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What do you guys with two strokes run for fuel (octane rating)? My motor is a 1978 Mercury 80 hp.

I was advised by local marina to use only 87 octane. They said not use the higher octane rated fuels due to too much detergent. They said timing would be off with said fuel. I've always used premium gas but since switching to 87 octane, I've noticed no difference. What are your thoughts?

Thanks, Dave

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My school of thought is that it's a 2-stroke "Low Compression" engine and should be run on 87 octane. I use 87 octane, measure the "EXACT" amt. of O.E.M. 2- stroke oil, and 1 oz. of "Sea Foam" fuel additive per gallon of fuel. My engine fires right up every time. Sea Foam is well worth the few extra "clams".

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matt i run marine stabil every tank, sea foam once in awhile to decarb ect.{ great stuff for sure} motor starts and runs great .i was having a minor hesitation problem all you guys recommended sea foam.....you were right. just wondered if you all think higher octane is a bad , neutral, or .good idea. thanks again dave

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I use 87 octane fuel.

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I recommend using whatever fuel type is recommended by your outboard's manufacturer.

I use 87 Octane fuel with my Mercury two strokes.

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I also use 87 octane in my Johnson 2 stroke. Everytime I fill the tank I too put in a few ounces of Sea Foam. If you have the manual for your engine put the octane in that is recommended. I was told also that two strokes don't like all of the detergents in higher grade gasoline and also that these engines are sold all over the planet and in alot of third world countries they don't get different grades of fuel. Probably lucky they get 87 0ctane at all. Also in times of no use fill your tank all the way,add Stabil and you should not get any or very little condensation in the tank. Good Luck!

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I was having fuel issues as well and i used stabil and seafoam but this last time i was recommended to try startron anybody used it before it seem to run really good.

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As far as Mercury goes, 87 octane is recommended in all outboards except 275 and up Verado's then it's 92 octane. We are also recommending startron.

Honestly, when 75% of my work orders are for carb problems related to debris, the best defense I've found is "RUN YOUR ENGINE". I have a friend with a 2007 225 Verado with over 1200 hours and he's never had a fuel problem or any other that I'm aware of. If you're not running your engine at least 30 minutes every week, standby for fuel issues. IMHO If your not taking the boat out, hook up the hose, get a cup of coffee and let the thing run in the driveway. Trust me, the whole "Low Hours" thing is a downfall now.

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Fuel addatives... pick your snake oil. With all the talk throughout the years does anyone actually know of any unbiased scientific reports on the popular additives?

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There is a question sure to stir all sorts of discussion.

I'll ad my 2 cents. D Winter just said most of what is needed to be said above. Running an engine on a fairly regular basis is probably the single best thing we can do for them. Gasoline looses it's freshness and hence it's octane fairly quick and I have my doubts it is actually 87 or 89 the day you buy it at the pump. I use Stabil in all my tanked fuels and I try not to keep fuel in tanks for over 3 months. If you have 2 tanks, run one out and switch to the other and run it out. Nothing is better than fresh fuel and if you can avoid the ethanol in your area I would highly recommend doing so.

Fuel additives have been around a long time and I have never seen a comprehensive study proving they have any value but we have all heard from many who swear by their particular brand. I also don't believe much of the hype regarding the various oil brands. Use the one you like or trust but just because it has a particular brand label tells us very little about what is actually in the bottle or what refinery made it. As long as the oil you use has the correct designation numbers it should be perfectly fine and none of these companies can prove their oil is any better then the other brands.

Gary

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Ask your Engine dealer about adding a carbon guard to today's fuel, and see what he says...

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Gasoline with ethanol, E10, is said to be expired after 90 days. Alcohol attracts moisture and it is this attracted moisture that causes the issues. There is no additives that can stop the alcohol from attracting moisture and therefore there is no better alternative than burning the fuel you buy and keeping the tanks fresh.

There are numerous articles written about ethanol but nothing I have read ever mentions a way to keep E10 fuel fresh other than burning it in a few months. Ethanol can attack the rubber compounds in your hoses and fuel lines and also the O rings in your fuel system and the plastics and fiberglass in your fuel tanks. Nothing you can ad can stop this.

We can buy water separators and additives but nothing is better than keeping fresh E10 fuel in your tanks and using it all before refilling the tanks. If you can still by straight gasoline with no ethanol you are well advised to do so as it has a much longer shelf life.