# Question about a 100:1 oil ratio



## scoobeb (Nov 10, 2011)

Hey fellows this is not a debate of what is right and wrong it's just simply a question about a 100:1 oil ratio for a 15hp 2stroke yamaha or any smaller outboard that may call for a 100:1 oil ratio.

My question is has anyone ever heard or experienced a motor with problems or locking up from a 100:1 oil ratio when they were using it full time?I know that johnson and evinrude changed it yrs ago from 100:1 to 50:1 because when the motors sat for a long peroid of time there wouldn't be proper lubrication sitting in the engine and would cause corrosion or the motor would seize up.

I'm talking about a motor that will not sit for longer then like 2weeks at the very most if that.I will probally use it at least once to twice a week.I'm not asking if it is the right ratio as i know everyone has their opinions on that,i'm asking for anyone who has actually uses their motors full time,has never let it sit for a long peroid of time.Has anyones motor seized up at all or given them any problems at all that they know of from a 100:1 oil ratio?Thanks.


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## Pappy (Nov 10, 2011)

Okay, lets try this again another way. 
In a perfect world and under perfect conditions your 100:1 ratio will be okay to run, that is what you want to hear? That is the world these guidelines were made up in. Now, welcome to the real world where things happen a little differently.
Fact is that your engine is not made of anything different than the Johnsons and Evinrudes and will go through the same issues eventually.
Another fact - two strokes never die of too much lubrication, period....... The reverse is not true. 
The extra lubrication of going to 50:1 will help protect you through the inevitable overheat you will experience. Extra lubrication will help out the engine during periods of light detonation should that occur from a load of bad gasoline or a failing ignition component. When your waterpump is partially blocked or old and worn and the engine is running warmer than designed yet not overheating, you will be better protected. Threre are a few other scenarios I can think of as well. 
Extra lubrication will reduce overall wear and either bring down or maintain internal rotating parts temperatures in a two stroke better than a lean mixture.
Yamaha parts are outrageously expensive and two strokes are no longer manufactured so I for one am protecting my fleet of them the best way I know how to. Quit wringing your hands over a little extra oil!!


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## scoobeb (Nov 10, 2011)

I don't understand why you think this is about extra oil or anything else.I asked a question if anyone has had a engine failure from running an outboard on a 100:1 oil ratio.That is all i asked.I said in the post this is not a debate on what oil ratio is right.I want to know if anyone here that owned a motor has ever had a engine failure,nothing else.I am going to run my engine at 50:1 no matter what the answers are.

I am just curious if the oil ratio of 100:1 has ever failed anyone.


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## LonLB (Nov 10, 2011)

scoobeb said:


> I don't understand why you think this is about extra oil or anything else.I asked a question if anyone has had a engine failure from running an outboard on a 100:1 oil ratio.That is all i asked.I said in the post this is not a debate on what oil ratio is right.I want to know if anyone here that owned a motor has ever had a engine failure,nothing else.I am going to run my engine at 50:1 no matter what the answers are.
> 
> I am just curious if the oil ratio of 100:1 has ever failed anyone.




You'll probably get answers about tons of them. But like so many other things, it'll be a guy I know, he knew this guy, who's brother in law knew a guy who read on the internet once that his brothers engine failed.


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## jspansel (Nov 11, 2011)

Guy I know, he knew this guy, who's brother in law knew a guy who read on the internet once that his brothers engine failed.

Oh! Looks like LonLB knows him too! :lol:


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## sixgun86 (Nov 11, 2011)

I've never had any issues running them a bit rich. From starting out with an older omc 100:1 motor and later going to 50:1 on newer motors I've always added a bit more to be on the safe side. In regards to not running to motor over extended period of times I'd always at least pull it a couple times when I was in the garage. Had a OMC 6hp in the family for 30yrs and just this season replaced the powerhead b/c it had locked up.


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## Captain Ahab (Nov 12, 2011)

So if the answer is yes - my motor seized from running too lean what (or how) would that help or hurt? (gotta love the answer the question with a question game).


Why are you asking?


And yes, I have seen 2 stoke engines that have seized 9or otherwise failed) from too little oil

Changing a fouled plug once in a while is better then changing a seized power head


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## scoobeb (Nov 12, 2011)

The thing is everyone seems to think that the 100:1 mix was for emission reasons.The thing is yamaha has had all their pre mix 2strokes run on a lean mix of 100:1 for a long time well before any of this emission stuff came into play.

So why would a engine manufacturer suggest a 100:1 oil ratio and it not be safe?Makes 100% no sense to me.It's funny when people ask any other question but oil related questions,everyone says follow the manual to the t,when it comes to a 100:1 oil ratio which yamaha says to do as the manual says no one feels or questions yamaha knows what their doing in that one area for some reason so this has peeked my interest.

