Re: TWL: RE: Sizing a trawler diesel.
On Sat, 7 Apr 2001 12:10:41 EDT AlorMaria@aol.com writes:
Since we use our vessels purely for
pleasure, it is
doubtful that the engines will ever see the action they were
designed to
withstand. Any manufacturer who sells engines to the recreational
trawler
market should realize that.
On Sat, 7 Apr 2001 12:44:21 EDT Thataway@aol.com writes:
I have run Fords and Perkins for many thousands of hours at less
than 50%
of rated output, virtually never reaching 80% of output and I never
saw a
problem.
As Captain of their own ship, everyone is welcome to run their engine(s)
at any speed they feel is appropriate. However, everyone should be aware
of the implications of their actions. According to marine diesel
engineers, running a modern marine diesel engine at less than recommended
RPM for long periods of time will eventually do long term damage to your
engine. If you feel that this advice is not appropriate for your use, it
is your choice.
Marine diesel manufacturers and boat builders want to foster long term
customer satisfaction. It is important that vendors advise customers of
the best practice for use and maintenance of a product to achieve long
term satisfaction - even if the product is out of warranty. If a
customer wishes to ignore that advice, they have every right to do so. I
just don't think that ignoring suggested good practice is a good idea.
But you have the right to disagree and what that implies, that you are
assuming responsibility.
Patrick Gerety
Willard Marine
mailto:trawlers@willardmarine.com
http://www.willardmarine.com
You are correct, of course, Patrick. What I and others were trying to do
was to put it into perspective. If I can get 50,000 hours between overhauls
under ideal conditions, but only 10,000 hours under less than idea
conditions; then do I really care if I'm a typical recreational boater who
will never put 10,000 hours on my boat in the first place? Even as a
commercial operator, I still don't really care. I'm going to run the
engines in whatever manner is expedient for me, and then I'm not going to
have to worry about maybe having to do the occasional overhaul every several
years.
This business about running an engine at 70 percent of the rated power
level, or whatever similar number someone may care to quote, really has no
meaning when the same engine may be rated by the manufacturer at 120 or at
450 hp, depending upon how you might want to use it. The rating for
recreational marine engines is almost always at the top end of this range,
whereas the rating for commercial marine engines is at the bottom of it. I
might be running that engine at 90 hp as a commercial operator, and you
might be running the same engine at 340 hp as a recreational operator. We
are both running the same engine at 75 percent of its rated power level.
Now suppose you decide to run it at only 90 hp. Are you at 20 percent or at
75 percent of the engine's rating?
As a practical example, I have a friend with a 90 foot SWATH that he uses
for trans-oceanic charters. If he has a paying customer on board that wants
to go fast, he will run his engines at full rated power, which is 5000 hp
for the two of them. On the other hand, he has crossed oceans many times
putting only about a 400 hp combined load on both engines. The difference
is the difference between nine knots and thirty knots. Both his engines are
still basically new at about 20,000 hours. He needs the big engines because
sometimes he needs to go fast in order to earn a living; but he prefers to
save fuel when he does not need to go fast. He is not abusing these
engines.
Paul Kruse
paulkruse@cfl.rr.com
-----Original Message-----
From: owner-trawler-world-list@samurai.com
[mailto:owner-trawler-world-list@samurai.com]On Behalf Of pgslo@juno.com
Sent: Saturday, April 07, 2001 2:05 PM
To: trawler-world-list@samurai.com
Subject: Re: TWL: RE: Sizing a trawler diesel.
As Captain of their own ship, everyone is welcome to run their engine(s)
at any speed they feel is appropriate. However, everyone should be aware
of the implications of their actions. According to marine diesel
engineers, running a modern marine diesel engine at less than recommended
RPM for long periods of time will eventually do long term damage to your
engine. If you feel that this advice is not appropriate for your use, it
is your choice.
Marine diesel manufacturers and boat builders want to foster long term
customer satisfaction. It is important that vendors advise customers of
the best practice for use and maintenance of a product to achieve long
term satisfaction - even if the product is out of warranty. If a
customer wishes to ignore that advice, they have every right to do so. I
just don't think that ignoring suggested good practice is a good idea.
But you have the right to disagree and what that implies, that you are
assuming responsibility.
Patrick Gerety
Willard Marine
mailto:trawlers@willardmarine.com
http://www.willardmarine.com
Just got a new laptop computer. Does anyone know of a chart program for the Sea
of Cortez? Looked through the West Marine catalog and did not see one.
Norm Clark
Nova 40 Europa
San Carlos, Sonora, Mexico
Michael Kasten pointed out a simple solution to this problem. First the problem
isn't running the engine at low speed, but running at low power levels. In the
case of fix pitch propellers the two are synonymous. However, Michael pointed
out that the controllable pitch propeller (CPP) allows you to adjust the pitch
of the propeller to fully load the engine at the desired or required speed.
This allows you to run the engine at low RPM but optimum power for that speed.
This increases engine life and maximizes fuel economy.
Check out Michael's CPP web page at http://www.kastenmarine.com/articles.htm
Best regards;
Mike Schooley
At 08:49 PM 4/10/01 -0800, you wrote:
Michael Kasten pointed out a simple solution to this problem. First the
problem
isn't running the engine at low speed, but running at low power levels. In
the
case of fix pitch propellers the two are synonymous. However, Michael pointed
out that the controllable pitch propeller (CPP) allows you to adjust the
pitch
of the propeller to fully load the engine at the desired or required speed.
This allows you to run the engine at low RPM but optimum power for that
speed.
This increases engine life and maximizes fuel economy.
---=======================
According to every thing I've learned this is not true.
If you fully load an engine at cruising rpm you would void the warranty on
the engine by not letting the engine come up to it's rated RPM. The extreme
heat and pressures developed in the engine would'nt be acceptable. If this
was true we would all increase our propeller size to top out at our
cruising RPM. Methinks they would also call you SMOKEY.
What say all?????
.
Captain Al Pilvinis
"M/V Driftwood"--Prairie 47
2630 N.E. 41st Street
Lighthouse Point, Fl 33064-8064
Voice 954-941-2556 Fax 954 788-2666
Email yourcaptain@earthlink.net
Website http://home.earthlink.net/~yourcaptain
If you fully load an engine at cruising rpm you would void the warranty on
the engine by not letting the engine come up to it's rated RPM. The extreme
heat and pressures developed in the engine would'nt be acceptable.
You're right Al. But there's one item that you're missing. Load on the
engine is measured by the exhaust temperature. A pyrometer is installed in
the exhaust manifold or stack and you determine the level of load based on
that temp. If the temp gets too high you either back off the pitch or back
off the throttle.
Bob Deering
Juneau Alaska
Cummins will not let me load the engine in that fashion no matter what the
temperatures are.
.
Captain Al Pilvinis
"M/V Driftwood"--Prairie 47
2630 N.E. 41st Street
Lighthouse Point, Fl 33064-8064
Voice 954-941-2556 Fax 954 788-2666
Email yourcaptain@earthlink.net
Website http://home.earthlink.net/~yourcaptain