2 Stroke Oil Mix

[UFO]

I have a 2 Stroke Yamaha 15HP Enduro (Just found out its a 2016 model).


Just brought it home to do a Carby service as its running a little rough and pulled the plugs to find them oily (see pics).


Previous owner told me to use a 50:1 Mix - But Manual says 100:1 But many people on this forum espouse 50:1 - As its a 2016 model should I be going 100:1?



Is there anything else that could be causing the plugs to oil up or should I simply go to 100:1?

[Chotu]

Why don’t you give 75 to 1 shot for a little while?

[a64pilot]

I’d stay at 50 to 1. Is the plug actually fouled or just oily? It doesn’t look fouled.
I’d suspect a rich fuel mixture and that of course will bring in more oil along with the increased fuel, good news is that no two stroke was ever hurt with a rich mix, it could just be you need to do an Italian tune up more frequently.
100 to 1 is done for reduced emissions, it’s not that the motor needs it or will foul plugs etc, it’s that the motor will have reduced emissions if you use half the oil.
It will tolerate it obviously but in my opinion at an increased wear rate.
Back in the day 25 to 1 wasn’t uncommon and 50 to 1 is actually pretty lean.

However having said all of that if your engine spends its life at low RPM and loads, then 100 to 1 will be fine.
The last days of most two strokes they had variable rate injection and at low loads they would inject extremely lean oil mixes, down well less than 100 to 1, but as you ran it harder, the amount of oil would increase drastically.
Pre-mix is of course not variable and sort of a mix it the strongest, that way your covered at WOT.
I haven’t had a two stroke in a coons age, but I believe the Enduro models spec 50 to 1 and it’s only the leisure models that are 100 to 1, and I believe that reflects the intended use model, Enduro’s are expected to be run hard and run often accumulating a lot of hours on commercial boats, Leisure models only on some weekends on pleasure boats.
It’s not that the Leisure models are built better or out of superior metals or superior design.

So in my opinion 50 to 1 is best for the motor, but it significantly increases pollution, 100 to 1 will cause more wear, but burning half the oil reduces pollution. I guess it depends on how environmental you are, but if you are, get a good fuel injected four stroke, I bet it takes 10 of them to pollute as much as one two stroke.

[Sailmonkey]

I vote for leave it at 50:1 and run it hard.

We’ve got a little 5hp 2-stroke on a small dinghy that won’t plane with 2 people in it. I run it 50:1, run it hard to make a hole in the water, and have never had a problem with oiling of the plug.

[DougR]

Well, you could run the manufacturer’s recommended oil, the recommended oil mixture ratio, and the recommended spark plug heat range, but then, what does the manufacturer know?

Probably nowhere near as much as the prior owner and everyone else.....

[anacapaisland42]

I've run my 1984 Yamaha 9.9 2 stroke on AMSOil 50:1 mixture from day 1. The only repair in 36 odd years has been one impeller replacement. It gets new spark plugs, let me see, I guess every 10 years. It has done thousands of miles double duty as the main propulsion on our 32 foot sailboat plus the main propulsion on our 16 foot heavy metal fishing boat plus as the main propulsion on our 2 RIBBY's. It spent one winter frozen in when I broke my leg and couldn't get it out of the water.
So....for my $ 50:1 AMSOIL ......with whom I have no connection other than being a happy customer.
Bill




Previous owner told me to use a 50:1 Mix - But Manual says 100:1 But many people on this forum espouse 50:1 - As its a 2016 model should I be going 100:1?

[khoff]

I am in the 50:1 crowd , engine lube is not where you skimp !

[Mazu]

I have a 1986 15 Enduro and run 50:1. No issues at all with the engine. I had to replace the steel tilt bar with the aluminum upgrade as it froze but you probably already have this upgrade. I bought my boat in Puerto Rico where I lived back in 2010. The Enduro 15 is a Caribbean motor. That was the target market and there are hundreds of these engines down there. Most of the engine failures I know of were from overheating due to a worn impeller. I change the impeller, zinc and lower end lube every year and I expect the motor will outlive me...
I did have a little low speed fouling of the plugs and would have to open up the throttle now and again but sometimes had to pull the plugs and clean them. When having the tilt bar replaced I brought this up to the dealer who suggested the next hottest plug. I switched plugs and never had a hesitation or stuttering problem again.

[Pete7]

Originally Posted by UFO

Just brought it home to do a Carby service as its running a little rough and pulled the plugs to find them oily (see pics).

Just before the engine was shut down for the last time before the plugs came out, was it being run slowly or idling for any length of time which might have caused it to oil up?

Pete

[letoile]

DougR, has it right with one qualification. The grade of 2cycle oil used is as important as the ratio. The 100/1 oil is engineered to run at that ratio , the same as my Stihl weed eater and Suzuki 2 stroke I use 40/1 oil and mix at that ratio. My Jonsered and Husqvarna chainsaws are 50/1 with Husky 50/1 oil but I run it 40/1 with my standardized Stihl 40/1 oil for simplicity sake. The Suzuki is 30 years old.
Thus you need to ensure the grade of 2cylce oil also. I never liked the sound of 100/1 ratio even with the 100/1 oil. I also mix a little richer and will put up with a little carbon build up and to save wear and tear on the engine. There is a downside of too rich a mix and that is a carbon built up on top of the cylinder that can actually cause premature firing when motors get hot( chainsaw).

[tangara]

You are taking of Yamaha engine the older models were 50 to 1 and the new models are 100 to 1 i don't believe these change were made whit-out intensive test. Excess of oil create carbon build up on piston seal ring.

[Vasco]

When the old 2 strokes were allowed in Canada Yamaha would call for a 100:1 mix in Canada. Buy the same engine in the Bahamas and it called for a 50:1 mix. I heard that the only reason they went to 100:1 was because of EPA rules. To the OP, are you running the right plugs? I always use NGK BR7HS-10. As to 2 stroke oil I always use TC-W3. And I always run them with 50:1 mix.

[onavegador]

I'm also part of the 50:1 community. If you like to use 100:1 you should or even must use the very expensive two stroke oil sold by the manufacturer of the outboard motor. With 50:1 I use a very common and cheap two stroke oil what is normally used for small motor bikes in France. Btw. if available my outboard runs on Ethanol free Gasoline available in the US in Marinas. My impression was that the motor runs smoother.



James
______________________________________


Florida in winter, Europe in summer

[BlackHeron]

That wet plug is from over-rich jetting, not too much lube oil.

100:1 is EPA emissions nonsense gobblygook from sruffed-shirt people who don't care one whit about how much life you ultimately get out of your engine as long as their negotiated air-quality limits stay under the numbers in their ledger books.. If people want to believe that 100:1 is enough for their engine's lubrication needs go right ahead. If it written down on paper it must be true, right? It's your engine to use and abuse as you see fit.

But the problem here is with your carb, not how much oil you are putting into your premix blend.

[Cheechako]

That plug looks rather typical for a 2 stroke really. They never appear dry to me. The good news is "Yeah, just mix it somewhere between 50:1 and 100:1" ! The plug in my Stihl Chainsaw looks that way mixed properly.

The bad news is the main bearings gave out on my old '94 Yam 15 hp after extensive use. So 50:1 may be better. Fortunately I got help replacing those bearings while in Trinidad from a cruiser ex OB mechanic! A few $ in parts and 1.5 hours.