Anyone know roughly how many mpg a 15 hp 2 stroke Johnson would get on a 14’ jon boat? I’m planning a 20 mile round trip this weekend and want to make sure my 6 gallon tank will cover it.

 

About all I can find is that you should burn 1 gallon per 10 horsepower an hour at wide open throttle. This would imply 4 hours of running at 15 mph with the tank or 60 miles total.

 

I haven’t really kept up with how much gas I’ve used up to this point, just fill it up when needed but 60 miles on 6 gallons sounds pretty high to me.

MPG is almost impossible to figure out for a boat...it's always HPG (hours per gallon). So many variables can change how many miles you go...wind, current, wave action, is the motor height/angle set properly, how much weight is in the boat, is it planing?

I did some searching once and found an outboard engine test website where you could choose your outboard and prop, then choose between several hull types and come up with rough fuel consumption figures.

 

Some of the thriftier combos did actually show an estimated MPG rating.  (My 2014 Mercury 40HP four-cycle on my Tracker Pro170 can --and does-- get over 10MPG!)

6 gallons will last all day with a 15 hp, but as posted above, MPGs are hard to nail down. Easy enough to take an extra 2 gallons or so, (got a lawnmower?).

Don’t run it wide open and you’ll be fine. Get up to wide open then back off a touch