9.9 mercury 4 stroke- is premium gas ok?

[rooooney]

Is it ok to run premium gas (93) through a small outboard, or should I stick to 87?

 

[RLT III]

Re: 9.9 mercury 4 stroke- is premium gas ok?

I have a 50hp and I run 89 because I've heard after the ethanol mix it's really only 85 and really they should be run with 87 so that's why i do 89 in the idea of losing 2 octane with the ethanol I'm back at 87

 

[gss036]

Re: 9.9 mercury 4 stroke- is premium gas ok?

I guess the good thing about the 9.9 HP is that you are not throwing away a lot of money. The engine is made to run on regular gas and will probably run better on it than on Premium. Definitely won't hurt it though.

 

[milehighboater]

Re: 9.9 mercury 4 stroke- is premium gas ok?

The only gas I am wary over is the 91 octane Shell premium gas. It has nitrogen in it to remove engine gunk, and I don't know how it effects my 2-stroke so I am sticking to the midgrade 89 it seems to run well and my plugs look good.

 

[Silvertip]

Re: 9.9 mercury 4 stroke- is premium gas ok?

87 octane is 87 octane. If the engine is designed to run on it, there is no advantage to running more expensive fuel. In fact the additives in higher octane fuel can be worse for the engine.

 

[rooooney]

Re: 9.9 mercury 4 stroke- is premium gas ok?

Im not running it for any advantages - i just get nice fuel perks at my grocery store. I usually get a huge discount on up to 30 gallons and my car only takes 21 so I put the rest in the boat. My car requires premium so as long as it doesn't hurt the motor i'm happy- thanks

 

[mjc3834merc]

Re: 9.9 mercury 4 stroke- is premium gas ok?

Somewhere I read that Nissan recommended 91 octane in my Nissan(Mercury) 6hp 4 stroke. Can't remember where. Anyway, here's a page from my manual. Says "Unleaded, MINIMUM pump posted 87 octane gasoline recommended. Caps are mine. Also goes on to talk about the nasty things that can happen with ethonol. If they deceide that any damage to your motor was caused by ethanol it isn't covered by warranty. Here in Minnesota I can only get 91 octane ethanol free gas. Thats all I've run in it. Starts and runs just fine.

Thats what I run in my 21 year old 35hp Mercury 2 stroke too. permixed with oil ofcourse. Hasn't hurt her.
Mike

 

[JB]

Re: 9.9 mercury 4 stroke- is premium gas ok?

Somewhere I read that Nissan recommended 91 octane in my Nissan(Mercury) 6hp 4 stroke. Can't remember where. Anyway, here's a page from my manual. Says "Unleaded, MINIMUM pump posted 87 octane gasoline recommended. Caps are mine. Also goes on to talk about the nasty things that can happen with ethonol. If they deceide that any damage to your motor was caused by ethanol it isn't covered by warranty. Here in Minnesota I can only get 91 octane ethanol free gas. Thats all I've run in it. Starts and runs just fine.

Thats what I run in my 21 year old 35hp Mercury 2 stroke too. permixed with oil ofcourse. Hasn't hurt her.
Mike

That sticker says to use 87 octane gas. The 91 it refers to is by RON number, which is the same thing as 87.

It also says that E-10 gas is okay, which means that the warranty covers E-10.

You seem to be interpreting it as you wish it was, rather than by what it actually says.

 

[mjc3834merc]

Re: 9.9 mercury 4 stroke- is premium gas ok?

No the sticker doesn't say to use 87 octane it says not to use anything less than 87 octane. That would be my interpertation of "minimum". The only 91 octane I refered to was the 91 octane non-oxygenated gas I use here in Mn.

I guess you can interpret "Damages resulting from the use of gasolines that contain alcohol are not covered under the limited warranty." any way you want. As long as I can get gas that DOESN'T contain alcohol I'll use it. Thats what these forums are for. Asking for and getting other peoples opinoins.
Thats my opinion.
Mike

 

[trendsetter240]

Re: 9.9 mercury 4 stroke- is premium gas ok?

I run 94 or 91 octane gas in my outboards only because it is the only available without ethanol.

I also occasionally run 89 from the fuel dock which is 5% ethanol and I don't worry about it.

 

[verado7]

Re: 9.9 mercury 4 stroke- is premium gas ok?

when the motor is young run 87 - if you keep it for 10 years bump up to 89 - as engines wear - they will aquire some detonation(knocking) like any engine - due to blowby - haveing a higher octane will minimize it - 89 wont hurt anything - if at all you might have a slightly higher consumption but on a 9.9 thats pretty slim - you will get the benefits of added cleaners - 91 only benefits older motors ( 80's) / early ( 90's) and older .