89' 9.9 fuel economy

[Mr.Stuart]

this is just a general question, I'm wondering what kind of fuel economy I can expect out of my little Evinrude on a 12 foot aluminum boat, about how many hours of run time am I going to get out of a 6 gallon tank of gas?

 

[wbeaton]

Re: 89' 9.9 fuel economy

The rough formula is that gph at WOT are equivalent to 10% of the rated hp of the motor. Therefore, 10 hp = 1 gph or 6 hours at WOT.

I frequently get an entire weekend of fishing out of a 6 gal tank, but that includes trolling and still fishing.

 

[Mr.Stuart]

Re: 89' 9.9 fuel economy

Awe, that's more like it, using that formula for my 115 HP outboard would come out to 11.5 gallons an hour? ....I don't think my big motor uses that much, but when your out on the water with it, it sure seems like it, that's one of the reasons I wanted a smaller boat, gas is expensive, I can deal with a boat that will go 6 hours per tank, I think on the big boat, I get something like 4 hours for an 18 gallon tank.

 

[wbeaton]

Re: 89' 9.9 fuel economy

Its not a perfect formula, but its not too far off in most cases. However, most of us don't run at WOT all the time. If you back it down to cruising speed you get much better fuel economy.

 

[Mr.Stuart]

Re: 89' 9.9 fuel economy

the 115 horse tops out at about 5,500 RPM, which I think it pretty close to red line? if there is a red line, I uselly back the 115 down to about 4,200 and don't go past that RPM, I generally get around 4 hours of run time out of the 18 gallon tank. the 18 foot boat pretty much screams wih that 115, it will cruise at 45, and a couple of times it's come close to 50, but I'm also not sure how accurate the speedo is,

what's the RPM range on the 9.9?
on a little 12 foot aluminum, what kind of speed can I expect? I was thinking around 20 MPH

 

[wbeaton]

Re: 89' 9.9 fuel economy

I don't know for sure, but I'd say 4500-5500 is operating range for the 9.9 hp.

 

[Mr.Stuart]

Re: 89' 9.9 fuel economy

I don't know for sure, but I'd say 4500-5500 is operating range for the 9.9 hp.

ok, then as far as RPM, both engines are going to be about the same, I'll hook a tach to it, so I know what it's doing, I just need to get the boat out and run it. I'll have a better idea on what it can do this weekend.