I can probally understand if an engine sits a long time a bit of extra oil will help lubricate it better and stop any corrosion i would think(please correct me if i'm wrong here).I will use this motor full time also as i stated in my earlier post so it will never sit for longer then lioke 2weeks give or take a bit.Also is there any advantages from more oil then the motor calls for besides the extra lubrication in the engine?Like more power or not,better fuel economy or less,just some examples like that.What are the pros and cons of less or more oil if there is any besides the extra lubrication?

I don't think anyone is right or wrong here,i just wanted to know if anyone has run a yamaha or any motor that calls for a 100:1 oil pre mix and has had a engine failure do to being to lean.A ton of people say that johnson evinrude went back to a 50:1 oil mix for the reason i stated in my earleir post,lack of lubrication or corrosion from sitting in storage for a long peroid of time with no oil to cover the internal parts or somewere along that line.I have heard from so many people who argue(no related to this site)about doing everything by the book.Everyone says who knows the engine better then the people who build it right?So for the life of me why follow everything by the book but the oil ratio?That is what i'm trying to understand.

I'm running a 25:1 oil ratio on my break in of my yamaha and it runs like a champ,a hair bit of a rough idle and a ton of smoke but it starts up on one pull and runs awesome.I mean going from 50:1 to a 100:1 after breakin is a big oil difference.In a 3gallon tank that either 8oz of oil or 4oz of oil.If yamaha knows this would hurt their motors why would they continue to leave it that way for a ton of yrs.This is not an issue of where i'm trying to be cheap and save on oil i'm just trying to really understand this theory.I'm not trying to debate anyone,just want to learn thats all.Thanks guys.


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## PSG-1 (Nov 12, 2011)

The only disadvantage of running the fuel mixture richer is that the engine will tend to foul plugs at idle. 

BUT, it will sure keep away the mosquitoes and no-see-ums!


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## Captain Ahab (Nov 12, 2011)

If your Yamaha calls for 100 to 1 then I would do that - there are afew other variables such as RPM range, how much spark you get, your type of fuel delivery system, etc.

Perhaps your Yama carbons up easily or something? Have you asked Yamaha?


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## G Lap (Nov 12, 2011)

I have a 1987 two-stroke Suzuki 20HP outboard that calls for a 100:1 ratio of oil to fuel. The motor I had before that was a 1967 Johnson 33hp which called for a lot more oil in the mix. When I got the jon boat with the Suzuki, it sure didn't seem like much oil added at each fuel up . . . but I figured if that's what Suzuki called for, then that would be best. I fished with the Suzuki for about 8 years, sometimes a few times a week and sometimes with large spans between each use as much as 10 months (too busy, away at work). I always mixed it 100:1 and never had any types of problems. I agree that is doesnt seem like enough lubrication for the cylinders, but they must have designed it that way for a reason. I just got a 1994 25hp Evinrude, so I will probably sell the Suzuki . . . but it sure was a dependable motor.


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## bcbouy (Nov 12, 2011)

i have a 15hp 2 stroke yamaha that i run @100:1 using yamalube synthetic,like the man. recomends.it isn't always 100:1 because i don't always run the tank dry.so the mix is between 100 and 90:1.as for motors sitting,they sit for a while at the dealers,and mine is in a heated garage.i trust the manufacturer to not steer me wrong on mix ratio because a blown head after a year or 2 is not very good for buisiness or repeat customers.maybe after a few hundred hours i might mix 80:1 but thats a long way off.


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## knnymain (Nov 13, 2011)

Ive had my yamaha 25 since new in 93. I have always used 100 to 1 and occasionally added a little extraoil to the mix. ive also ran my boat almost continuously a couple of times burning up a 6 gal. tank in the process. and am glad to say ive never had any siezing problems. matter of fact i still have split fire plugs that are at least 8 or10 yrs old YAMAHAS ARE GREAT MOTORS


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## Sasquatch (Dec 14, 2011)

This being my first post here, I'll openly admit that most of my experience with boats is not in the form of outboard motors. That said...

For trolling I run a 1983 Yamaha 2hp (2B). 

History of this motor: This past summer before I found a larger motor I (that could actually afford) I put probably 200-250 hours on the Yamaha in fresh water here in Colorado. Prior to that it spent 10 years in my dad's garage before he gave it to me. Prior to that it had a hundred or so hours put on it in fresh water in the U.P. of Michigan and before that, when it was used regularly by my father, it got a few hundred+ hours in salt water when he lived in Florida. During it's entire life it has been run on the manufactures recommended 100:1 gas/oil mix using their brand; Yamalube. 

Problems I have noted: It didn't just start right up when I got it. I had to clean out the fuel lines, since then it's run like a champ. Clearly this was to be expected. 

The one other problem I have noted with this particular motor is that if it's not running and you pull the prop up out of the water for any reason with the fuel line open it will flood the carb really badly. Takes about 30 minutes to clear the carb, but then it goes back to running really really well. 

