Fuel usage: "new" vs "old" diesel engines
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sunchaser
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We all (most of us anyway) have diesels in our boats and have anywhere from a little to a lot of data on the fuel burn of that specific engine. Without treading over already pretty well stated thoughts, I think Slow Goes It is very pleased with his engine, VP prop and vessel in general.
I can accept that proudness, remembering that between applying bsfc knowledge and a normally accepted 4 stroke diesel burn rate of 17.5 to 20.5 HP/GPH, engine parameters are in a tight envelope. It would seem that bragging rights for NMPG then come back to hull design, correct props and velocity selected. Witness a sailboat under power, gosh those high NMPG numbers can be stunning. The closest 60' + vessel I can think of that gives the sailing folks a run for their money is the FPB, with roots in Steve's fabulous Deerfoot S/V design.
I can accept that proudness, remembering that between applying bsfc knowledge and a normally accepted 4 stroke diesel burn rate of 17.5 to 20.5 HP/GPH, engine parameters are in a tight envelope. It would seem that bragging rights for NMPG then come back to hull design, correct props and velocity selected. Witness a sailboat under power, gosh those high NMPG numbers can be stunning. The closest 60' + vessel I can think of that gives the sailing folks a run for their money is the FPB, with roots in Steve's fabulous Deerfoot S/V design.
Slowgoesit: First-love your boat. I was on a similar looking Beebe boat in the San Juans. It had two engines (not sure of the make), one on top of the other. The lower engine was a backup and could be engaged with a belt if the main/top engine failed.
Your original question is one I have wondered about as well. I think you answered it with the comparison to a similar boat of yours. You are burning less fuel. The only question that remains is how much pollutants are you putting out compared to the additional fuel/pollutants the newer engine is putting out. Not sure that can be answered here.
The other factor to be considered is the longevity of the Garner engine and how this computes to having to replace and engine and the pollutants involved in that process.
For the record, I'd take the Garner engine any day of the week.
Your original question is one I have wondered about as well. I think you answered it with the comparison to a similar boat of yours. You are burning less fuel. The only question that remains is how much pollutants are you putting out compared to the additional fuel/pollutants the newer engine is putting out. Not sure that can be answered here.
The other factor to be considered is the longevity of the Garner engine and how this computes to having to replace and engine and the pollutants involved in that process.
For the record, I'd take the Garner engine any day of the week.
hollywood8118
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Thread drift..
Yes it was a 3000w generator head belted off the main engine. It had a adjustable pulley on the head and has mounted on a hinge arrangement that moved via a trim servo unit from a airplane. At the helm was a transfer switch that connected the unit to the boats ac system. The units output was adjusted to the rpm with a two way momentary switch while looking at a hz (cycle) meter. As I typically ran at the same rpm I would connect/disconnect the selector switch at the same engine rpm. I would fine tune the hz. with the trim servo. It worked exceptionally well, didn't eat belts and was engaged on every trip that went over an hour. The system worked flawlessly for my 9 years of ownership. I plan to recreate this on the next bluewater boat.
Hollywood
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California paid part of the replacement cost of commercial marine engines because they burned cleaner. Some of those new engines actually use more fuel. Few, if any, of the new engines are as reliable as the engines they replaced.
magna 6882
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Fun thread to read. I have no idea how one interpolates fuel burn on a boat. It seems hull shape and weight as one variable but likely more relevant would be prop design and pitch matched with certain rpms to hit the desired speed,less then hull speed and then at what rpm. On my boat with a newer cummins the injector timing changes at 2250 rpm. At lower rpms there are multiple squirts to help the engine run smooth so logically over 2250 would be less squirts but more rpm. If one were to design a boat to go at one steady speed, the smart guys could likely design a really efficient boat but likely still be in the same ballpark as the gardner
I would be very interested in the make and model of the adjustable pulley if you have it.
socalrider
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It is possible to find this data - I'm too lazy to search for it, but the answer is that the newer engines will pollute a lot less (criteria pollutants here, mainly NOx and PM but also unburned hydrocarbons).
Honestly though, unlike CO2, criteria pollutants matter most in populated areas - in the middle of the ocean it's not such a big deal if your engine is smoking away as that smoke will be diluted before it can harm anyone's lungs. In SoCal it's a different story.
