Octane 87or 89???

[Nitro 882]

To help get through the winter I have read all my fishing mags, cover to cover, for the umpteenth time.

I just came across an article again that makes the claim that 89 octane fuel "has less additives and burns cooler" than 87 octane fuel.

What do you guys say?

(By the way, the article is in Bass Times, May 2009 on page 10)

[Wayne P.]

I say use the grade of fuel recommended by the mfg of your engine.

[Hot Rod]

Yeah I remember that article.  My manual says I should only run 87 in my '04 150 Johnson.

But my certified mech told me I should never run less than 89.

I asked what gives.  He said :"the reason the manual says that is that most people don't want to spend more on fuel than they have to spend.  Therefore, the manufacture recommends 87 in the manual so it looks like it is less costly to operate".

I don't know.  Mine seems to run much better on 89 or higher but most times when I'm topping off I'm adding it to a half a tank of "stale" fuel so its probably lost some octane and balances out somewhat.

[Way2slow]

The engines compression ratio and state of tune is what determines which octane gas it should run. A properly tuned engine, designed to run 87 octane gains no benifits from running higher octane. It's just the opposite. The higher octane burns slower so you actually don't get a full burn, which leads to a slight loss in performance and increase carbon deposits on the piston domes.

Now, if you're one that uses his boat only every now and then, and it sits for several weeks or months, with the same gas, it would probably pay you to buy the next grade up. Gasoline looses octane very quickly. I will not run gas in my boat motors that's over a month old. Since I no longer fish two/three times a month, when I come in from fishing, I have an electric pump that I pump all the gas out of my boat and put it in my vehicles. I do not leave it sitting in my tanks.

[shimanogloomis man]

I have a 06 stratos with a 225 etec and when i bought it they told me run 89  ;D

[burleytog]

Owners manual for my Merc says 89.

[RoLo]

I'm sure it depends on the make, model, year & engine type.

I'm running a 60-hp, 4-stroke, 2010 Mercury,

and the manual recommends "87 Octane" with 10% Ethanol tolerance (that's what I run).

Roger

[simplejoe]

I have a 97 Johnson 200 and manual says to run 87. Since I have a 2 stroke I also run Johnson Carbon Guard and Sta-bil Marine.

[South FLA]

The engines compression ratio and state of tune is what determines which octane gas it should run. A properly tuned engine, designed to run 87 octane gains no benifits from running higher octane. It's just the opposite. The higher octane burns slower so you actually don't get a full burn, which leads to a slight loss in performance and increase carbon deposits on the piston domes.

Now, if you're one that uses his boat only every now and then, and it sits for several weeks or months, with the same gas, it would probably pay you to buy the next grade up. Gasoline looses octane very quickly. I will not run gas in my boat motors that's over a month old. Since I no longer fish two/three times a month, when I come in from fishing, I have an electric pump that I pump all the gas out of my boat and put it in my vehicles. I do not leave it sitting in my tanks.

^^^^^^^^^^^^^^^^^^^^^^^^

This is what my Yamaha tech said also.

By the way what make and model electric pump do you have to pump out gas from tanks? I figure if I do this it will save me having to by Stabil a times and have fresh gas on every trip!!

[Way2slow]

The pump I use is a pump I use with my hotrod motors when I put one of them on  http://www.jegs.com/i/Carter/180/P4594/10002/-1?parentProductId=748050.  It's more pump, and probably more expensive than what you need, but it's already mounted in the boat so I only have to switch a hose and turn it on.  My ficht motor does not use it.

I also use a one gallon plastic gas container and mix approx two ounces of SeaFoam to a 1/2 gallon gas and connect a hose from the primer bulb to it.  Every four - six weeks I run the motor on the hose long enough to pull a quart or so of fresh gas into the motor.  Do this and you will never have carb and fuel related problems caused by old gas.    I keep a spare set of spark plugs in the boat, if you run it several times, sometimes it carbon fouls the plugs so I just swap them out and sandblast the fouled set.

[5bass]

I've got a Mercury 250 Pro XB. It won't run right on anything less than 93.

[DINK WHISPERER]

I run 89 in my 96 Merc 150 HP EFI