Improving fuel economy on an 115 2T

[axolotl98]

Hi.
Motor runs fine with service and winterization done every season.
Its consumption is a mean of 1,2 liters per nautical mile which can go up to 1,5 if it gets really choppy.

Is there any magical way to make it burn less fuel ?
Change jets at carbs or even change carbs ?
Port the block ? Change exhaust innards ?

I am probably asking for the impossible but maybe Rodbolt has an ace up his sleeve...
Could go for a newer technology engine, but the simplicity of my Yam, as well as the fact that it is a 91 mod but in mint condition and I can personally do most maintenance puts me completely off of this path...

[rodbolt17]

nope
not much to do.
make sure its propped correctly for THAT trips load.
shed all the hull weight you can.
wax the hull.
pay for the gas.
at or near its rated HP it will burn 10-12 gallons per hour.

[robert graham]

Check "Yamaha Outboard Performance Bulletins" for your boat/motor rig and try to cruise in the most efficient RPM range. Best MPG on my boat is about 3500 RPM's, so going slow or going fast is not necessarily the best mileage. Good Luck!

[99yam40]

proper Motor set up on boat and proper prop is a must.

May need to find smaller/ lighter boat and prop it for that one to get better fuel mileage.
But like Robert said finding the right RPM to run the set up with that load is the key.
Maybe this site will help figure it out. See if you can find something close to what you have
Performance Bulletins | Yamaha Outboards

[axolotl98]

Right.
Current prop is a 19 Ballistic, which maxes a trimmed-out motor at 5300 with normal loads at 42 knts.
And I enjoy cruising at 4000 which is about 28 knts.

Downgrading to the original Yam 17 inch will give me a max rpm of over 6000.

The million dollar question. Considering a careful use of the motor (not above 5500) will then the motor be more economical (liter per hour) to run at 4000 rpm ? Will it be more economical in liter per n.mile ? Or the actual difference is not worth considering ?