One other aspect with which I'm less familiar is the impact on water quality (for underwater exhausts). I know an older diesel in bad repair will blow a lot of oil past the rings, which will end up in the water (this would be categorized as "unburned HC" in the criteria pollutant bucket). Again, a bigger issue in crowded waterways, or enclosed lakes like Tahoe. 2-stroke gassers are *horrible* in this regard.
OP
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Don't worry about the thread drift! That's how we learn things. On the genny setup above, that sounds like a pretty slick setup! Ours is a spline driven hyd pump on the front of the Gardner, either powering the bow thruster when docking/slowspeed maneuvering, or away from the dock, powering the 12kw 120v generator.
OP
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Mac, if the dual engine setup you speak of was two Mitsubishi engines, than I think I am familiar with the boat. It was similar to ours, but was extended 4.5' at the stern, and the backup engine has been removed. The boat is currently for sale, in Bremerton, WA.
What is the brand of the hydraulic generator?
I have been looking at these for years and wonder why people are not using them since they are used on emergency vehicles, mine, work trucks, military vehicles, etc. The only issue I can think of would be maintaining RPM, and thus voltage, but at least some of the brands I have seen, state they can maintain RPM and voltage.
Have you had any issues with your hydraulic generator?
Having a hydraulic pump to power:
- Thruster(s)
- Genset
- Wash down pump(s)
- Bilge pump(s)
- Windless(es)
- Winch(es)
Later,
Dan
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Bit of discussion on hydraulic Genset here
https://www.trawlerforum.com/forums/s4/load-dump-lifepo4-generator-battery-charger-62840.html
Yep, I saw how that discussion evolved to talk about the hydraulic generator and I posted a list of links to the equipment I had found over the years. Been thinking I should start a discussion about the hydraulic generators but then I saw slowgoesit's post, and I had to ask.
Later,
Dan
I had a very useful hydraulic cruise generator on my last boat.
It was driven by the main engine, a Perkins 4-236 of about 85 HP.
The pump was a variable displacement swashplate type like those used on big
rigs for refrigerated trailers. The generator was 5kW driven by hydraulic motors.
It was pretty simple and completely trouble free.
A good DIY'er could easily put one together. The Dynaset generator looks easier still.
The voltage stayed very steady once the main engine was above idle speed.
The pump output has to be matched to the generator size and motors used.
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fgarriso
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This is a quote directly form Gardner Marine Diesels on the 8LXB.
https://gardnermarine.com/engines/gardner-diesel-engine-8lxb/
This outstanding eight cylinder 13.93 litre engine offers the greatest degree of efficiency, durability and refinement. The specific fuel consumption rate of the engine when directly coupled to the dynamometer is the remarkably low value of 0.339 lb./per b.h.p./hour which represents an overall thermal efficiency of over 40%. The engine is designed for use with a fresh water closed circuit heat exchanger or keel cooler system.
Still in high demand today, and used worldwide in yachts, workboats.
They are rating their engines at "thermal efficiency" which I believe is the only accurate method of measuring an engines fuel efficiency.
https://gardnermarine.com/engines/gardner-diesel-engine-8lxb/
This outstanding eight cylinder 13.93 litre engine offers the greatest degree of efficiency, durability and refinement. The specific fuel consumption rate of the engine when directly coupled to the dynamometer is the remarkably low value of 0.339 lb./per b.h.p./hour which represents an overall thermal efficiency of over 40%. The engine is designed for use with a fresh water closed circuit heat exchanger or keel cooler system.
Still in high demand today, and used worldwide in yachts, workboats.
They are rating their engines at "thermal efficiency" which I believe is the only accurate method of measuring an engines fuel efficiency.
Slowmo
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As others have said fuel consumption comparisons like this are always dangerous. From an engineering view, no, modern diesels do not consume more fuel (and no, they're not set to run 'rich'). The efficiency of the diesel cycle engine is basically set by the compression ratio and how much (if any) excess fueling takes place. I could give a lengthily engineering dissertation as to why modern engines should be somewhat more, not less efficient . Much depends on how the operation of the engine is matched to the boat. In reality old engines can be quite efficient and people who expect to dramatically reduce fuel consumption with new engines may be disappointed, assuming it is 4 cycle to 4 cycle. The old DDC 2 cycles were a bit less efficient but had other advantages.
I believe that is the same boat. Looks like they did a big remodel from when I saw it at East Sound, Orcas Island. I always thought it was a cool engine arrangement, but I'm guessing the maintenance on the lower engine would have been a nightmare.
