Fuel Usage--Ford Lehman 120

We have completed the first half of our summer cruise* from La Conner to* SE Alaska.
Here are some numbers re fuel consumption, engine hours, and speeds.

Total Miles traveled---792
Engine Hours---139
* (Includes idle/warm up, anchoring, and pulling anchor.
Gallons used---255 USG
Gallons per hour---1.83
Average speed in knots per engine hour---5.7
Nautical miles per US gallon---3.1

Fuel cost after refueling in Ketchikan, AK---$4.40/gal* (Includes some Canadian fuel).

Boat--Puget Trawler 37, semi-displacement, 25,000lbs, new bottom paint & prop tune--4-2011
Engine---Single Ford Lehman 120HP
Normal operating speed---6.5 to 7.0 knots 1600 to 1800 RPM (approx)

Larry H



-- Edited by Larry H on Sunday 24th of July 2011 02:24:52 PM


-- Edited by Larry H on Tuesday 26th of July 2011 11:49:21 PM

Thanks Larry for the useful info.
That is about the size and HP I am looking for in a trawler.
Nice record keeping.

-Puget Trawler 37, semi-displacement, 25,000lbs,

By rule of thumb, sq rt of LWL is under 6 ,times 1.15 so the speed is about 6,9K still water is about right .

25,000 divided by 2240 is 11 tons times 2,5 or 3 hp per ton is 27,5 to 33 hp required max .

33 hp divided by 18( optomistic HP per gallon) is 1.833 ,, 27 divided by a more realistic 15 (hp/gal) is the same.


so simple Rules of thumb can get one an idea of what the performance would be.

The best my 120 gets on my 34' mt is 2.3gph Now I am wondering if my injectors need serviceing

Probably not, I suspect it is just you are traveling at nearer the full hull speed in your 34 footer more of the time, (ie 1.34 x sq root waterline length in feet, = ~ 7kn), whereas Larry's 37 footer was dawdling along at below full hull speed (ie 1.15 x above = ~ 6.5kn, as FF calc'd), most of the time, with a significant fuel saving. Getting that extra knot of hull speed does add quite a bit to fuel consumption, and that's before you start semi-planing.

peteb
thanks Yes there is little difference in speed from a cruise rpm of 1650 to max of 2150 I have put over 1500hrs on my old 120 and have had burn rate vary from 2.7 to 2.2gph I guess water conditions and current

My 120 Lehman *is closer to 1.5/1.75 gal per hour at 1700/1750 rpm


-- Edited by jleonard on Monday 25th of July 2011 09:19:25 AM

Larry H wrote:
Gallons used---255 USG
-- Edited by Larry H on Sunday 24th of July 2011 02:24:52 PM

Click to expand...

You're doing the trip in the wrong boat * Good friends of our spent five months four years ago cruising from Bellingham, WA*to SE Alaska and back.* They went as far north as Juneau and spent lots of time meandering around in SE.* Total gallons of fuel used for the entire trip- 185.** Cruise speed was 6 knots.

The boat was a 30' Newport sloop.* And before you say, "well, they were able to sail," they put the sails up exactly one time for a few hours on one day of that five months.* The rest of the time they were under power.

But seriously that's impressive fuel economy that you've been getting.* Our GB (twin FL120s) burns 5-6 gph for a cruise speed of 8 knots.


-- Edited by Marin on Tuesday 26th of July 2011 06:33:18 PM

But it was a 30 foot sailboat! I, at least, have room to swing a cat, (and bring half of the house with me) (Admirals demand. LOL) I sure envy those sailboaters getting to stand out in the sun and rain and wear all that cool fowl weather gear, not!!

This years fuel economy is better than last years. The only difference is a new bottom job and prop service this spring.

Larry H

I sure envy those sailboaters getting to stand out in the sun and rain and wear all that cool fowl weather gear, not!!

Thats why they invented motorsailors.

Today a true 90/90 can be had,

90% the ability of a "pure" sailboat sans engine performance,

90% of the displacement offshore power boat distance and comfort .

Biggest hassle is there as expensive as any offshore boat , about 300% more than a coastal crawler ,
and are more modest in interior room until they get to about 60 ft.

If your galley or head needs to Echo, probably not for you!

Larry H wrote:
But it was a 30 foot sailboat! ....I sure envy those sailboaters getting to stand out in the sun and rain and wear all that cool fowl weather gear, not!!

Click to expand...