My view on this is that a prior poster is probably right, the manufacturer is giving you the correct gas to oil mixture for the way your motor was designed. But I will attempt to locate my owners manual and see if it elaborates on this topic. Further, I would say that a little extra lubrication probably won't hurt the motor though it will foul your spark plug faster. That said, it's probably not any "better" to run it richer than it was designed for either.

Will advise when I have manual in hand.


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## Sasquatch (Dec 14, 2011)

Shockingly, the manual was where I expected it to be. So this is the one instance where I should have looked before posting lol. 

Instructions from Yamaha are as follows: 

Break-In Period: 25:1
After Break-In: 100:1.

The manual notes that less than 100:1 will cause the engine to seize eventually, while running a richer than recommended will result in "Fouled spark plug, smoky exhaust or heavy carbon deposits..."

To find your specific manual try this website: https://www.yamahaownershandbook.com.au/

Cheers!


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## scoobeb (Dec 17, 2011)

Well i forgot to mention something.I also use full synthetic oil from amsoil as of now but i'm thinking of going to the xd100 oil from evinrude.From what i understand it protects and lubricates better then regular mineral oil.I would guess even though i'm using way less oil as far as 100:1 or even a 50:1 as i'm running now it will protect better with less oil.

See the thing is you can buy a new etec and they have 3 settings for oil and one is a 100:1 as this motor is.I know i know were talking way better technology and probally better built engines(etec)but yamaha can hold their own.I am running a 25:1 now but i'm just about done with breakin.I'm not oing a 10hr breakin as it's not going to make a difference as far as 5hr to 10hr.Pappy brought up a good point in another thread,he said that the motor i have is built like motors of yrs ago as far as materials there made of.

I have a few manuals fromlike the early 80's and the early 90's of yamaha and merc and in every one of those manuals of the merc ones it states only a 1hr breakin.What is different between the motors of today and then and the answer is nothing i would think so why should we break our motors in for 9hrs more then they really need.I know this is off the subject a little.I think 5hrs is way more then enough time.I have ran 4 times the oil for breakin as yamaha says to at 25:1 so i'm pretty sure in 5hrs every milk and cranny of this engine is lubricated pretty well.I'm going to change the spark plugs and lower unit oil before this next trip.

Then run it for another 15hr and then change the lower unit oil one more time just to make sure all the metal shavings are completely out.I would assume it wouldn't hurt even if i didn't change the lower unit oil at all but just for my own protection a fresh lube job won't hurt.I have brought this up before with the etec as you don't touch the lower unit for 3yrs from the time you start using it so what ever metal shavings are in their must work their way out.


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## turbotodd (Dec 25, 2011)

There is a such thing as "over oiling". Over oiling causes poor running, carbon buildup, fouling, ring sticking, port plugging in extreme cases. Yamaha designed their engines (40 HP and under for the most part) to run at 100:1. Their carburetors are jetted for 100:1. That means running 50:1 not only increases carbon and plug fouling, it also means that since there is twice as much oil in the fuel, some fuel is displaced, which actually runs the engine leaner (fuel/air mixture), and if you plan on running your engine at 50:1, they also recommend increasing the main jet about 5 sizes. BTW that's right out of a factory technical adviser's (RTA's) mouth. 

Folks don't really think much about running 50:1 but without modifications, it does reduce engine life if the engine's designed to run 100:1. Keep in mind with a 4 stroke engine, we have the cool incoming air/fuel charge on the intake stroke to cool the piston tops, combustion chambers, spark plugs, and cylinder. With a 2 stroke, we don't have that incoming charge cooling nearly as much. The piston rings are the major component that will dissipate combustion heat from the hot piston to the liquid cooled cylinder wall. Also remember on a 2 stroke, we have a power stroke every revolution which also reduces cooling. That's why most air cooled 2 strokes have bigger fins than a 4 stroke does. The extra oil due to running 50:1 results in carbon buildup, which cokes the rings and makes them stick. Also cokes the top of the piston, the bottom of the combustion chamber as well. When the rings gum and stick we lose cooling performance, same with carbon buildup on piston tops and combustion chambers. That's why Yamaha designed Ring Free fuel additive-to clean excess carbon from the engine. And that stuff flat out works!

Now you guys with DI engines (direct injection 2 strokes), you don't have ANY fuel in the incoming charge (only air) which complicates things even more. In the case if DI engines, you MUST have zero carbon on the pistons and rings, if there is any, it will start the failure process--and that's why the manufacturers of those engines require their own recommended oils. It's also why FICHT from Mercury was a flop. Good throttle response and they idled good but they never seemed to last long.

That said, the only failures I've seen from too much oil are loss of compression (stuck rings) and in one case, a failed crankshaft seal...but that seal was so destroyed that it made it hard to say whether excess oil caused it or if it was a case of severe engine abuse...and in all honesty, judging by the looks of that particular motor, it was probably the latter


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