OP
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What is the brand of the hydraulic generator?
Later,
Dividing into Four major areas:
I can adjust the Hertz to 60 cycles by looking at a gauge, and turning a valve by the servo's to fine tune. For instance if I chose cruise rpm of 1300, then set it, then chose to bump my main engine rpm to 1400, I will have to manually set the hz down to obtain 60hz again.
- Hydraulic pump, attached to front of main engine via splined shaft, Eaton Model 70553.
- Electric/hydraulic servo's to first switch source of hydraulic pressure, either main engine, or backup Isuzu diesel engine. Then select destination appliance to use pressure: In our case, chose between bow thruster, generator, or get home hyd. motor which couples to main shaft via chain and sprockets in the event the main engine is disabled.
- Hydraulic motor, attached to generator: No data plate found
- Generator itself: Stamford 12 KVA, 120v, 100amp
One of the drawbacks of HYDRAULIC bow thrusters is that when you are most in need of the thruster, many times you are in slow speed maneuvers, say coming into dock, and therefore the main engine rpm is low, and your hyd pressure/flow will be low, resulting in a weak bow thruster response.
HOWEVER, since we have a CPP, docking is generally conducted with main engine rpm of around 1100, varying pitch for speed, and fwd, or rev. So we have plenty of hyd pressure for the bow thruster.
Enjoy!
1st pic, Gardner 8LXB main engine (pardon the mess in the ER) red hydraulic pump on front of engine.
2nd pic, HYD servo's
3rd pic, generator on left coupled to hyd motor on right
4th pic, close-up of generator data plate.
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hollywood8118
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Here is a very rough sketch( 1 min. max to make).
The main pulley was about 10", the adjustable one on the generator head was around 3" . I could get 60hz 120vac at 1200 rpm and above, but I never loaded it up at low Rpm's. I could run all day getting 3kw at cruising speed. It used a expensive Gates all green belt, around 5/8" wide. It sounds bad but I ran the same single belt of 9 years. The big frame Bus alternator on the engine ate a set of belts ( 2 belt setup) every couple years so I wasn't babying it.
Hope this helps
Hollywood
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ranger58sb
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rslifkin
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That's part of why the Gardners are as efficient as they are. When you don't try to optimize for power/weight ratio, physical size, a specific RPM range, or pretty much any other constraint, there's definitely a bit of durability and efficiency to be gained.
sunchaser
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Up until 35 to 40 years ago the bulk of the U.K. lorry and bus business was powered by Gardner diesels. The increasing price of diesel began to favor the more fuel efficient (as noted by the operators) Cummins and Perkins diesels. By the early 90's emissions regs started to take hold thus dooming Gardner excepting the strong marine side where continuous speed low RPM Gardners shined. It also helped that the small marine business was largely bereft of emissions standards for legacy engines.
In the 90's Perkins acquired Gardner, some say for the strong rebuild and parts business. About this time Gardner designed a turbo engine to compete with other builders. This "improvement" was not successful and Gardner morphed into a legacy engine builder and rebuilder with reasonable success to this day.
In the 90's Perkins acquired Gardner, some say for the strong rebuild and parts business. About this time Gardner designed a turbo engine to compete with other builders. This "improvement" was not successful and Gardner morphed into a legacy engine builder and rebuilder with reasonable success to this day.
fgarriso
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Very true. Gardners are very heavy for their HP range. The engine is rated at very low RPM with constant torque just above 1000 RPM. Works best with a variable pitch prop. The weight helps as the vessel requires less ballast as the engines are VERY heavy weights for their HP range. 
ProMaritime
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The poster answered his own question. It's all about man-made global warming, er I mean Climate Change. Like Watergate "Follow the money and all things will become crystal clear in time." Or was that from the move "The Godfather."
dathompson
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Richard, that duplicates our experience. Similar hull, QSB 5.9 rated @380 hp. We generally turn 1400 rpm. Guessing about 65 hp.
Oldsarge
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Yes, Bigger engines use more fuel. My Perkins 4-108 which is about 50 hP can push my 14 ton boat around just fine. However because it is a sailboat it doesn't do it very fast. I get about 12 miles or more to the gallon in average conditions at about 7 miles an hour.
ranger58sb
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I guess... but I'd also guess that some of the engine output is spent on dragging all that extra weight around...
-Chris