You'll get no argument from me on that regard.* While I really like sailboats and have crewed on them in Hawaii and here, the main reason we bought a powerboat is that we've spent all this time flying the PNW islands, BC, the Inside Passage, and SE Alaska looking down on all the boats and virtually all the sailboats are under power.* So our reasoning was that if we're going to be motoring along anyway we'd rather sit in a cabin with big windows so we can see everything (one of the main reasons we got a boat in the first place) rather than either being down in a hole with small windows or in an exposed or semi-exposed cockpit.

BUT.....* the economy of a sailboat allows one to take trips that might not be affordable in a power cruiser.* For example the couple with the Newport are retired on a relatively fixed income that is not huge.* Being able to go to SE Alaska on a five month cruise and burn only 185 gallons was a not-insignificant factor in their decision to do the trip.

But the most impressive thing to me is that this couple with their old sailboat actually made the trip. And made it successfully with no real problems to speak of.* As opposed to most boaters up here who talk big about going to Desolation Sound or the Broughtons or up the passage to SE Alaska but never do it.* So points to this couple (and you) for actually doing what they said they were going to do.

We've taken several cruises with this couple and their boat "La Mouette" ("The Gull").* I took the photo below as we were running from Rebecca Spit to Comox on the Strait of Georgia.* It was one of just two times on the three week cruise that the wind, the current, and the direction we wanted to go all lined up the right way for them so they could use the sails instead of the motor.* But I would have to say that, given the choice between cruising up the Passage to SE Alaska and back in a sailboat like this or not doing it at all, I'll be more than happy to take the sailboat, wind or no wind







-- Edited by Marin on Wednesday 27th of July 2011 12:28:11 PM

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-- Edited by JohnP on Wednesday 27th of July 2011 06:09:22 PM


-- Edited by JohnP on Tuesday 9th of August 2011 04:38:15 PM

Just adding my $0.02 to this discussion:


Boat - Grand Banks 36 Classic
Engines - Lehman 120's with ~ 1600 hours each and a very recent service


I recently installed all new Raymarine electronics and had both engines' cooling systems completely cleaned up, installed all new hoses, engine and transmission oil coolers, etc. I've owned this boat for a little over a year and the previous owner(s) had not logged any fuel consumption tests, so I decided it was time to find out how efficient the Lehmans really are. I filled the tanks, took the boat out on two trips in a single day - primarily to do an electronics checkout and to make sure that my autopilot worked correctly - and put 6.8 hours on the engines. Average speed cruising was 8 knots at about 1600 RPM - the Lehmans are very comfortable at that speed, and that's just about hull speed for this boat. Then I filled her back up with fuel and she took on 19.55 gallons.



So - by my calculations that's 2.85 gallons per hour. Not too bad for twin engines.

Popey,
The FL’s burn about 6gph wide open per engine. So your max fuel burn is basically 12gph.
You’re down almost 1000rpm so it’s not surprising you burned little fuel.
Marin Fare in the old post above ran his FL’s at about 50% load and burned 3gph on each engine. That was after he reduced his propeller pitch to get his prop load right. Too long ago to remember his rpm and speed.

We have twin Lehman 120s in our DeFever 44. At 1,650 RPM the boat goes about 7.3 knots (8.5 MPH) using 3.5 GPH. The boat weighs 56,000 pounds so I think this burn rate is pretty good for this boat. When assessing burn rates one must consider the amòunt of weight being moved through the water.

PopeyeGB36 said:

Just adding my $0.02 to this discussion:


Boat - Grand Banks 36 Classic
Engines - Lehman 120's with ~ 1600 hours each and a very recent service


I recently installed all new Raymarine electronics and had both engines' cooling systems completely cleaned up, installed all new hoses, engine and transmission oil coolers, etc. I've owned this boat for a little over a year and the previous owner(s) had not logged any fuel consumption tests, so I decided it was time to find out how efficient the Lehmans really are. I filled the tanks, took the boat out on two trips in a single day - primarily to do an electronics checkout and to make sure that my autopilot worked correctly - and put 6.8 hours on the engines. Average speed cruising was 8 knots at about 1600 RPM - the Lehmans are very comfortable at that speed, and that's just about hull speed for this boat. Then I filled her back up with fuel and she took on 19.55 gallons.



So - by my calculations that's 2.85 gallons per hour. Not too bad for twin engines.

Click to expand...

Sandpiper is 40', LWL 36, 40,000 lbs, single Lehman 120, displacement hull.

