On Mar 22, 9:05 pm, " wrote:
... I'm planning on taking the boat out in the morning anyway,
so I'll try and pay particular attention to the motor and report some
symptoms for you. ...

Alright, I took the family out for a cruise yesterday and did keep an
eye on the engines. I reduced the warm up period to about 10 minutes
and the batteries were fully charged when I left the dock. On the run
out of the harbor I set both throttles to about 2300 and for the first
5 minutes or so the stb eng would run up to just under the desired rpm
and then drop off 200 fairly slowly and then run back up. The full
cycle taking about 10 seconds. We set sail and sailed for a couple of
hours and then restarted the motors to anchor and throttle response
appeared normal. After a couple hours at anchor I motored home (about
4 miles). The engines appeared to run normally. Neither smokes at
WOT and both ran up to full rpms (though we were running with a
strongish tail wind). I know this isn't going to help my case as it
sure sounds like air in the fuel. Still, I'm pretty convinced that's
not it. I have spent a lot of time with the fuel system. The filters
are new. The day tank is above the engine. There doesn't appear to
be any water or growth in the fuel. But, I hope everyone who wants to
will feel free to tell me what they think the problem is. Fire
away!

-- Tom

PS. And thanks.

wrote in message
...
On Mar 22, 9:05 pm, " wrote:
... I'm planning on taking the boat out in the morning anyway,
so I'll try and pay particular attention to the motor and report some
symptoms for you. ...

Alright, I took the family out for a cruise yesterday and did keep an
eye on the engines. I reduced the warm up period to about 10 minutes
snipped.

Warming up a diesel for 10 minutes is unnecessarily long and does no good.
Give them a couple of minutes to make sure everything is working and then
leave the dock and get some load on.
Prolonged idling from cold causes a lot of wear.

On Mar 24, 9:30 am, "Edgar" wrote:
Warming up a diesel for 10 minutes is unnecessarily long and does no good.
Give them a couple of minutes to make sure everything is working and then
leave the dock and get some load on.
Prolonged idling from cold causes a lot of wear.

Help me out, how does it cause wear? Sure, I don't know squat about
engines but it from book learning and a tiny bit of expericene:
Assuming that the oil is of a suitable weight it should work just fine
at idle. The manual requires racing the engine periodically if
running at low speeds for over 2 hours but requires not less than 5
minutes of warm up before _any_ load is applied. Letting the oil
splash about and passing it through the filter once or twice before
things get really hot seems like a good thing to me. The motor is a
bigish chunk of metal and gaskets and spings and such and heating it
up fast must cause stress. I've had the exhaust elbows off both
engines twice and there was no evidence of unusual coking. FWIW, I
generally push the idle speed up during the warm up and have some
alternator load so the motors aren't likely to be running way under
temp anyway.

-- Tom.

wrote in message
...
On Mar 24, 9:30 am, "Edgar" wrote:
Warming up a diesel for 10 minutes is unnecessarily long and does no
good.
Give them a couple of minutes to make sure everything is working and
then
leave the dock and get some load on.
Prolonged idling from cold causes a lot of wear.

Help me out, how does it cause wear? Sure, I don't know squat about
engines but it from book learning and a tiny bit of expericene:
Assuming that the oil is of a suitable weight it should work just fine
at idle. The manual requires racing the engine periodically if
running at low speeds for over 2 hours but requires not less than 5
minutes of warm up before _any_ load is applied. Letting the oil
splash about and passing it through the filter once or twice before
things get really hot seems like a good thing to me. The motor is a
bigish chunk of metal and gaskets and spings and such and heating it
up fast must cause stress. I've had the exhaust elbows off both
engines twice and there was no evidence of unusual coking. FWIW, I
generally push the idle speed up during the warm up and have some
alternator load so the motors aren't likely to be running way under
temp anyway.

-- Tom.

When the cylinder walls are cold acidic combustion products stay on the
cylinder wall instead of leaving as vapours with the exhaust gases and this
leads to increased wear. Maximum wear occurs near top dead centre when the
piston is slowing and reversing its motion because this is the area where
there is least oil film and the slow motion of the piston rings does not
prevent some metal to metal contact. Lower down the cylinder the piston
rings are riding on an oil film and wear is much lower.
Idling for 5 minutes is not as good for warming up the engine as getting
some load on within, say, 2 minutes. The bit about 'racing' the engine after
prolonged idling is to get some fuel through the injectors as the flow at
idling is so small that the fuel in the injector can start to polymerise and
clog the holes in the nozzle. Here again running at speed with some load on
is better than 'racing' the engine if by racing you mean running up to full
speed on no load.
I accept that your alternator will provide some load but whether this is
enough to be effective depends on the size of the alternator relative to the
power of the engine and whether the alternator finds a battery that is
already fully charged or one that is low and needs some charge.

On Mar 24, 12:19 pm, "Edgar" wrote:
When the cylinder walls are cold acidic combustion products stay on the
cylinder wall instead of leaving as vapours with the exhaust gases and this
leads to increased wear.

This I did not know.

Idling for 5 minutes is not as good for warming up the engine as getting
some load on within, say, 2 minutes.

The manual is pretty specific. I wonder if there is a trade off that
depends somewhat on the engine involved.

The bit about 'racing' the engine after
prolonged idling is to get some fuel through the injectors as the flow at
idling is so small that the fuel in the injector can start to polymerise and
clog the holes in the nozzle.

"This is done to clean out carbon from the cylinder and the fuel
injection valve." Is what they say and I think that means what you
said.

Thanks,

-- Tom.