Yamaha outboard oil mix.

[ianmkent]

I recently brought myself a used yamaha outboard but, I am a little bit confused about the fuel mix. It states 100:1 on it is this 100 parts fuel to 1 part oil? It seems to be a rich mix in my opion would a 1:50 mix be beter? What do you guys recomend. Its a blue outboard from the late eighties.

 

[lydiamight]

If it's a smallish outboard and blue in colour it might be a Yamaha Malta 3hp. Still got one in the shed, always started easily and having a neutral and forward position on the gear lever was much better than the old "pull to start and your'e off" system that seemed to be so popular with small outboards of that era.
Although 100:1 was the recommended fuel mix I preferred to use 50:1 to make sure that the engine didn't seize when worked to hard.
A 50:1 mix didn't seem to coke it up either providing you used a good quality two stroke oil.

 

[VicS]

I recently brought myself a used yamaha outboard but, I am a little bit confused about the fuel mix. It states 100:1 on it is this 100 parts fuel to 1 part oil? It seems to be a rich mix in my opion would a 1:50 mix be beter? What do you guys recomend. Its a blue outboard from the late eighties.

100: 1 is not a "rich" mix . Its about the lowest proportion of oil in petrol that you would get away with. Its only 1% oil.

50:1 contains twice as much oil ( 2%). Most 2 stroke outboards used 50:1 from about 1970 onwards. Before that they used even more oil.

I would run it on 50:1 unless it caused any problems, in which case I'd go somewhere in between. Very probably 50:1 was recommended for the first few tank fulls when new

Although recreational engines may have used 100:1, 50:1 was usually recommended for commercial use.

If you do run on 100:1 add a bit more oil to the last tankful before laying up, or "fog" the engine immediately before storage.

 

[boatingdave]

100: 1 is not a "rich" mix . Its about the lowest proportion of oil in petrol that you would get away with. Its only 1% oil.

50:1 contains twice as much oil ( 2%). Most 2 stroke outboards used 50:1 from about 1970 onwards. Before that they used even more oil.

I would run it on 50:1 unless it caused any problems, in which case I'd go somewhere in between. Very probably 50:1 was recommended for the first few tank fulls when new

Although recreational engines may have used 100:1, 50:1 was usually recommended for commercial use.

If you do run on 100:1 add a bit more oil to the last tankful before laying up, or "fog" the engine immediately before storage.

+1. Been investigating outboards for some time and done loads of homework. Very sound advice.

 

[Prhperio]

I recently brought myself a used yamaha outboard but, I am a little bit confused about the fuel mix. It states 100:1 on it is this 100 parts fuel to 1 part oil? It seems to be a rich mix in my opion would a 1:50 mix be beter? What do you guys recomend. Its a blue outboard from the late eighties.

YMMV but personally I'd use 50:1 Those who know better than me always seem to say that 100:1 was so much advertising puff and might result in insufficient lubrication, especially if run hard. I used to buy outboards from an outfit run by an ex powerboat racer and the 50:1 mix "even" for recreational use was always recommended even if the manufacturer suggested 100:1

 

[landlockedpirate]

I have watched these threads for years about running Yamaha's on 50:1, but I dont get it.

We have had Yamaha's since 1981, everything from 2hp to 90hp, about 20 in total.I have run every single one of them on 100:1 (except for the running in period), exactly like it says in the hand books. Every one of them has been superb, no issues at all,so why run them at 50:1 ? And especially when we kids, these engines were run flat out for hours on end !

It seems to be asking for trouble, it will lead to oiling of the plugs, huge amounts of smoke and a virtual oil slick behond you.

 

[VicS]

I have watched these threads for years about running Yamaha's on 50:1, but I dont get it.


It seems to be asking for trouble, it will lead to oiling of the plugs, huge amounts of smoke and a virtual oil slick behond you.

What rubbish. Most other brands of two stroke outboard use 50:1

 

[Questor]

It seems to be asking for trouble, it will lead to oiling of the plugs, huge amounts of smoke and a virtual oil slick behond you.

When I bought mine, dealer said run it permanently on 50:1, even though book says 100:1.

I always have, and 11 years later, never have had a problem.

Only changed the plugs once in that time. No fouling, no oil slicks, only a little smoke on startup, but it does smell good.

 

[landlockedpirate]

But you are all missing the point, why would a global company with turn over in the Billions and 1000's and 1000's of outboards sold all over the world tell us to run the engines on 100:1 if in fact they should really be run on 50:1 ?!?

Imagine the number of failures and warranty claims they would get !

Although you dont notice the oil slick, try running the engine in a bin on 50:1 for even a few seconds, the mess it makes is massive.

