Miles per gallon?

[BStack]

Guys,

I'm doing a river trip with my 2000 SAN and my buddy's 2001 SAN. There is a 90 mile stretch of water without a gas station. Any idea how many miles per gallon (going around 20 and with a light load) I could expect?

[mf01]

I typically estimate on GPH of about 3-5. We have slightly different boats, but I would say 5 MPG on the safe side. My estimate is 25 MPH at 5 GPH.

[DanielC]

I would suggest a little faster might improve your gas mileage. At 20 MPH, the boat is planing, but just barely. 25 MPH is maybe a little closer to optimum. If you are bored, do a test to see if 25 MPH is better than 20 MPH. However, I am assuming this is in a river. Do not forget to account for current.

90 miles at 20 MPH is 4.5 hours. 4.5 hours at 5 GPH is 22.5 gallons of gas. I think the tank is around 40 gallons? Your boat, you look it up.

If you run the boat out of gas, do this.
Put more gas in the tank. Turn the key on, do not try to start the engine. Repeat 5 or so times, then try to start the engine.

If you do run the boat out of gas, after getting it running again, sometime soon you will want to change the fuel filter. A lot of crud just stays in the tank, because the gas is sloshing around, and only the crud at the fuel pick up gets picked up. As the last bit of gas in the tank is used up, all the crud is in that small amount of gas, and is much more likely to get into the fuel system.

[TX-Foilhead]

If you don't have some sort of stump pulling prop, running somewhere between 25 to 30 will probably be best for fuel use. I don't know where the sweet spot is on the Chevy, but my 351 Ford seems to be happiest a little over 3000 RPM's. That seems to drop the fuel use age the most. Hard to believe, but I actually use less pulling foils @ 27 than I do pulling them at 20 to 22. Works out to about 10 gal (1/4 tank) or so for a full day.

[xrichard]

FWIW, back when I used to subscribe to boating magazines and they printed fuel consumption graphs, the planing boats consistently had the best "mileage" at 3500rpm +/- one or two hundred RPM (assuming the boat was on plane at that speed). In terms of MPG, this was often only a bit worse than idle speed. Between +/-10mph and planing and above 4000rpm were clearly the worst.

If I were budgeting for fuel over a long stretch, I would figure along the lines of what DanielC posted...5GPH...is realistic. I would probably then budget for 6GPH to be safe.

[HS]

carry a (full) spare gas can?

[bchesley]

I have averaged about 5 gallons per hour wakeboarding with a loaded boat for several years now. I have had gt-40 boats and big block boats and they are all really close. I know I am close because I keep mine in the boathouse and refuse to buy marina gas due to price. I load it in 5 gallon increments and usually go through 10 for a couple of hours riding.

[BStack]

Thanks guys. I think I'll put in a little closer to shorten the drive time a little - at least for this first trip. I'm also planning to bring a 5 gallon gas tank as a backup.

[AirTool]

Thanks guys. I think I'll put in a little closer to shorten the drive time a little - at least for this first trip. I'm also planning to bring a 5 gallon gas tank as a backup.

For safety reasons, pour the 5 gallons into your boat's tank as soon as there is room. Some ding dong buddies I had, fished so far offshore they carried extra tanks of gas. They were smart enough to pour the gas in as soon as they got to the first fishing spot then would float the tanks behind the boat while the fished. I'm not sure USCG would like that anymore but what the heck....its safer than having them in the boat.

By the way, FWIW, my dad and I once took a long isolated trip in a center console outboard fishing boat and we did all the engineering calculations mentioned above and figured we'd just make it. We were in the ICW which is basically a saltwater river and ended up using a surprisingly lower amount of fuel. We probably could have turned around and returned home.

If you get up on plane and cruise and keep the throttle mid way, boats are much more efficient. If you go slow, no good. If you go wide open, no good. When at cruising speed, if you notice big changes in throttle give only incremental speed increase....you are only wasting gas.

[Paublo]

I installed a fuel flow meter on my last boat because the gas gauge was worthless. But as a side note, it was very helpful while making longer runs up Lake Powell to swith the readout from gallons used to rate of use- gallons per hour. Of course just because the rate is lower, doesn't mean you go further. You have to look at distance traveled with gallons used. On that boat my best range was at 25-26 mph.