Saving boat gas.

jrc · 06-20-2010, 04:19 PM

With due respect to NoBozo, I don't find GPH useful for determining the efficiency of my boating. It's way too dependent on speed. If I take an extra pass through the Weirs channel or Sally's gut my GPH will improve but I really havn't done anything to improve my boat operation.

You really need an fuel flow meter to monitor in real time. Say I want to boat over to Wolfeboro, what is best speed to go there. The very best speed will be around 5 MPH but that's four hours round trip. What's the best on-plane speed? I don't have the equipment, but I can guess it's better at 25 MPH than at 12 MPH. But my GPH will be better at 12 MPH.

brk-lnt · 06-21-2010, 05:56 PM

Quote:

Originally Posted by jrc

You really need an fuel flow meter to monitor in real time. Say I want to boat over to Wolfeboro, what is best speed to go there. The very best speed will be around 5 MPH but that's four hours round trip. What's the best on-plane speed? I don't have the equipment, but I can guess it's better at 25 MPH than at 12 MPH. But my GPH will be better at 12 MPH.

You're correct, but then you still have to do the final math...

Let's say at 5MPH you're burning 2GPH. To go 25 miles would take 5 hours. Hours x 2GPH would be 10 Gallons burned to make the trip.

At 25MPH you might be burning 9GPH. To go 25 miles would take 1 hour and you'd burn 9 gallons (making better time and less fuel than the 5MPH ride).

At 12MPH you might burn 6GPH. A 25 mile ride would take a little over 2 hours and 12 gallons.

(These are all just made-up numbers, but hopefully you get the idea).

You have to factor GPH, and time/distance.

NoBozo · 06-21-2010, 06:33 PM

I had a 32 foot.. 10,500 pound Sailboat over 25 years ago. I sailed it to Bermuda in 1981..but that is irrelevant. It had a 15HP Yanmar diesel. It burned 1/5 GPH. Yup..I'm not making this up....real world experience. That's ONE gallon every FIVE hours....BTW at 6 Knots.

I am an engineer and as such am obsessed with keeping records.

NB

brk-lnt · 06-21-2010, 07:18 PM

Quote:

Originally Posted by NoBozo

I had a 32 foot.. 10,500 pound Sailboat over 25 years ago. I sailed it to Bermuda in 1981..but that is irrelevant. It had a 15HP Yanmar diesel. It burned 1/5 GPH. Yup..I'm not making this up....real world experience. That's ONE gallon every FIVE hours....BTW at 6 Knots.

I am an engineer and as such am obsessed with keeping records.

NB

Not surprised at all. A diesel engine on a sailboat hull (which by design is generally engineered for minimal drag and high efficiency in the water), I find that totally believable.

jrc · 06-21-2010, 09:34 PM

brk-int, the fuel flow meter I have my eye on connects to my GPS and does all the math.

NoBozo, that's an impressive number. According to boattest.com, my boat uses about 7 times that at 6 knots.

I'm an engineer as well but I don't have records from that far back. Not that I had a boat in 1981.

06-21-2010, 06:33 PM	#3
NoBozo Senior Member Join Date: Jun 2008 Location: Portsmouth. RI Posts: 2,231 Thanks: 400 Thanked 460 Times in 308 Posts	Just to rile things up I had a 32 foot.. 10,500 pound Sailboat over 25 years ago. I sailed it to Bermuda in 1981..but that is irrelevant. It had a 15HP Yanmar diesel. It burned 1/5 GPH. Yup..I'm not making this up....real world experience. That's ONE gallon every FIVE hours....BTW at 6 Knots. I am an engineer and as such am obsessed with keeping records. NB

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06-20-2010, 04:19 PM	#1
jrc Senior Member Join Date: Apr 2004 Location: NH Posts: 2,689 Thanks: 33 Thanked 439 Times in 249 Posts	With due respect to NoBozo, I don't find GPH useful for determining the efficiency of my boating. It's way too dependent on speed. If I take an extra pass through the Weirs channel or Sally's gut my GPH will improve but I really havn't done anything to improve my boat operation. You really need an fuel flow meter to monitor in real time. Say I want to boat over to Wolfeboro, what is best speed to go there. The very best speed will be around 5 MPH but that's four hours round trip. What's the best on-plane speed? I don't have the equipment, but I can guess it's better at 25 MPH than at 12 MPH. But my GPH will be better at 12 MPH.

The Following User Says Thank You to jrc For This Useful Post:
Dave R (06-20-2010)

06-21-2010, 09:34 PM	#5
jrc Senior Member Join Date: Apr 2004 Location: NH Posts: 2,689 Thanks: 33 Thanked 439 Times in 249 Posts	brk-int, the fuel flow meter I have my eye on connects to my GPS and does all the math. NoBozo, that's an impressive number. According to boattest.com, my boat uses about 7 times that at 6 knots. I'm an engineer as well but I don't have records from that far back. Not that I had a boat in 1981.