 

[Montemar]

I have the Yamaha Malta and a great engine it is too. I run 100:1 as that is what Yamaha recommend - why would I not do what the designer and manufacturer says? 50:1 smacks of paranoia!
I have an old Avon Redcrest 2.8m dinghy that the engine pushes along rather slowly and when the wind from astern is moving faster than the dinghy you sit in a haze of 2-stroke stink and SWMBO don't like it! This would be worse with 50:1 wouldn't it?

 

[mikhalis]

Had a 5hp 2003 Yam 2 stroke from new and the dealer advised me to do 20hrs run-in at 50:1 and then 100:1. Bought a secondhand 8hp c.1998 a few years ago and I run this at 100:1, as it says on the side, with no problems. Main thing is making sure that I keep the tanks for the 10:1 seagull and for the 100:1 Yam well marked.

 

[Monique]

My brand new (not yet broken in)(got very lucky) 2011 15 HP 2 STR Enduro is getting 25:1 during breaking and will get 50:1 afterwards.

As per the Yammy Manual.

 

[Racingfrank7]

Run my yams on 100:1 like the book and sticker says with no probs.
As for people running there 100:1 yams on 50:1 mix as you think it's safer then just have a think about this .......

In simple terms

The jet being a fixed size, will allow set amount of fluid through. If you mix oil into the petrol then the % of petrol in that fluid is reduced from 100% to 97% ish on a 30:1 mix. (30 parts petrol to 1 of oil) So less fuel in, hence a leaner mixture. Having said that if you increase the jet size by 3% to compensate that takes a 270 main jet up to 280 to the nearest jet size

Get it ?

 

[Greg2]

The manual for our Yamaha outboard says 100:1 so that is what it gets. Even then it is a bit smokey but it runs fine. I am in the 'do as the book says' camp.....can't see why I wouldn't follow the manufacturers recommendations but could be persuaded if there is a sound engineering based reason as opposed to opinion and scuttlebutt

 

[No Regrets]

Some manufacturers tried 100:1 and dropped it a year or two later. I presume they had failures in the case of engines used hard.

Also, some people underestimate the amount of two stroke the pour in wantonly. 50:1 still gives a safety margin in these cases!

 

[steve66]

Run my yams on 100:1 like the book and sticker says with no probs.
As for people running there 100:1 yams on 50:1 mix as you think it's safer then just have a think about this .......

In simple terms

The jet being a fixed size, will allow set amount of fluid through. If you mix oil into the petrol then the % of petrol in that fluid is reduced from 100% to 97% ish on a 30:1 mix. (30 parts petrol to 1 of oil) So less fuel in, hence a leaner mixture. Having said that if you increase the jet size by 3% to compensate that takes a 270 main jet up to 280 to the nearest jet size

Get it ?

Quite correct on a brand new carburettor, but what you may not have considered is jet wear. On a used second hand outboard thats a few years old you wont notice a difference. I always suggest running at 50/1. I crtainly aren't going to argue with manufacturers but i just get worried running at 100/1

 

[steve66]

Hi Montemar, at 100/1 you shouldnt notice any 2 stroke haze at all. You may get a slight smell but definately no smoke. Are you using outboard 2 stroke oil as opposed to standard off the shelf 2 stroke oil?

 

[Sandro]

Following my feelings (I have also an old Seagull) I totally agree with VicS and would use at least 2% (50:1) oil, which in my opinion would lengthen the engine life, but:

1) What Racingfrank7 says is true: same air intake, same jet, more oil, less petrol, mixture leaner than designed.

2) I have a Johnson 4 hp of 1984 rated for 2% mix by the manufacturer. When it was brand new, also after running in period, I always used 4% (25:1), just because of my feelings of an old man.The motor never ran well, sometime I had to keep the choke half closed to keep it going. Then someone told me to try and use the prescripted 2% mix and since then it ran well.

3) John Williams of SOS says that if you want to run a Seagull to less oil you can, but must change the jet to a SMALLER one.

4) The manufacturer instructions are Bible to me.

Now, reading that many are happy using twice the oil percentage - as I too would like - I am confused.

Any explanation? Am I missing something?

Sandro

 

[Montemar]

Hi Montemar, at 100/1 you shouldnt notice any 2 stroke haze at all. You may get a slight smell but definately no smoke. Are you using outboard 2 stroke oil as opposed to standard off the shelf 2 stroke oil?

Thanks, the haze is invisible but the smell is real. As I bought the engine secondhand with a few litres of 2-stroke from an expat in Spain the oil could have been anything! When I mix up another batch with proper oil I expect I will find out.

 

[ontheplane]

I've had many Yammies - always run 100:1 - always been perfect.

When I've run richer (pre-winterisation or post) they run smokey and not very well - as soon as I've run an hr and put it back to 100:1 they run fine - so I'd stick with the proper mix if I were you.