9.9 Johnson fuel usage

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DMGO

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I just got a 96 Johnson 9.9. I am noticing very high fuel usage. A 3-gallon tank will run 1 1/2 hours at full throttle. Isn't that a LOT of fuel for this small outboard? What can I do to increase efficiency? All I did so far is new plugs, impeller, and changed lower unit oil.
 
What hull are you running? Do you happen to know the weight of passengers and cargo? RPM at WOT? Shaft length and transom height?
 
Back off the throttle from wide open! That will definitely change your mileage.
As for the other comments...the engine does not know whether or not it is pushing the Queen Mary or a 10' Jon Boat as long as the prop on it allows the engine to attain WOT RPM range. At that point fuel usage (GPH) will be the same.
GPH and MPG are totally different however and that is where your prop will come in. Pick a prop that will allow your engine to reach max RPM range as outlined in your owners manual. Once propped correctly then back off from the WOT setting and your GPH will drop and MPG will go up. Running that engine at WOT all the time will definitely shorten the life of it. If that is a must for you then add extra oil to your mix for protection.
 
I've had my 9.9 out a few times this year and haven't hardly nudged the fuel in my tank with about half an hour of run time and maybe half of that at WOT.
Like said previously, check your prop and see if you have the larger carb. Unless you're pushing a 16' deep v it seams much to me.
 

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