What grade gasoline to run?

[John Ramstead]

Would like some feedback on what grade gasoline you guys run.
I run unleaded plus. I know when i run premium unleaded in my
car i get better gas mileage. But i've also heard premium unleaded is not good for boat motors, I run a 50/35 Yamaha Jet.
Thanks for the input.

[REW]

Many of todays fuels - especially the ones containing alcohl tend to be a bit on the dry side. that is why many of the motor manufacturers recommend running the fuels of 92 octane. These fuels tend to contain more of the cleaners that are necessary for long term motor operation --- or so I have been told by many different mechanics.

I have found that by running the higher octane fuels - by myself and my friends, that we have considerably better starting and idling motors. When you troll for many hours at a time -- it is very nice to be able to have a motor troll at 400-500 rpm without fouling plugs etc. the higher octane fuels seem to solve this problem.

I haven't noticed any particular difference in top end or mid-range.

Take care

REW

[EAGLE EYES]

You'll want to run premium everytime can. But one thing to look out for with premium fuel, is the unclearly marked pumps. Some premium fuels contain Methanol and or Ethanol both are terrible on two stroke motors. These two products will cause a slow build up of un burned by-product in your jet system. This leads to a lean burning engine which causes excess internal heat, possibly scoring pistons and other combustion chamber problems. Premium fuel (92 Octane) that is clearly marked nonoxygenated is what you'll want to look for.

[mbrandt]

Does this only apply just to the larger horsepowers or is this valid for all 2 stroke engines? How about the ones where your still mixing oil into the gas.

Thanks,

Mark

[REW]

I run premium in all my engines - except for "standard" auto engines.

i.e. lawn mower, chain saw, small 2-stroke outboards, large 2-stroke outboards, snowmobile and motor cycle.

Works great for all of them.

Take care

REW

[horkonwall]

I spoke to Jay Anderson from Mercury about this this summer. He recommended to run regular fuel with TCW3 oil. This oil is manufactured to compensate for low octane. The exeption was for high altitudes like Fort Peck Mo. to run premium to compensate. Also buy your gas from high volume dealers to make sure it is fresh.

[vetspet(ind)]

i have heard that premium gas stores longer....otherwise no real benefits except what REW mentions about cleaners

[EAGLE EYES]

Horkonwall made a good point about the what type of oil you run! Even though you can get by with lesser octane fuels, You will notice a difference in how 2 strokes run. Premium fuel(92 Octane) is more explosive than 87 Octane plain and simple. When your running a 2 stroke engine the oil must lube and burn equally. Premium gasoline will get the job done! It burns cleaner, less carbon build up and high output firing, make for a smooth running engine.

[eley]

I would refer you to an article written by Jim Barron in "Bass & Walleye boats" magazine, I am not sure of the issue but he contacted all of the outboard manufacturers for their recommendations on octane to run in their motors. Yamaha said premium fuel is OK but not required. Merc states that premium fuel is preferred and that their engines run stronger & cleaner on premium fuels. OMC states oxygenates in reformulated gas cause engines to run lean and hot, premium fuels have more oxygenates, avoid premium fuels. I think some of the other guys said to make sure you use a high quality oil and I think that is important, I always use OMC or Merc oil

[Dan]

Not all premium fuels contain oxygenates.(Ethanol)See eagle eyes' post. Also, higher octane fuels do not give you more punch or more power. Octane is relevant only to the speed as to which a fuel burns. 91 octane burns faster than 87. This is why you see better starting better idling when using a higher octane fuel.The only time I run 87 non-oxy fuel in my Mercs is when 91 non-oxygentated fuel is not available.

[Sandman]

After that article ran in Bass and Walleye magazine I called the merc factory rep, since my manual said use 87 octane, and the rep said the article was wrong and that they do not recommend anything above 87. It is my understanding that higher octane fuel breaks down faster during storage--true or not. Buy your gas at a station that sells large quantities of gas so it doesnt have a chance to sit in their tanks. Higer octane gas usually doesnt sell as fast and usually sits in their tanks longer. I have run 87 in my 115 carb Mariner for four years with no problems. I do add Merc treatment in the cold weather and during long periods of storage. One ounce for every two gallons. This gas thing is really confusing!!!!

[Al Gore]

I sponsored a bill that enacted legislation to create Unleaded Gas. I also coined the phrase Internal combustion engine. Add to that I invented Yamaha and my mother used to sing Too Drunk to F*** to me as a nursery rhyme.