Idle all night long in cold weather, and still are able to pull BIG
Loads, the next morning, day in and day out, and still have 40K hours
between InFrame Rebuilds?

You can't compare truck engines and boat engines. As is often pointed out,
there are no downhills at sea. Truck and automotive duty is relatively
light compared to a marine engine which is essentially always going up hill.
The truck engine will frequently reach full power for short periods and get
nice and toasty. Then it coasts without cooling off a lot. This is very
different than marine duty cycle.

An occasional all night idle is a very small part of a trucks total
operating time. If a diesel is sized such that the boat can almost never
use the full power, it will never get up to the proper operating range. If
the prop is too small, as is often the case with yachts, even a headwind
that nearly stops the boat may not get the engine into the proper range.
You are never going to noticably compromise your properly sized diesel by
running it lightly when necessary. If it is too big for the boat or you
always baby it, you may have early problems.

We go through this a lot in sizing generator engines. It's nice to have one
that will handle the peak loads but, if there is a big spread between that
peak and normal operation, generator time to overhaul may suffer.

You are right though that newer governors are improving the situation. The
new electronically controlled engines can run at light loads for much longer
periods; maybe forever. There are still alot of diesel engines out there
(like mine) with governors that a pre WWII mechanic would have felt right at
home with.

--
Roger Long

In article ,
"Roger Long" wrote:

If a diesel is sized such that the boat can almost never
use the full power, it will never get up to the proper operating range. If
the prop is too small, as is often the case with yachts, even a headwind
that nearly stops the boat may not get the engine into the proper range.

If you knew ANYthing about modern Diesel Engineering, you would KNOW,
that diesels get up to "Operating Tempratures" at loads of between
5 and 10%, and then the Cooling System dumps the rest of the BTU's into
the outside world, as required to maintain the engine at "Operating
Tempretures". This is why they all have Thermostats in the Primary
Cooling Loop, which maintain the engine at Operating Temprature. The
Thermostat allows engine generated heat to recirculate, UNTILL the engine
comes up to Operating Temprature. If the Cooling System is designed
correctly, this equalibrium can be achived with the engine turning
with no, or a very small load.

Bruce in alaska
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