oil/gas ratio too rich...

Just happy to find out that my 25 hp 2 stroke is about 25 to 30 percent easier on gas since i set my ratio to 100:1.

I tought i made a bad decision buying 2 stroke engine since the motor was a pig on gas(with 50 to 40:1 ratio) but after i set that to the specs; more power, more fuel efficient

[99yam40]

I have not seen a motor that runs 100:1. What model is this motor of yours.
THe rule of thumb is 1/10 of the hp is the WOT GPH that it burns. (25 hp burns 2.5 GPH WOT). less at lower positions, all depending on the boat and load.
Yamaha puts out some MPH, GPH, and MPG info for different motors and boat set ups

[bigfish1229]

All Small Yamaha Motors And Most Otehr 2 Cylinder Motors Are 100:1 Only When U Get About Say 30hp Does It Switch To 50:1

[99yam40]

I have run a '82 25 Johnson, '91 25 Evinrude, 1970's 15 Evinrude and even a older Sears 45 & 7.5 air cooled motor many years ago before I got this C40 Yamaha and they all were 50:1 .
You need to make sure your owners manual calls for the 100:1 before running it that way. 2 cycle motors will run on straight gas even, but not for long.

[robert graham]

I checked the Yamaha book and all 2 stroke motors frm 28HP and less are 100 to 1 ratio. All above 28HP are 50 to 1.

[99yam40]

What year models are we talking about? The only person I know personally that has a Yamaha smaller than a 28 hp has a middle 80's 20 or 25 model and I will have to ask him what he runs in it next time I see him and then ask if he has a manual for it.

[robert graham]

In the back of the 2009 Yamaha Outboard Motor catalog it has a 2 page fold out giving all the specifications on each motor in their line. It says 100:1 for the 28HP and lower motors. I gotta believe Yamaha couldn't afford a misprint on a critical item like that. Good Luck!

[99yam40]

I am sorry if I made you think I meant it was not correct , I was just asking what all year models use the 100-1 or when they started that.
Was It back in the 80's ,earlier, or later years?

[robert graham]

I can't really say about the older water cooled motors but if I had one, I'd sure check it out to be sure about the ratio. I still run an old 3HP Tanaka air cooled on my canoe but it's got the mixture right on motor,50:1. I'm pretty sure my blower and weedeater use a 32:1 Good Luck!