River boating - gas usage?

[SkunkedAgain]

Hey,

I have never put into the Mississippi, but plan to take a nice cruise up and down the river next weekend - just for sightseeing. My big question is: How much more fuel can I expect to use going upstream versus downstream?

I don't want to get stuck without enough fuel to get back. I know that each boat/motor is different, but I'm just looking for a ratio. Will I use twice as much fuel? Three times as much? If it really matters, I've got a 1985 Fisher 16.5ft with a '79 Evinrude 35hp.

I know that the best solution is to drive downstream and then boat upstream first, but I don't really want to drive that far.

[hanson]

I guess I wouldn't really worry about it right now. You will use a tad more going upstream but with the low water level and low flow right now, it will be marginal at best.

[Rivernut]

I agree. I run the rivers about half of my fifhing time, and with the low water and slower current, you"ll be fine. You will use a little more, but it will be fine. How many miles were you planning on running, round trip?

[SkunkedAgain]

Probably from Mpls down to St. Paul and back...depending on how far I can get on my two 6 gallon tanks. So essentially I can use most of a tank on the way down, save a little, and use the rest to get back. That's great to know.

Thanks all.

[Shack]

I would always head up stream!

I would turn back when you hit half tank (starting on a full tank)!

You will make it then.

[dps]

Quote:

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I would always head up stream!

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Wise words!

There is hardly no current on the river right now... wind might effect your milage more

Your 35hp motor doesnt eat much gas if your not at WOT. Cruising on plane somewhere around 2/3 throttle is usually best for fuel economy.

If your crising around the cities, I would launch around 494 and head upstream into pool 1(through the locks) if your just out for a long cruise. Stay between the channel marker buoys! There is a gas pump at watergate marina if your questioning your fuel level.

[lotsofish]

If you run at "cruising speed" (like 1/2 - 2/3 throttle) you should be able to get at least 20-25 miles on one 6 gallon tank, maybe a little more.

[chickeywing]

My experience is pushing the 3:1 ratio. This spring, on the GPS, there was about a 4-5 MPH difference between upstream and downstream on the Crow River. From the looks of the picts on the TV, the Miss is flowing faster than the Crow was. It's always a good idea to motor upstream first. Bite the bullet and drive farther so you can run out of gas and drift back to the launch. It's a long way to New Orleans!

TC

[Dave B]

The river is now closed upriver of the Ford Dam, so I would hold off you your trip.

[SkunkedAgain]

That's what I was worried about. Thanks for the notice.

[wastewaterguru]

Pretty easy to figure the exact number if you know the current speed.

Drive WOT upstream and record speed.

Then drive WOT down and record speed.

Difference divided by two is approximately the current speed.

So the equation for the fuel usage difference is simple.....

If you are getting speed from a paddlewheel or pressure type unit that is measuring water speed then the equation is the following......

(Speed + Current Speed) divided by (Speed - Current Speed) = Fuel use ratio.

Let's say the boat does 30 mph indicated.

Current speed is 4 mph.

Then (30 + 4) / (30 - 4) = 1.307

It takes 1.3 times the amount of fuel going upriver then downriver.....or 30% more.

If using GPS for speed determination, then fuel use ratio is simply the downstream speed divided by the upstream speed.

GPS indicates 34 mph downstream and 26 upstream.....

This means there is a 4 mph current.

34/26 = 1.3 (same result - 30% more fuel going upstream.)