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fuel consumption

G

Good Samaritan

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is there a standard rule of thumb to approx. gauge fuel usage on gas or diesel motors, single or double? I currently have a 24' cabin cruiser and am considering upgrading to a 37er with twin gas or diesel, diesel if I can swing it.
 
Its all depends greatly on hull design, weight, power, speed, and of course diesel or gas. There are too many variables. I will say that a diesel will usually get 2-3 times the mileage a gasser will
 
thank you for the reply, I read a somewhat complicated way to figure it out but approx. say a 225 hp will burn 22.5 gallons per hour at full speed give or take gas or diesel?
 
A WW II battleship burnt 200 gallons of fuel oil per mile at cruising speed! That should make you feel better.

Jeff
 
I am "assuming" based on research replies, "praying" that I will get on average about 20 gph at cruising speed of 20. this is based on a 37' - 42' and may vary based on diesel or gas. I appreciate the responses.
 
heres what I work on....on a good day, not to much wind or wave action...my 318's are turning in around 1.5- 1.75 mpg...thats based on a 23 knot cruising speed, turning around 2800 rpm
 
It sure isn't bad. My Silverton 34C gets about 0.9 miles per gallon, averaged over an entire season, for both Chrysler 360 engines. My cruise is 2800 rpm and that gives me about 18 statute miles per hour with a clean bottom.

Of course, I'm hauling around a closed bridge enclosure, furniture, dishes and silverware for 12 and enough pots and pans to feed a small army. Fill up the gas tank before we leave and we've added another 1,220 lbs and if we top off the water tank that's another 420 lbs.

Sure, we burn off some of that fuel weight while underway and our fuel mileage probably improves, but the average tells the story.

Oh, don't forget wind and tide. Both make a big difference in fuel mileage here in our neck of the woods.

Bill
 
Bill,
Just to clarify, is that 0.9 mpg total or per engine? I'm getting 2 mpg in my 25' Trojan w/225 318, as you say, averaged over the season.
The people I know with 35ish boats are getting around 0.75 mpg.
Dick
 
That's surely for both engines. My 32 footer with twin 360s gets about 1.2 MPG at 2,500 rpms/ 18 knots, but it's an aluminum boat and much lighter.

Jeff
 
Yep, that's the fuel usage for both engines over last season.

Year before last, when fuel prices here were even higher than they are now, we decided to save gas by slowing down to hull speed. That worked out to be about 7 miles per hour and when we ran at that speed consistently, we got about 1.2 MPG. Of course, it took forever to get anywhere. A two hour cruise took 4.5 hours and that got old pretty quickly.

Bill
 
its taken me a few years to get there...getting my wife to understand that we never leave the dock with out a full water tank.( bow mounted)..that she cannot bring half the house with her & the heavy items she does bring also get stowed in the bow..along with the tools..Gennie..fresh drinking water..tv etc. I also only run around with half a tank of fuel..I know if I'm only going out for a swim I dont need full tanks...
 
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