Burns 1.84 gal/hr @ 1700 rpm, 8 knots. Average of both directions, on a measured mile, near slack. Fuel consumption measured with a calibrated auxilary fuel tank. Speed with stop watch and GPS.

Larry H said:

I sure envy those sailboaters getting to stand out in the sun and rain and wear all that cool fowl weather gear, not!!
Larry H

Click to expand...

I spent several years cruising & living comfortably on a 35' Fantasia sailboat. Not sure I ever put on my foul weather gear. I do, however, remember on one leg from Roatan to Key West having to stick out my legs from the covered cockpit to refresh my fading tan. Note that a well designed sailboat can be both comfortable & store plenty. I not only had a lovely aft cabin, but a roomy standing workshop with bench. I've perused a lot of motoryachts up to 52' recently in search of our next purchase, & haven't seen a single one with such an amenity.

Hi guys, I'm new here. I'm looking at buying a boat that has two ford 363 cu.in. diesel that the tag say 108 hp. They're not Lehman but I guess the same base ford engine. SENATOR by Lunenburg foundry. The were installed in place of the 2 454 cruisaders.

The boat is a 40' Egg Harbor. I'm after a comfortable boat to use on rivers and canals and no need for speed but would like fuel economy. From what I've read here it look like a good choice.

Please give me your advice.

Thanks!

FF said:

I sure envy those sailboaters getting to stand out in the sun and rain and wear all that cool fowl weather gear, not!!

Thats why they invented motorsailors.

Today a true 90/90 can be had,

90% the ability of a "pure" sailboat sans engine performance,

90% of the displacement offshore power boat distance and comfort .

Biggest hassle is there as expensive as any offshore boat , about 300% more than a coastal crawler ,
and are more modest in interior room until they get to about 60 ft.

If your galley or head needs to Echo, probably not for you!

Click to expand...

I have the best of both. I carry a Hobie One 12 on my roof.

"The FL’s burn about 6gph wide open per engine. So your max fuel burn is basically 12gph."

True,,,, but FL are not heavy duty industrial engines , so the service life might be reduced by 3/4.

If one requires 120HP there are far better engine choices.For 2-3GPH they are great.

The FL’s were designed as a truck engine, I would consider that an industrial engine.

Almost identical to the figures my F.L. 120 gives me on a 36 foot Albin at about the same RPMs and Speed. An acquaintance with the same boat as mine told me he runs his at W.O.T., around 2500 RPM and doesn't notice much increased fuel burn or noise. Gets another 1 -2 mph. I don't believe him. ( of course he is the guy who removed his aft steps and built a stairway out of cement blocks on his cabin roof because Albin tend to float a bit "down in the bow" )

pete

FF said:

...True,,,, but FL are not heavy duty industrial engines , so the service life might be reduced by 3/4...

Click to expand...

In his course, I remember Bob Smith saying the FL120 WAS AN INDUSTRIAL ENGINE, designed to be run at near wide open, 24/7.

Jim

Designed versus successful service life are 2 different things.

There is a lot of anectdotal evidence the Lehman's prefer 1/3 to 1/2 their power output for reliability and longevity.

No facts .....just the last 8 years of running one and consuming every tidbit about them.

I run my 1980 Grand Banks 36 with twin diesels at 1500 RPM. Being a pilot, I know how to set up engines for range. I average 1.1 GPM per engine, so 2.2 GPH running at 7.8 kts. I have consistently average 2.2 GPH over 7 years of owing this boat.

Cheers.

120 fuel consumption

We have twin 120's in our 37 Uniflite Coastal Cruiser. Fuel con sumption is really close to 3.1 gph combined, at 8.5 knts, 1850 rpm.

KevinGB36 said:

I run my 1980 Grand Banks 36 with twin diesels at 1500 RPM. Being a pilot, I know how to set up engines for range. I average 1.1 GPM per engine, so 2.2 GPH running at 7.8 kts. I have consistently average 2.2 GPH over 7 years of owing this boat.

Cheers.

Click to expand...

Mischief said:

We have twin 120's in our 37 Uniflite Coastal Cruiser. Fuel con sumption is really close to 3.1 gph combined, at 8.5 knts, 1850 rpm.

Click to expand...

I was getting just under 10LPH ave. combined measured over several years.

Kevin, did you convert to US GAL? or CAN GAL. as 6.7L seems low but 8.4 close to my GB36

Mischief, 3.1 US gal is about 11L