Poor fuel economy on a 115 Evinrude

I very recently purchased a used boat. It is a 1979 Newman 17 foot tri-hull with a 115 Evinrude on it. I do not know what year the engine is for sure but the serial number is J0002572. I would like to know what year it is for sure so I can order a shop manual for it. <br />I thing that I am most concerned about is the amount of fuel it uses. The first time we took it out we pulled the kids on tubes for about 3 hours. We comsumed 18 gallon of gas in that amount of time. We use to have a 72 Larson V hull with a 1982 70 Evinrude and would only consume 12-14 gallon in the entire day of tubing. I had expected an increase in fuel consumption, but nothing like this. The engine ran great though. The prop is a 13x19 that is on it currently. <br />Any ideas to help find out the actual year of the motor and how to improve the fuel economy would be greatly appreciated!

Re: Poor fuel economy on a 115 Evinrude

A lot depends on the condition of hull, prop and load. Tho that does sound like a lot of fuel. You can lose power to one cylinder and can still run but use a lot of fuel. I might have a good mechanic check to make sure that you are running on all 4. You also need to check hull for integrety...if your flotation is saturated with water. Prop is in rough shape...many things to check to tune boat, but first thing make sure motor is good...just a Thought

Re: Poor fuel economy on a 115 Evinrude

Your rite in the ball park for fuel consumption. A 115 HP engine with carbs burns 13 gal per hour @ WOT,, That would amount to 29 gal. in 3 hours. OK, so your not running WOT.....<br />Actually, your using the norm for fuel......18 gal. is ok. If your not used to boat fuel consumption, rule of thumb is 4 times whatever the equivellent HP of a car engine.<br />They vetty thirsty......

Re: Poor fuel economy on a 115 Evinrude

I think the rule-of-thumb for fuel consumption for carbed 2 stroke engine iz 10% of rated hp per hour at wfo. (10 gph at wfo for 100 hp engine).<br /><br />c/6<br /><br />Hooty