New 115 Mercury

[snowfighter]

Bought a new outfit with a 115hp Mercury 4 stroke manual states regular gas wondering what others with same motor run regular or premium ?

[Kyhl]

Does the manual recommend a minimum octane rating and does it say anything about ethanol?

I would bet that regular would be fine since that is what it states.

I think the real question is to use ethanol or not. That depends on how long it sits. If the manual says ethanol is fine then ethanol would be ok as long as it doesn't sit for months at a time. Ethanol blends do not have a long shelf life.

[FM_Mike]

I have a 2011 Mercury 115hp. I have been running I guess what most people would call "Regular pump gas" I had no issues with it last year, and have run it for years in a smaller hp 4 stroke also with NO issues.

I use seafoam in EVERY tank and have for years. I also use the mercury products recommended to keep injectors clean and fuel fresh. I know this may be over kill, but since using I have not had an issue when my Merc 4 strokes in 10 years.

If you can find and want to use oxygenated gas many swear by it. As I said above I have had zero issues in 10 years with regular pump gas. One thing I always make sure of, when I put gas in the boat, I ALWAYS get the gas at a high traffic gas station. Fresher gas that has not sat in a tank like you may find in the smaller resort areas.

Hope that helps, Enjoy your new motor, I know I enjoy mine.

[snowfighter]

Thanks I was wondering what others used. The manual states 87% octane and I think it could have 5 or 10 % ethanol will have to double check. I asked because I had a 50hp 4stroke Honda before and the dealer said it run better on premium.

[reinhard1]

i have a 2002 Merc 115 4 stroke. i have used only premium non oxy. never had a problem with my motor. good luck.

[Down Deep]

I have a 2009 115 4s Merc and use 87 octane right out of the pump. I run the Merc injector cleaner about every 5th tankful. When I picked up my boat at Rapid Sports the I asked the mechanic (Mercury Certified) the same question. He said my engine was engineered to run on 87 octane and anything higher does nothing to improve performance and might even cause damage over the long term because it will fire hotter. He said do the required maintenance and the motor will run trouble free for years.

[Fishaholic2011]

Oxy free gas is the way to go for me, don't have to worry about prolonged storage. I never add anything to my gas all year. The part that bites is the price! To me its worth being hassle free.

[boatfixer]

Thanks I was wondering what others used. The manual states 87% octane and I think it could have 5 or 10 % ethanol will have to double check. I asked because I had a 50hp 4stroke Honda before and the dealer said it run better on premium.

If the manufacture states 87, then there is no need to run premium. Premiums actuall contain fewer hydrocarbons and contain other additives to boost octane. This slows the burn down and can even leave deposits behind and thats what can cause problems (not that it does in all cases). Its a myth that it burns hotter and gives you better performance.

[snowfighter]

Thanks for the input will go with the manual recommendations.

[Juan Grande]

Yep, I have a Merc 115 4 stroke (2005) and I run regular gas and run Stabil through it every fall. I guess I should use injector cleaner more frequently, but it has run great since I got it and starts on one turn every time.

[Superduty]

In a perfect world, 87 octane ethanol free gas would be the fuel to burn. It's very hard to find in MN. You are better off running 87 octane with ethanol than running a premium with a higher octane rating. Like others have posted, the premium burns longer and can damage your engine. Follow the owners manual with 87 octane and add the proper Mercury quickleen additives to compensate for ethanol and engine deposits. Your warranty can be void if you don't follow the fuel recommendations.

[kfk]

I have a 2011 115 4 Stroke and use "regular" gas at every fill although I do use Mercury fuel additive at every filling. I winterized it with Stabil in the tank and then running it until it was through the motor. It took off immediately this spring. It's always ran perfectly without any hiccups. No need for premium in my book and I've never used premium in any of my outboards for the 30 some years that I've owned boats. I realize that some folks claim the quality of fuel isn't as good as it used to be and ethanol hasn't been around the whole time, but I've never experienced any problems using regular in my outboards and I've burned a considerable amount of gas in those 30+years.