Mileage

[JEBar]

I'm looking for a reasonably priced, aftermarket device that can be hooked up to an outboard powered boat's fuel system which will tell the motor's fuel consumption .... as in gallons per hour or better yet miles per gallon .... we hope to be making some cruises on various rivers across the country and it would really help in planning for refueling .... recommendations would be appreciated

Jim

 

[Scott Danforth]

Re: Mileage

your talking about a fuel flow meter. such as floscan. they are in-line between the engine and fuel tank.

that is how boattest.com gets fuel consumption information.

 

[Fireman431]

Re: Mileage

Like Scott posted, look to www.floscan.com and find the one that fits your engine. It will be in GPH burned, not MPG.

 

[JEBar]

Re: Mileage

quick response really appreciated .... in looking at the link and it will take me while to sort though all of the ones listed

Jim

 

[Fireman431]

Re: Mileage

Give some specs on your boat if you need assistance.

 

[CaptainKickback]

Re: Mileage

Does your boat have a GPS? A number of the newer GPSs can display the fuel flow data, which means you only have to by the sending unit.

I plan to use a Garmin sender across a NMEA 2000 network to my GPS on my project boat. About $120 for the sender.

Sea ya...

 

[oops!]

Re: Mileage

you wil not see a MPG rating on a boat... due to the variable prop pitch size and prop slip.... everything is in gph

 

[CaptainKickback]

Re: Mileage

oops! I didn't know you were a GPH Only guy. Waiting for QC to jump in now that you brought up GPH. lol

But JEBar, oops! is right. The sender will only give you GPH. But, with more input, you can calculate MPH at different RPMs. You will get different values at different RPM, and remember, wind and current will affect the numbers on any given cruise.

However, a lot of the new GPSs, knowing speed and distance, can calculate your MPG instantly.

Sea ya...

 

[Scott Danforth]

Re: Mileage

I usually calculate need based on 2 miles per gallon. that covers the WOT runs, cruising runs, and idling around. I get better economy than that, however it helps hit the 1/3 rule.

 

[Mischief Managed]

Re: Mileage

you wil not see a MPG rating on a boat... due to the variable prop pitch size and prop slip.... everything is in gph

My Lowrance LMF-200 displays GPH and MPG (as well as speed, fuel used for the season, fuel remaining in the tank, and range). MPG is easy to figure if you know your GPH and speed. MPG is much more useful than GPH since it tells you your true economy. I tweak my trim using the MPG function.

 

[Howard Sterndrive]

Re: Mileage

My Lowrance LMF-200 displays GPH and MPG

definitely affordable otion, although I question the accuracy at trolling speeds.
I never bothered to learn all the LMF200 features... I find it very unintuitive, evidence by things like GND:S meaning ground speed (why?....not designed with english in mind I suppose)
this is how I left mine set as I was pretty happy when I got this figured out:

 

[Mischief Managed]

Re: Mileage

definitely affordable otion, although I question the accuracy at trolling speeds.

I've had mine for 4 or 5 seasons now. The fuel flow accuracy has been better then 99% the whole time. I never fill my gas tank anymore, I just add what I need for the day to the 15 to 20 gallons I leave in reserve. I can routinely run 150lbs lighter this way.

 

[Fireman431]

Re: Mileage

MPG is a useless measurement of fuel burn unless you run the EXACT same weight, EXACT same RPM, EXACT same loading, all in the EXACT same wind and current. You would also have to determine this MPG at 500 RPM intervals as it is constantly going to change.

Since boats run in variable states and varying RPMs, get your median fuel burn moderately loaded at cruising speed and go from there. Also, the GPH fuel use meter will change with each increase or decrease in RPM, giving you immediate reports. It's simply a paddlewheel spun by fuel flowing.

 

[Howard Sterndrive]

Re: Mileage

mpg pretty valuable to me. I used to cruise at 3400 to 3500 rpm because most reports showed the best economy at that speed. I slowed to 3100 to 3250 after installing the gauge. I get almost 1 mpg better at the new speed.
my hull's sweet spot I suppose

to me gph are not very useful. I want to get the best mileage.

