Diesel consumption.

[HUGOSALT]

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 dinghy..so comsuption may be close to yours
when you are towing dinghy.
Head wind and sea conditions will seriously impact fuel comsuption.

[celenoglu]

The consumption for a 30 HP engine at cruising speed is appproximately 1liters/mile

[copacabana]

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?

[JimsCAL]

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.

[Boasun]

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.

[travlineasy]

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,

Gary

[wescarroll]

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.

[cruisingdream]

Yanmar 3gmf, I use 20gal per YEAR, who needs a fuel gauge! Just raise those big white things & the boat goes.