1991 50hp mercury mariner

I have a 1991 mercury mariner 50 hp. and it is on a 24ft. pontoon and it is a gas hog. It runs really good. I have rebuilt the carbs, new plugs and no fuel leaks. It has lots of power. I ran the boat for about 3 hours and only full throttle for a short time. Most of the time was 1/2 throttle or a little less and it drank about 4 gal. of gas.

Maybe I'm expecting better millage. If anyone has any info or that is the way it is let me know.

Thanks

That sounds very normal , in fact that is excellent mileage !!

Agree, that is awesome gas mileage.

Some very loose "rules of thumb".

Divide your "horses" by 10 and that's how much you will burn (in gallons per hour) at full throttle.

So 50 horses = 5 gallons/hour

At about 2/3's throttle (maximum timing advance, but still have some throttle left), you can cut your consumption to about 50-60% of max.

So for a 50, burning 3 gallons per hour "at cruise speed" would be considered "good/typical/normal".

My 140 horse can drain my 80 gallons of tanks (twin 40's) in a little under 6 hours if I open her up - even at cruise they are empty after about 11 hours of running. Boats are expensive toys, and in Canada as of today, gas is selling for $3.90 a gallon - so forgive me if I "don't feel your pain"