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Old 02-20-2015, 06:05 AM   #1
Al
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Jimmy 4-53 fuel burn

Greetings to the forum- Would like some idea of the fuel burn on a Jimmy 4-53 at 1600-1800-and 2100 RPM. More towards cruising RPM range. Weight of the boat approx 18000# 37/40 foot length say 12 foot beam and drawing 3.6 feet SD hull. I'd guess a 2:1 gear ratio.

Single or duel application welcome, or any additional data (hypothetical at this point) required.
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Al
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Old 02-20-2015, 07:08 AM   #2
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At 18000 lbs your boat would cruise (SL x .9 to 1.15 ) with about 30 hp.

With a 36 LWL that is about 6K.

30 hp is minor power for a Jimmy , all which need about a 60% load to run efficiently .

Get the specks for that engine as installed (injectors and timing will vary the output) and see how far off it is from ideal.

Probably (big guess) if the boat is single engine and built as a displacement boat , with a nice big prop, you will enjoy cruising at about 2 GPH , or so.

The usual rule of thumb is operating in its efficient range the DD 2 strokes will create 16hp for every gallon of fuel burned in an hour.

Some claim more modern engines can produce 20, but that requires it be operated at just the proper load and RPM , seldom seen on most boats as the engines are usually over sized which is not efficient.

The big advantage of the DD is their long life .
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Old 02-20-2015, 11:36 AM   #3
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depends on how fast you run it and how its is propped but most boats operate between 2-5 NMpg operated in reasonable manner at bow down speed.
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Old 02-20-2015, 04:55 PM   #4
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Here's a couple of references...also forum member Scary has a Hatteras 48LRC with twin 4-53's.

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Old 02-20-2015, 05:32 PM   #5
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From the DD 4-53 NA data sheet:

1,600 rpm 2.0 gph 23 hp
1,800 rpm 2.5 gph 34 hp
2,000 rpm 3.2 gph 46 hp
2,200 rpm 4.1 gph 62 hp

Due to the fuzzy nature of the curve I downloaded from boatdiesel, these values are probably +/- 10%.

David
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Old 02-20-2015, 05:48 PM   #6
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It will burn no where near 4gph. At that power settings it will blow your ears out and peel nearby paint. That's why they last forever. No one can stand the noise from running them hard.

j/k. Sorta.. Loud beast. And durable.

About 10-20% more fuel than a modern four stroke, but still pretty good.
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Old 02-20-2015, 07:26 PM   #7
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Quote:
Originally Posted by Ski in NC View Post
It will burn no where near 4gph. At that power settings it will blow your ears out and peel nearby paint. That's why they last forever. No one can stand the noise from running them hard.

j/k. Sorta.. Loud beast. And durable.

About 10-20% more fuel than a modern four stroke, but still pretty good.
I can relate to that. I grew up on a farm, and whilst sometimes sentimental about the 'good old days' the sound of a 2 stroke diesel is never part of the fond memory. To be fair, transmission whine was just as bad as the exhaust noise. But, I got through it and I still have some hearing ... what's that you're saying ... speak up, don't mumble....
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Old 02-20-2015, 07:59 PM   #8
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At rated power they are almost identical to modern 4 strokes in fuel burn. They are not so good when not used at rated power, like a pair of 8-71s in a trawler. If your pulling a net and using most of the power available they are on par with any Cat in that power range. Not as efficient at lower power usage.
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Old 02-20-2015, 08:03 PM   #9
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Another plus is that when used at rated output they will outlast any four stroke of the same size and rating by far, usage being equal. But they are loud, especially so the 53 series. Although the 8-53 was not as obnoxious due to a three lobe blower.
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Old 02-20-2015, 10:42 PM   #10
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Thanks Fellows, All good and very confirming to involvement by myself. More with "Log Broncs" that use this engine set to a high RPM to provide what is needed in rounding up and rafting logs. At the high consistent RPM settings the fuel burn was excessive in terms of gallons used per shift. Not really a good table to use and the cause for the question here on the forum.
Regards, the Forum didn't disappoint.

Al
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