# 1985 Evinrude 6HP Yachtwin fuel/oil mix ratio?



## Tim Murphy (Sep 22, 2012)

Dear Board,

I'm going to go look at a used motor tomorrow to use as a kicker on my rig. If it checks out I'm planning on bringing it home. The seller says it's decaled with a fuel/oil ratio of 100:1 but as I research the engine on the internet I see information that says 50:1?

https://www.marineengine.com/boat-forum/showthread.php?220573-1986-Evinrude-6-HP-yachtwin-questions 

My question is will I hurt the engine if I run the 50:1 mix that I use for my 1982 Evinrude 35HP through the smaller motor? I'd rather not buy another tank and hose assembly if it can be avoided but I don't want to damage the smaller motor either.

Thanks in advance,

Tim Murphy


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## jasper60103 (Sep 22, 2012)

You should be fine running your motor at 50:1. OMC spec'd 100:1 on my '88 30 hp as well. They later reverted back to 50:1. The additional oil will actually protect the engine better.


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## Johny25 (Sep 23, 2012)

Yeah OMC recommended 100:1 from 1985-88 only to come out with a bulletin in Sept. of 1988 basically recanting the 100:1 recommendation and going back to 50:1. Your motor will run on 100:1 at idle or slow speeds without any issues at all. But if you run WOT for extended periods then this is where you can run into problems. 

50:1 will not hurt your motor and is better for it in the long run. I have still to this day have NEVER fouled a plug on any of the 3 motors I have from that era that recommend 100:1 and all I run is 50:1


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## Pappy (Sep 23, 2012)

Any 2-stroke engine can benefit from additional oil. 
Your engine can run on 24:1 all day every day without even thinking of fouling a plug should you want to go that far.
OMC went back to the 50:1 recommendation because of what was happening to the engines during periods of non-usage. Daily temperature changes built, trapped, and cycled moisture across every internal part on a routine basis. A 100:1 ratio offers little protection long term. This accelerated wear inside the engine. The ratio was changed back to 50:1 and the issue simply went away again. 
I routinely see Yamaha engines (that are currently run on 100:1) with light rusting on the crankshaft counterweights and rust marking on the rotating or bearing surfaces when we take them apart.......Not good!
I always run richer than a 50:1 ratio for the extra protection the engine will have if I block the water intakes and the engine overheats or something gets stuck in a high speed jet and the engine leans out. More protection is left internally as well during periods of non usage. Unless you are made of money and lack common sense (we love those customers), that added protection is worth its weight in gold.


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## Tim Murphy (Sep 23, 2012)

Dear Board,

Thanks for confirming what I thought about running the 50:1 through this little motor. Now I know I can run the same tank as my 35HP Evinrude, that will save the hassle of buying a new tank for 100:1 and remembering to swap them out when I want to or need to run the putt-putt motor.

Dear Pappy,

I have a 4 HP 2 stroke Yamaha that says to run 100:1 in it. If I'm reading what you wrote correctly I should just run 50:1 through it too, correct? That will save me more hassle and money because I'll just buy an extra fuel line with an OMC coupler for the tank and a Yamaha coupler for the engine and my one tank will be able to run all three motors. That's the kind of news I like to get! 

Thanks everyone for the help and advice.

Regards,

Tim Murphy


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## Pappy (Sep 23, 2012)

That is correct!
Happy to know you posess more common sense than money!......or at least as much.


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