Anyone remember that CC fuel efficiency chart?

A few years ago there was a discussion here about fuel efficiency and speed of the boat.

The bottom line was when a chart was posted from tests conducted by CC that demonstrated that a boat loses efficiency the faster it goes. In terms of miles per gallon, it goes down the faster you go.

For example, if you are a long ways from the ramp, and very low on fuel, you are most likely to make it there if you go at idle speed. There is no speed that is more efficient in terms of distance.

Anyone remember that chart? Where can I find it?

I could not find it doing my own search.

"For example, if you are a long ways from the ramp, and very low on fuel, you are most likely to make it there if you go at idle speed. There is no speed that is more efficient in terms of distance."

I'd have to respectfully disagree with that.

Maybe in terms of GPH you're better of at idle, but I would bet the lowest RPM's your boat will plane at is the most efficient for MPG.

I would be interested in seeing such a chart myself, and I'll gladly eat crow!

You've piqued my interest. I never gave this any thought, but I'd be interested in knowing. I've got a book at home which might provide some generalizations. I'll look at it tonight and share if it says anything on this (I shouldn't be on the Internet now so I'll not search at this time).

We've got a freeze warning tonight so it's not wakeboard season, but it is fishing season. I've been out five times in last three weeks, long-line trolling with an 8 hp outboard (yamaha 4-stroke) for white bass and walleye.

It takes me 20 minutes at WOT (~12-13 mph) to get there, same amount of time back, and then I idle at the lowest rpm for the rest of time (which by the way is too fast, I have a DIY sea brake for drag to control speed, monitored by GPS).

My average trip is 4 hours long -- the motor is running continuosly the whole time (it is never shut off). My total fuel consumption for the first three trips was 2-1/2 gallons !!! This has been consistently so over the last several years. Over the years I consitently see that a typical trip uses about 3/4 a gallon or so.

I searched a bit and found this:

"Any attempt to force a displacement hull beyond its maximum theoretical hull speed brings exponentially higher fuel consumption for minimal gain in speed. On the other hand, slowing down a little almost always is rewarded by gains in economy, and thus range. This same principle applies to high-speed planing hulls as well but only up to the point at which they start to come off plane. Once off plane they tend to lose efficiency."

Did Dane post it? He has had some good charts on several of his posts.

I know that with most cars the efficiency in terms of MPG's is a bell curve with the peak around 45/50 mph.

I would imagine its a little different on a boat since there are no gears (sorry Mb's) but generally the more RPM's you run, the faster you are going, the more gas you use.... so if your boat I would bet if you go:
10 mph @ 1000 rpm
20 mph @ 2000 rpm
30 mph @ 3000 rpm
40 mph @ 4000 rpm it will all equal out. You go four times faster at 40 but use 4 times as much gas. Everything should equal out except stopped but running/barely idle and flat out redline

(Just can't stay away). I think wakeboard-boat hulls are semi-displacement. An ocean liner would represent a displacement hull. A bass boat would represent a planing hull. I don't recall if there would be (along with semi-displacement) a second or third intermediate category between the extremes.

Hi Chris, do you like your crow roasted or brazed?

This is from http://boattest.com/ for the Tige 22ve.

It's pretty typical of most boats, and particularly of inboards.

Maximum Miles/Gallon is at slow idle. It drops off rapidly while pushing water inefficiently and starts to improve when the boat starts to plane. Best normal speed is when it's on full plane but not working the engine hard.
If you're carrying weight you bump up the speed chart because it takes you longer to get on plane.

Here is the test for a 2006 X-45 Mastercraft.


Big boats suck back much more gas.

LOL Art!
I was afraid you'd chime in with some scientific data.
So limping home at 600 RPM gets you back to the dock with the most fuel left, but way after dark and the pumps are closed!
... I'll take my chances at 25 MPH getting 4MPG, rather than 4MPH getting 5.5 MPG hahaha

BTW - I like my crow BBQ'd

(Message edited by rio_sanger on April 06, 2009)

Looks like on the X-45, you get roughly the same MPG whether you go 18mph or 32 mph.
That is odd.

The Tige chart makes a lot of sense. The X-45 chart seems off.