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  Topic Review (Newest First)
07-12-2012 07:25 PM
Re: Diesel consumption.

Yanmar 3gmf, I use 20gal per YEAR, who needs a fuel gauge! Just raise those big white things & the boat goes.
07-12-2012 05:30 PM
Re: Diesel consumption.

A piece of clear fuel line run from the vent line above the tank to a tap below the bottom of the tank, vertically along the side where it can be easily observed makes a foolproof emergency fuel gauge.
07-12-2012 03:12 PM
Re: Diesel consumption.

I use the GPS/Plotter to determine the distance (over ground) I've traveled, always leave with a full tank of gas, then fill it when I return and calculate the gas consumption of the 30-HP Universal Atomic-4 at 2,000 RPM pushing my 33 Morgan O.I.. On average, it works out to about 12-MPG, which I believe is about as economical as I can expect - especially from a 35-year-old gasoline engine. I figure I have a conservative cruising range on the engine of about 300 miles. About 5 tanks of fuel will easily get me from Perryville,MD to Key West, FL.

My fuel gauges quit working last year, and I'm not about to replace them. I carry 35-gallons of gas in the tank, and now use a 1/4-inch wooden dowel with appropriate markings if I'm worried about the amount remaining in the tank. The stick has only been used on two occasions.

Good Luck,

07-11-2012 09:08 PM
Re: Diesel consumption.

You can be fairly acturate on fuel consumption By taking fuel soundings I.E. by stick or tape, before and after you have used the engine/generator. And tracking the data in an engine log. Over a period of time you will have an excellent idea of how much fuel you have used and what is left on board.
07-11-2012 08:38 AM
Re: Diesel consumption.

While the prop (and how well it has been sized) has a lot to do with consumption, an average of 1/2 gallon an hour for a 30-35 foot boat cruising at 5-6 knots in calm water is a good number. Note that consumption will increase significantly as you increase speed. And its not linear but roughly a cubic relationship. So reducing the speed (or RPM) by 20% cuts the power in half. That's why using the engine maximum rated power to estimate fuel consumption doesn't work.
07-11-2012 07:28 AM
Re: Diesel consumption.

Celenoglu, your calculation of 1 liter/mile seems a little high for a 30 hp engine. I have a 30 hp Yanmar in a fairly heavy 35ft boat and I burn 2 litres per hour at 2300 RPM, giving me 5 to 6 kts, depending on sea state. That means I am getting from 2.5 to 3 miles per liter. What engine do you have and what RPM do you cruise at?
07-11-2012 02:26 AM
Re: Diesel consumption.

The consumption for a 30 HP engine at cruising speed is appproximately 1liters/mile
07-11-2012 01:12 AM
Re: Diesel consumption.

For a rough comparison...
Last May on last leg of trip (Cape Cod Canal to Kittery Me.)
on a friends Hunter 33 with a Yanmar 2GM20, motored entire leg
in benign conditions at 1800-2200 rpm's (average 2000)
18 hours ...close to 75 n miles...used less than .4 gal. per hour
with ave. speed of hair over 4 knots.
Did not tow the comsuption may be close to yours
when you are towing dinghy.
Head wind and sea conditions will seriously impact fuel comsuption.
07-11-2012 12:00 AM
Re: Diesel consumption.

Originally Posted by flyingwelshman View Post
i guestimated about 2 litres per hour at 2000 rpm - that's about 1 gal(us) per two hours - pretty close.
by adding rpm to your sheet, you won't be "guestimating" - you'll know what your consumption is at various power points.

what size engine do you have and what size boat? Do you tow a dinghy?
25hp. 33' boat is about 7-8ton all up. Tow dink sometimes.

My point was / is that by tracking the actual consumption you will get to know what *your boat* consumes.
07-10-2012 11:47 PM
Re: Diesel consumption.


My boat has a functioning fuel gauge. I also have a functioning hour meter. From 6 years of use I know that I use, on average, about 1/2 gallon an hour. This is for a Universal M25 turning a 3 blade prop, and the boat is an O'day 35. I typically run the engine at 80% of max rpm. On my boat that means I move at about 6 kts.

Considering that I use my engine about 50 hours a year I start the season with a fuel tank, fill it again in August, and then at the end of the season.

Real simple.

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