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Old 05-02-2008, 07:10   #16
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15 years with a 3gm30 on our 34' 13000# monohull: 2100 RPM = .3-.4GPM, 2500 RPM = .6 -.7GPM. We installed an Autoprop several years back and I think it increased fuel GPM a bit, but we also gained 1K at same RPM.
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Old 05-02-2008, 10:23   #17
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On ours we've got just over 100 gallons in two SS tanks (something like 52 gallons for each engine). We also carry approx 50 gallons in jerry cans, plus another 20 gallons in a dedicated genset tank.
And that's on a SAIL boat???? Good lord, what's that big sitck for?

Oh wait... it's a cruising catamaran...
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Old 05-02-2008, 11:18   #18
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Navman make a good, in fact very good, affordable fuel measurement system. About the most accurate you will get for the "amature" market.
Engine fuel use should be measured in a x?/hr bases. A boat has to many variables working with or against it to measure fuel usage based on distance.
As already stated, the manufacturer will or should have a fuel curve published. If the manufacturer was really good, they will have several curves on that Graph. That is because there are several different standards in use. For instance, Hp! There is Brake Hp, Shaft Hp, metric Hp, SAE Hp. I think that's all. Then there are two main loads applied that vary. The bench tested load is pretty much linear. But on a boat, you have a Propellor law curve. This means a non-linear load. Of course to make things even more difficult, that law varies with water temp and Salinity.
Then the are variables to the engine bench test. A specific weight of oil is used for lubrication. The fuel oil has to be a specific temperature. Temp has a big variance on volume of fuel. It goes on.
This is one reason why up untill now, fuel usage computers were for the proffesional market. It was vary expensive to accurately calculate Fuel use because of something as simple as temperature. Navman have made a very affordable unit that gets around this problem.
But aside from all the above, for all Diesel engines, it is ruffly accurate enough that a given dose of fuel will result in producing a given "bang". I have said this before, but I need to dig out my old theory papers and find the exact quantities of fuel dose. I have the numbers for each injector squirt and per Hp and Per Revs and so on. It is interesting to see that no matter what engine it is, all of them are very close to the same. However, my theory papers are before the days of Electronic controlled injection/high pressure rails. So I can't comment on them, accurately at least.
Unlike a Petrol(gasoline) engine, load has a lot less influence on the fuel usage. About a 20% increase between loaded and uloaded. Petrol can be as much as 80%. The newer computer controlled engines are a little more efficient, because they have been able to produce a more steady HP/torque range over a wider variance of RPM. Thus giving a better power drive to the water over a greater RPM.
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Old 05-02-2008, 17:28   #19
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I have two 28 gallon fuel tanks. When I am cruising, I carry 6 5.5 gallon plastic diesel fuel cans. I carry 2 5.5 gallon plastic gas cans. The gas is for the dinghy and the portable generator. After 1 long day of running (about 9 - 10 hours) I'll take 1 can of diesel and top up the tank I just drew from. If I am doing a constant run, I will use 2 can in 24 hours. I like to try to sail when I am doing long runs like that.

These cans are carried on the deck, tied to my safety lines. 4 on each side.
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Old 05-02-2008, 17:37   #20
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About half way through my watch, I take my flashlight, set it up against the plastic fuel tanks and make note of the level. If it is half way or more, I dump another can (5.5 gallons or so into that tank). Some fuel managment program, huh?

My rational is it never hurts to have fuel in the tank where it can do you some good. Fuel sitting in the jugs, is not very useful! Actually thought I was running out of fuel once. Engine RPM started to go down unaccountably. Switched to the other engine, checked out what was going on below. Ends up it was a clogged primary filter. Changed the filter, no problem!

It is rather essential that one have a good sense of their fuel consumption to do trip planning. What worked for me is extended runs and them measure the amount of fuel it took to top up. I noted the travel distance and times and that has let me get a very good feel for what I am consuming. When I have an abberation in my metrics, I look for the cause.
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Old 05-02-2008, 17:39   #21
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Oh yeah! The size of my tanks suck! I'd really much perfer larger fuel tanks with greater capacity. I guess, I can't have everything!
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Old 12-02-2008, 07:51   #22
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On Imagine we get right at 3/4 a gallon betwen both engines @2000 rpm doing between 7 & 8 knots. Above each engine is a 20 gallon tank, and we carry another 40 gallons in jugs. This is with the 3GM motors.
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Old 11-09-2010, 18:05   #23
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Yanmar 3GM30 fuel burn

We just installed a newly reconditioned 3GM30 on our C&C 32 this summer. What a wonderful difference from the old 2GM!! Hull speed with half the noise and vibration. we have a Campbell Sailor 15x9 3 blade prop, and averaged just over 2 litres per hour (over 160 engine hours) at 2500 rpm. Hope this helps.
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Old 30-09-2011, 05:41   #24
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Re: Gallons / Hour with a Yanmar 3gm30

I have two 3gm30s driving through brunton autoprops.

The boat has 4 x 17.5 gallon (or 21 US gallon) tanks


recent motor passage with a very dirty bottom, shows just over 1/2 UK gallon per hour at 2200 revs to achieve about 6 knots. However, the props are definitely over pitched.

I would love to change to 3YM30 for the additional power in order to balance the larger alternators that are fitted.
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Old 28-01-2012, 18:26   #25
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Re: Gallons / Hour with a Yanmar 3gm30

So after reading the 2 pages on this thread it seems that people are happy with this motor?
Any issues worth noting?
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Old 28-01-2012, 20:27   #26
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Re: Gallons / Hour with a Yanmar 3gm30

Happy with the motor. Between 1/2 to 3/4 gph at 8 knots with an 11,000 # Searunner trimaran. Quiet, clean, low vibration. Perfect.
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Old 28-01-2012, 21:14   #27
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Re: Gallons / Hour with a Yanmar 3gm30

1,000 gal/hr @ 900 rpm, not a Yanmar though.
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Old 29-01-2012, 01:52   #28
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Re: Gallons / Hour with a Yanmar 3gm30

I'm just bought a sailboat with the 3gm30.
The boat has been parked on the hard for 2.5 years.
The motor is said to have run perfectly and has only 200 hrs.
Visually she looks great.

Any mechanical concerns before the boat is splashed other than fuel condition?
Can I run the motor on the hard?

Thanks
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Old 29-01-2012, 06:13   #29
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Re: Gallons / Hour with a Yanmar 3gm30

Quote:
Originally Posted by endoftheroad View Post
I'm just bought a sailboat with the 3gm30.
The boat has been parked on the hard for 2.5 years.
The motor is said to have run perfectly and has only 200 hrs.
Visually she looks great.

Any mechanical concerns before the boat is splashed other than fuel condition?
Can I run the motor on the hard?

Thanks
Yes you can run it on the hard, just pull the intake to the raw water pump and put a water hose in it- I would replace the impeller on the raw water pump and change the oil/filter at the least
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Old 29-01-2012, 11:12   #30
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Re: Gallons / Hour with a Yanmar 3gm30

Put the compression release levers up, spray some wd40 into the air intake, move the flywheel by hand, and confirm that nothing has rusted (much) before firing up the engine. Once you get the engine warmed up, change the oil and filter. Be sure that the fuel filter is drained of water and that the line is bled.
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