Fuel/oil mix question

richnkay · Posted: Wed Mar 30, 2011 10:31 am Post subject: Fuel/oil mix question

I just got a 1989 Yamaha 6 HP (2 stroke) at such a great deal I couldn't pass it up, despite the EPA problems I might run into later at some locations. I will hang it off a bracket for use as an emergency kicker and also intend to use it to power a dingy at some point. My question is, Yamaha built the engine to use a 100:1 fuel oil mix. In doing some internet searching I find that some folks are saying a 50:1 mix is better and that is what they have been using in their original 100:1 recommended engines. Anyone with experience or knowledge on this? Right now I am thinking Yamaha built the engines and knows best, on the other hand it seems to be a mighty thin oil mix. Thanks,

Rich

thataway · Posted: Wed Mar 30, 2011 10:41 am Post subject:

I would probably go with the 100 to one mix, but it may call for specific Yamaha oil. If you use plain TWC-3 oil, you might be better off with 50 to one if the motor has higher hours (which you probably don't know). The down side of 50 to one might be more frequent fouling of plugs. But in a 2 stroke you generally end up changing the plugs more often than a 4 stroke any way.

Sounds like a great move, and an engine which will serve you well.

Matt Gurnsey · Posted: Wed Mar 30, 2011 11:59 am Post subject:

The 100 to 1 mix is adequate for an engine that is run regularly. During break in the engine needs 50 to 1, and our feeling is that engines used rarely should have 50 to 1 in them for proper lubrication.

Always use a good quality name brand oil.

richnkay · Posted: Wed Mar 30, 2011 7:04 pm Post subject:

Matt and Bob,

Thanks for the comments, gives me something to think about. I have ordered a Seloc rapair manual for it, there might be something in the manual concerning it also. I put a compression tester on the engine this afternoon, it seems to be as tight as the guy I got it from said it was, I think for as old as it is and as nice as it looks there are not a lot of hours on it. Anyway Kathie and I will feel a lot better with it hanging on the transom, "just in case".

Rich

Matt Gurnsey · Posted: Thu Mar 31, 2011 12:40 pm Post subject:

I would treat the engine as if it were brand new, and break it in according to the user manual, with 50 to 1 oil, and not a lot of high speed running for the first couple of hours.

Better to have too much oil than not enough when first starting out.

Have fun with the engine!

journey on · Posted: Thu Mar 31, 2011 1:44 pm Post subject:

That Yamaha has electronic ignition so fouling plugs is not a problem.

On my 2-stroke outboards, I always ran 50-1. The engines wore out from the outside (shift wearing out etc.) but never from the inside. 100-1 is fine, but I want to make sure everything goes right inside. I use 35-1 in the bike, works great there also. Oil's cheap, engines aren't.

By the way, they plate the rod bearings with silver to allow 100-1 ratios.

Boris

Larry H · Posted: Thu Mar 31, 2011 4:00 pm Post subject:

If you use the 100-1 ratio, the mix must be exact. There is little room for error at that ratio.

I would use 50-1 and follow the break-in instructions as posted above. Latter, you could cut the ratio to 75-1, or even the 100-1, but I would use the 50-1 ratio anyway. As posted, 'oil is cheap, engines aren't'.

If you use the 100-1 ratio, you should buy the Yamaha 100-1 oil.

Another reason to stay with 50-1 is that when storing or not using the motor, 50-1 will leave more oil on the internal engine components to protect against corrosion.

Larry H
Retired outboard mechanic.