Keel Cooled, dry exhaust electronic engine question
Dear List,
Need help please. If one is to power a 50' full displacement steel
trawler that has a displacement of about 72000 pounds with a single
engine, I understand that the rule of thumb is 2-3 HP per 1000 pounds.
The John Deere L1066T is the only keel cooled engine Deere offers. It
comes in 3 HP sizes, 135 continuous duty, 165 medium duty, and 170
high output.
Is Medium Duty equivalent "M2" rating?
Is that "good enough" if one wants to cross the atlantic on its own
bottom or should one be looking for a M1 engine rated for 150-200 hp.
I have asked these questions to John deere directly, with a less than
forthcoming response
So, if there is another keel cooled, electronic engine that should be
considered, could someone point it out to me? I could really use the
help.
TIA
Lee Licata
"...So, if there is another keel cooled, electronic engine that should be
considered, could someone point it out to me? I could really use the
help...."
You may want to contact Lugger (http://www.northern-lights.com )
They make "marinized" versions of John Deere engines. Their engines are used
in several brands of trawlers, including Nordhavns.
Just to get a sense of what engine an equivalent Nordhavn would have, I
looked at their spec sheets. An 85,000 pound Nordhavn 47 comes stock with a
Lugger L1066T.2, which is rated at 173hp (at 2,400 rpm). I would think you
want what they call their "Continuous Duty" engine.
You may get the best information by surfing trawler sites looking to see
what engine is in comparably sized, and weight, trawlers.
-Ken Williams
Sans Souci, Nordhavn68.com
John Deere sells a lot of L6081AFM engines for installation in keel-
cooled, dry exhaust Nordhavns. It's an 8 liter engine with 330 hp. My
boat (N55) has plenty of power for its loaded weight of 125,000
pounds. Engine is electronically controlled and burns very clean.
Two boats with this engine crossed the Atlantic this year... its an M3
rated motor, which basically says you can only run at full power for 8
hours out of 24 hours. In reality, you are rarely above 30-40% power
on a passage.
It's a fair bit less expensive than the Lugger engine, a 12.5 liter
monster, that puts out 340 hp, but at an M1 rating. Both engines fit
the 2-3 hp per 1000 pound criteria.
I don't see any sense in putting a monster M1 rated engine on a long-
distance passagemaker (which enables continuous full power operation
that burns 18 gallons an hour) when you really need to burn only 3 or
4 gallons an hour or less to make it across the pond. Either buy a
small engine and run it hard (and give up reserve power), or buy an M2
or M3 rated engine of moderate displacement that can give you high HP
for crisis events, but will run efficiently at low power and low fuel
burn for the usual long periods of cruising.
Anyway... my opinion.
John Marshall
Serendipity - N55-20
On Feb 8, 2008, at 1:14 PM, LA Licata wrote:
Dear List,
Need help please. If one is to power a 50' full displacement steel
trawler that has a displacement of about 72000 pounds with a single
engine, I understand that the rule of thumb is 2-3 HP per 1000 pounds.
The John Deere L1066T is the only keel cooled engine Deere offers. It
comes in 3 HP sizes, 135 continuous duty, 165 medium duty, and 170
high output.
Is Medium Duty equivalent "M2" rating?
Is that "good enough" if one wants to cross the atlantic on its own
bottom or should one be looking for a M1 engine rated for 150-200 hp.
I have asked these questions to John deere directly, with a less than
forthcoming response
So, if there is another keel cooled, electronic engine that should be
considered, could someone point it out to me? I could really use the
help.
TIA
Lee Licata
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Passagemaking Under Power a
Hi, I have been repowering this winter and struggling with the engineering, I had simular experiences with Deere Corporate engineering. From a fundemental perspective displacement boats require x power to do hull speed, then the propeller appature can only be fitted with a prop diameter that is within 10% of that space, a 34 inch prop requiring 3.4 inches of clearance for example. That prop, whatever size has a tip speed that should not be exceeded-and usually should be limited to 400-500rpm to achieve hull speed without cavitation--that also requires x power. Knowing these x power requirments will help you pick the right engine, Gerrs Propeller Handbook would be that reference.
Every engine has a torque peak, which usually is where the best fuel economy is achieved.
with the Deere engine I chose 1200-1400rpm is the torque peak and fuel use is sub 1 gal per hour, That represents 50HP or about 45 shaft HP, my 43ft waterline and 45,000 pounds requires 28Hp to achieve hull speed., 17HP is adaquate "reserve".
The Deere engine I am using is rated at 80HP/2500rpm/and 180ft pounds torque/4.5 gal per hour at those speeds. I have chosen to operate it at 12-1400rpm/220ft pounds of torque. 50HP/1 gal per hour-getting the gear reduction right to turn 400-500 prop rpm-and the size of the prop right to fit in the appature is key.
So my best advice is to pick an engine relative to prop size, gear the prop correctly, figure your hull power needs-then match the engine to those requirments, it will take less than you think-most boats are overpowered . A big prop moving slowly is the most efficient
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