 

[Mischief Managed]

Re: Mileage

MPG is a useless measurement of fuel burn unless you run the EXACT same weight, EXACT same RPM, EXACT same loading, all in the EXACT same wind and current. You would also have to determine this MPG at 500 RPM intervals as it is constantly going to change.

Since boats run in variable states and varying RPMs, get your median fuel burn moderately loaded at cruising speed and go from there. Also, the GPH fuel use meter will change with each increase or decrease in RPM, giving you immediate reports. It's simply a paddlewheel spun by fuel flowing.

Instantaneous MPG is very useful to me. I can tell in a second how my trim or speed adjustments have affected my fuel efficiency. My boat, for instance, is quite a bit more efficient at 33 MPH than it is at 28 MPH, with a typical load. You'd think a 5 MPH increase in speed on plane would adversely affect efficiency but it does not on my boat. Might be a stepped-hull thing???

 

[Jlawsen]

Re: Mileage

I'm looking for a reasonably priced, aftermarket device that can be hooked up to an outboard powered boat's fuel system which will tell the motor's fuel consumption .... as in gallons per hour or better yet miles per gallon .... we hope to be making some cruises on various rivers across the country and it would really help in planning for refueling .... recommendations would be appreciated

Jim

Boy or Boy, this is actually a lot more difficult to accomplish than you think. Things like a strong wind comming up in the middle of your run can throw you all out of whack. Up stream, down stream is going to make a difference also. The rule of 1/3 out 1/3 back and 1/3 reserve is your start point but just how far can you go on 1/3 tank?

I have to agree with and actually do have the flowscan system through my Lowrance HDS-8 and I have SmartCraft that gives me a second reference. To be honest though I installed it and set it up once and then realized I had no use for it. The later is not the case for you though, it's just what I found. I can stick with the rule of thirds and do just fine with a analog fuel gauge.

The only reason I'm throwing that out there is because it just might be easier for you.

 

[CaptainKickback]

Re: Mileage

Howard Sterndrive: the ground (bottom) speed is what you are measuring if you are getting that number from your gps.

Fireman: all you said is relatively true except for the word "useless". At any given speed, you can tweak up or down to see if you get a little better economy. You can determine the particular boat's sweet spot. And gph alone means nothing. If you were burning 10 gph and increase to 15 gph, what does that tell you? Nothing except you are burning more fuel. Now if you know your speed before and after, you can get some meaningf information.

Sea ya...

 

[QC]

Re: Mileage

I always say, ultimately you need to know where you are going to run out of fuel, not when GPH means nothing without speed. With speed you have MPG and then you have something you can use. There you go Kickback

 

[Fireman431]

Re: Mileage

There is not a boat out there that is going to tell you MPG. Even the new cars that do this are telling you GPH/60. Let off the gas or accelerate and watch how they change. If you want MPG, do the math. I'm just saying that MPG is going to be impossible to determine unless all things are equal, which they are not going to be. Using GPH, your relative speed, RPM, and trim setting is going to be the only way to determine your fuel usage at a given RPM, regardless of the math you use to get there. Install the gauge, find your sweet spot (RPM & speed & fuel burn) and caculate your use with that.

 

[CaptainKickback]

Re: Mileage

There is not a boat out there that is going to tell you MPG. Even the new cars that do this are telling you GPH/60. Let off the gas or accelerate and watch how they change. If you want MPG, do the math. I'm just saying that MPG is going to be impossible to determine unless all things are equal, which they are not going to be. Using GPH, your relative speed, RPM, and trim setting is going to be the only way to determine your fuel usage at a given RPM, regardless of the math you use to get there. Install the gauge, find your sweet spot (RPM & speed & fuel burn) and caculate your use with that.

I think we are talking about different things here. Your point is well taken that there are many variables, most of which could change at any instant, where I am talking about the gps calculating instantaneous mpg (which they do) and that someone that only states gph is not providing meaningful information. You, yourself included "speed" in your post.

The "gph only" versus mpg discussion has been repeated repeatedly (deja vu al over again) on iboats (and probably elsewhere).

Sea ya...