50-1 mix virses 100-1 mix

[Jack in Alaska]

My main engine is a 55hp Yamaha 2 stroke using 50-1 mix.
I just purchased a 15hp Yamaha 2 stroke using 100-1 mix.
If I change the 15hp plugs to a hotter one can I use the 50-1 fuel from the big motor tanks without fouling the 15hp???

That would eliminate having two separate tanks/mix ratios.

[fiddlersgreen6]

Hi Jack--- I have found over the years, that in dealing with oil, motors & engines, you should stick with the factory recommendations. Years ago I use to mix one gt. of oil per 6 gal. tank, this was before there was a specific oil for outboards, some of these automobile oils worked fine and other brands were a constant source of problems and fouling, especially on my 50 hp. V- 4 -cylinder Evinrude. The 1967 manual for my Autin- Healey recommends 30W Castro oil, I found out the hard way by using different types & brands, as a result I'm back to Castro 20-50W. I also would check with more than one dealer/mechanic to get their opinions, as you know repairs for outboards are costly with lots of down time, waiting for parts. Sorry I couldn't be more helpful---Rich

[Larry H]

Jack,

Most likely the 15hp motor will run fine on the 50-1 mix. I would run the motor on the 50-1 and see if you get fouling. Changing the heat range of the spark plugs to a hotter plug can damage the pistions of 2-stroke motors. If you do go to a hotter plug, just go one step hotter, run the motor several hours, and check the plug. If the plug shows signs of being too hot, switch back to the factory recommended plug.

Larry H

Retired Evinrude/Johnson mechanic

[Kena B]

Jack,

I just sold my Lund Tyee (18 ft skiff) and it had a Yamaha (kicker)15 with 100 to 1 mix, and Johnson 115 horse VRO. I have trolled with the Yamaha for hundreds of hours and mixed 100/1 as recommended and ran like a top. I fished Petersburg and Wrangel for 10 years as well as Valdez, caught a bunch of fish. Bought it new in 1985 from Rocky's Marine in Petersburg. I did loan the boat to my son-inlaw last year and he had the only trouble I ever had with the kicker. Only to find out that he mixed 50/1. (He said it WOULD NOT START!!) I dumped out the mix and replaced with 100/1 and it started first pull (as usual) and ran it for 3 days trolling for silvers without missing a beat (as usual!!)

Stick with the 100/1 and enjoy. FYI: I always used the Yamaha 100/1 mix oil and had exception luck with it. Guess any oil may work fine but I tend to use what has proven itself to me in the past. Plus a small pint jug last all year!!

PS: That kicker will run all day on less than a few gallons of gas! Kinda hated to see it go but traded it for a new 25' CD!! My kicker now is twin Honda 90's!!!

Don

[rjmcnabb]

Hi Jack,
At least you have a simple conversion for your O/Bs: take a dip of 50:1 and add an equal amount of gas. For a Mercury 4 HP on my medium sailboat, at 50:1, my O/B guru said that I could run the engine at 150:1 as long as I kept the RPMs low. Good idea, but every once in a while I turn my wrist in the wrong direction so I let that idea go untested. Don't have the boat or the motor anymore, but that O/B was LESS trouble than the 4 HP Yamaha 4-cycle that I have now on another sloop of the same size.
Rod

[C-WEED]

I had a yami 15 h.p., 100:1 mix for 22 years on a 12 ft skiff. Sold the boat motor/trailer for $1500 after 22 years (when I got the dory) of economical fun. Never should have sold it...

Never a problem. Didn't even have to change the water pump or the rope start. The only thing that ever failed was the plastic nipple on the fuel filter cracked one time. And I had to use zip ties on the plug wires as they would vibrate off sometimes. I would stick with 100:1 mix. It was designed for that ratio. The extra smoke, pollution, reliability issues of 50:1 just isn't worth it. What a fantastic engine! Soon to be a classic when they finally outlaw the 2-cycle.