On Fri, 5 Jan 2007 14:03:28 -0500, "Roger Long"
wrote:

I've never had the opportunity to see the inside of an abused diesel
cylinder at overhaul

I have a few pictures if you're interested. Basically they show scuff
marks on the cylinder liners and pistons from where the pistons
started to seize up. Probably the most expensive pictures I own. :-)

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

I feel your pain. Somewhere, I have a picture of the cam lobe missing .005
inches of its top that cost me and my airplane co-owners $25,000.

--
Roger Long

"Roger Long" wrote in news:459ea606$0$18859
:

I certainly see more black smoke coming
out of the exhausts of commercial boats than yachts.

Commercial boats get paid for WORKING, so maintenance goes undone until you
can't go WORKING any more. (An example is Charleston shrimp boats go
uncaulked until they're leaking so bad the pumps can't keep the water below
the intakes to go shrimping, their prime reason for being.)

Yachts get maintenance, most well before they actually need maintenance
because the owner has money and nothing to do with it. Ain't it grand?

Also, a fisherman headed out to be number one isn't interested in "sweet
spot cruising" to the fishing...(c;

Reasons for all the black soot shooting out the dry stacks welded up by
Uncle Henri are fairly obvious...(c;

"Roger Long" wrote in news:459ea606$0$18859
:

I've never had the opportunity to see the inside of an abused diesel
cylinder at overhaul

Has nothing to do with boats, but my 1973 Mercedes naturally-aspirated
2.2L 4-stroke 4-cylinder that spent the first 23 years of its life
driving across Charleston City traffic, owned by a retired Navy captain
and his wife, is probably a pretty good example of an abused diesel. 23
years is the point at which I did a 4-hole overhaul on it, somewhere in
the 330,000 mile area, but we're not sure how many times it went around
its 99999 mile odometer before I got it. The Captain couldn't honestly
remember when I bought it from him. It sat idling in the awful city
traffic most of its life before I got it....and since I overhauled it.

One cylinder was lower in compression than the others, so my mechanic,
Stephan Reinhardt, a German who worked at the main engine factory before
coming to the US to start his own Mercedes shop, Star Motor Service,
decided to pull it apart. One of the compression rings was cracked and
he made me a great price on doing a full overhaul, restoring the little
diesel to new condition. I was amazed how little carbon and deposits
were in the cylinders and in the pre-combustion chambers in the head
where the injector and glow plug reside. Every time I run it, I'm still
in awe that the explosion in the pre-combustion chamber flows down the
tiny hole through 5 little ports into the main cylinder without just
blowing it all to hell. You could see the trail of the explosions as
they came out into the cylinder along the head in a 5 pointed star
pattern. I still have a "souvenir piston" of the original 23-year-old
set Stephan presented me, leaving its original piston pin pressed into
one side of the piston, but sticking out so you can see the fine machine
work and quality. The pin has the polish of a fine precision mirror and
you CANNOT run your fingers across its surface and define where the
connecting rod bearing bore the brunt of the blast and moved back and
forth across its surface for 23 years of use. That pin is a true trophy.
The piston top is black, but shows no carbon buildup on it...even not
along the tracks made by the 5 holes blowing out sideways against it
during the "main bang" as it passed TDC...over and over.

The bearings in the bottom were "ok" but I wanted them all replaced.
Stephan started to put the old 23-year-old double-row overhead camshaft
roller chain back against its original tensioning shoe. I said "replace
it, it's old and has gotta be tired by now". Even the shoe, which was a
brown fiber material was just fine! 5 links from that chain were in the
"trophy box". Before his death in a terrible motorcycle accident, he
never let me live down replacing a perfectly good chain...(c;

It sits outside waiting to go any time you're ready. If we're going to
California, I'd like to take it by the shop for an oil change and filter
before we leave. It runs on 20W-50 Rotella T, just like the big boys
rigs. I bought it its 12th monster starting battery 3 weeks ago. Cranks
much easier when all the plates don't have holes in them....(c;

Stick your finger in its exhaust gook and you'll never get it to come
clean. It's always like a greasy lamp black....even before I started
running it on 80% old frying oil and 20% regular gas...which cranks fine
but it hasn't gotten cold in SC at all this year. By Summer, I hope to
be running it on 90/10 with even less thinning gas in it...in the heat.

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
--
add a 2 before @

Bruce in Alaska wrote:

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

Heat rejection to the cooling system isn't representative of localized
temperatures and a host of other factors in the combustion chamber that
cause problems at light loads. These problems are not all that serious but
they do somewhat offset the wear and tear benifits of running and engine too
lightly for very long periods.

Your properly sized diesel or generator is not likely to suffer from any
amount of light running that is dictated by operating conditions. However,
if it is significantly too large for the job so that it NEVER comes up into
it's intended operating range, you probably won't get more, and quite
possibly, less, service out of it than if was run normally.

--
Roger Long