Let's say you just took delivery of a used 27000# trawler powered by a
single Cummins turbo-diesel 220, model 6BT5.9M. You want to get maximum
miles per gallon out of it and know the slower you go, the better, but
these motors don't like to go slow for a number of reasons. Of course,
you also want it to last forever because it might cost $10,000 to
rebuild it, not including pulling it out and putting it back in..

What would you consider a minimum cruising speed, with an occasional
shot at 2000 rpm just to clean things out?

Capt. Jeff

Tamaroak wrote:
Let's say you just took delivery of a used 27000# trawler powered by a
single Cummins turbo-diesel 220, model 6BT5.9M. You want to get maximum
miles per gallon out of it and know the slower you go, the better, but
these motors don't like to go slow for a number of reasons. Of course,
you also want it to last forever because it might cost $10,000 to
rebuild it, not including pulling it out and putting it back in..

What would you consider a minimum cruising speed, with an occasional
shot at 2000 rpm just to clean things out?

Capt. Jeff



Be guided by Cummins & just ask them. The usual thing is over 1/2 -2/3
for continuous running. Long term light load continuous speed is not
good & after a while you'll stop giving it the regular bursts.

The negative effects can be overstated, there is a ferry around here
that even made it into the Cummins news magazine for it's number of
hours without overhaul, I've forgotten the exact number just now, but it
was well over 20000hrs with not much more than standard servicing & it
was in the situation you describe, lightly loaded, 0600-2300 X 365 days.
It was (is) run at reasonable high revs. They slip the ferry every 2-3
yrs & the intention was to re-engine every 3 years last I heard they had
left it there.

Again always ask Cummins & this para. is well against what Cummins will
say but.................. if you have a situation when you are
essentially overpowered, you can overprop if the usage is well managed
(i.e. the engine must never be run at a throttle setting where any extra
will not result in the engine easily increasing revs) This will give you
same boat speeds at lower engine revs & make the engine produce more
torque, it means you must operate it as a lower powered motor(i.e. you
don't have the option to give it full throttle even if the storm front
is coming). Again not ever recommended & especially not by Cummins. The
marine versions of some engines have a different governor on them so
excess torque can't be made below a related safe revs, but this is not
to be relied upon.

Funny story?? The liar Krause was carrying off the Cummins powered
lobster boat lie for months as it was being imaginary built, doing all
his online searching as he does, trying to make the lie plausible. As
always with liars he was exposed by the easy detail he had no clue about.

The imaginary boat was launched (I suspect a charter person he pays to
take him fishing it seems twice a year?? was having a boat built) & of
course I asked how the Cummins bloke enjoyed the ride?? Needless to say
he had no clue about what I was asking, even took it that I'd said there
was something wrong with the Cummins!!!:-)

Too funny; for big new Cummins engines like that it's a condition of the
warranty that one of their reps visits the boat & goes for a run, "just
to ensure everything is operating correctly" but in reality they do it
to make sure the boat is NOT overpropped, if it is they say so & tell
you the warranty will start when the correct prop is fitted. The
internet has given the lying idiots a new tool but being tools
themselves they still don't know anything.

K

Tamaroak wrote in news:Fd2dnbJAg-bp2pbZRVn-
:

these motors don't like to go slow for a number of reasons

Huh?? Where'd you hear this nonsense? A diesel doesn't like to go slow?

What reasons do you know about to go with this??

A friend, who should never have been allowed to drive a 56' Hatteras away
from the dock, ran its twin 8V92TA, twin turbocharged train engines at idle
for many years before I came along. I must admit there was a "little
carbon" in the waterboxes that came out when I "opened 'er up" offshore of
Charleston. It looked something like a ship blowing the boilers..(c;

These idled-for-years old Detroit Diesels had ONE little weak injector
spring in one engine when the diesel shop pulled them all apart for
inspection for the massive survey the buyer paid for when he sold it. ONE
spring! To start them, you simply flipped the switch to ON and barely
touched the start button and they jumped to life, even stone cold.

I don't believe Dan hurt them treating these beasts like the boat was a
trawler all those years he owned it.

Sure made a big cloud of carbon (cough)(cough)(choke)(gasp) 5 miles
offshore...(c; I told him I was trying to hide the brown trail he was
leaving when the mascerator pump was emptying those massive dirty tanks...
(c;

Tamaroak wrote

these motors don't like to go slow for a number of reasons

Larry wrote:

Huh?? Where'd you hear this nonsense? A diesel doesn't like to go slow?

What reasons do you know about to go with this??


Suggest you check out "wet stacking".

Usually requires and idle RPM around 1,400 RPM to prevent.

Lew

Have a search at www.boatdiesel.com, this has been covered many times.
There is also an article on this:
http://boatdiesel.com/Articles/Artic...ion.cfm&Y=2004

You will need to join the web site to read this one, ($25/yr, and
worth it every once and a while).

I to have a 6B in a trawler and have am OK with slow operation. My
normal cruise is 1400 rpm (6.7kn). Key here is to get the motor to
operating temperature (Idling, even at a fast idle will not do it, you
need to run the boat) and then make sure it stays at temp.

The 6B's at times have problems with their thermostats, so watch that
and if the temp falls off, then change it out 1st thing. I had to
change out mine at 400hrs, no problems after doing so.

When we run Christmas ships I spend a few hours at a time at 1100-1200
RPM, and the temp always stays up. So, again, the key here is get up
to temp (I usually run around 1700 or so to make sure I am up to temp)
and do not worry. Based on what I have seen from people who have been
around motors with high hours, I am expecting well over 10,000hrs on
my motor. Turbo included

-al-

On Sun, 05 Mar 2006 14:17:33 -0800, Tamaroak
wrote:

Let's say you just took delivery of a used 27000# trawler powered by a
single Cummins turbo-diesel 220, model 6BT5.9M. You want to get maximum
miles per gallon out of it and know the slower you go, the better, but
these motors don't like to go slow for a number of reasons. Of course,
you also want it to last forever because it might cost $10,000 to
rebuild it, not including pulling it out and putting it back in..

What would you consider a minimum cruising speed, with an occasional
shot at 2000 rpm just to clean things out?

Capt. Jeff

"Al Thomason" wrote in message
...

When we run Christmas ships I spend a few hours at a time at 1100-1200
RPM, and the temp always stays up.

Al, please excuse my ignorance,

What is a "Christmas" ship?

RCE