MPG or GPH

[askipper3]

I need to find just how much Gallons I burn.

Either in MPG or GPH. Either is good.

I have a 84' 20SF w/ 2004 150 Merc. 2-stoke Carb.

Does anyone have a "rough" estimate- or is their an easy way to find out?

[NoBones]

Maybe fill the tank, run for an hour. Log your GPS.
Fill the tank again. Note your load and speed as it will vary depending on all that as well as wind and tide.
Or buy a Flo scan....

See ya, Ken

[JohnB]

Flo scan is the way to go. It will pay for itself in 20 trips or less. You can change the trim/rpm/tabs on the boat to get the most economical speed based on load in the boat and sea conditions. If I run mine at 4400 rpm, I am at about 30 mph getting 1.6 mpg, if I bump it back to 3800, I run about 26 mph, but get close to 2 mpg. On an average trip, I run 100 miles, the difference is over 12 gallons, at 4 bucks a gallon, thats 48 dollars, by just slowing down 4 mph or so.

[peterb]

Like JohnB said, once you have a device that gives you realtime feedback it's amazing how the little things add up (such as tweaking the tabs and finding the optimal speed range, which may be different than the engines suggest).

With my boat the RPM's and MPH speed are pretty close to one another (except at the top range when I am going 57 MPH at 5,300 RPM's).

I have twin Yamaha 0X66's and average between 1.6 and 1.8 Mles per gallon when cruising. If I bump the engines to above 4,200 RPM's the engines purr like kittens but start to swill the gas. I would not have not known this if it weren't for the fuel mgmt. system.

[3rdday]

take a 1,2 0r 5 gallon reserve tank. Drop your fuel line into that and run it dry. Use a GPS to log your miles.
You can try a 1 tank on cruise, another on WOT, etc.

[Fr. Frank]

Get a fuel flow meter, really. I run a '92 Merc 150 carb, on a 20' Seafari and I improved my overall fuel economy by over 50% with my Navman.

[askipper3]

Navman?

[76Red18]

Navman?

Fr. Frank, I was looking at the Northstar Fuel 310 system. Uses GPS data to calculate mileage. Around $350. What do you think?

[Fr. Frank]

I went cheap, and bought a Navman 210 a couple of years ago, for $99, from PlanetGPS. Since the changeover to "Northstar", I understand prices have gone up.
If you don't mind 3 minutes with a calculator, it's great.

But if you're willing to pay an additional $250 to have the machine do the calculations, AND you don't mind having to have a square box, instead of a neat 2 1/8" flush mount in your console of dash, go ahead and get the 310.

[76Red18]

I figured the optimal throttle setting would constanty change due to load,wind,current,etc..After more digging ,I have found a 310 for $238. Mind posting the formula for the calcs.? Thanks for your input