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  1. #1
    Join Date
    Sep 2013
    Location
    cape cod
    Posts
    18

    Default Fuel For My New Mojo

    Hello all,

    I was reading my owners manual as I prepare for the 2014 summer. Our family just bought a 2012 Moomba Mojo and the manual for my new Mojo and it recommends 89 octane gas. I was talking to other people and they said you can mix and match 87 with 89 octane between fillups and to make sure you put marine stabilizer in the tank each time. I was wondering what people's experience/knowledge on this topic. Would 87 octane gas do considerable harm to the engine? Thank you in advance for any help

  2. #2
    Join Date
    Oct 2010
    Location
    Lake Wylie NC Area
    Posts
    770

    Default

    M,

    As far as the engine is concerned, you need to run the octane rating recommended by the manufacturer or higher, if the recommended octane is not readily available. It is not suggested to run a lower octane then whats recommended, due to the risk of pre-ignition, which if prolonged, can cause internal engine damage. Using a fuel stabilizer with each fill up has absolutely nothing to with the fuels octane rating. A stabilizer is only needed for storage or layup, to help slow the spoiling of the fuel. But, many of these products do offer some fuel system cleaning benefits, and can be used with each fill up. IMO, its a bit overkill. I would consult the manufacture about the specific additive you are looking to use.

  3. #3
    Join Date
    Aug 2010
    Location
    Acworth, GA
    Posts
    1,220

    Default

    Yup, use the manufacturer recommended or higher octane. What is the cost difference between 89 over 87, about a dime a gallon, so 4 bucks more on a 40 gallon fill up? Shouldn't be a budget breaker...
    Kraig - 2010 Outback V

  4. #4
    Join Date
    Jun 2008
    Location
    De Pere WI
    Posts
    4,161

    Default

    sure indmar is the same, but pcm lists octane rating, but also 10% ethanol blended fuel is approved so no need to use a stabilizer unless winterizing or not running for a month or so as mla suggests..
    '06 Supra Launch 20SSV-gone but never forgotten

  5. #5
    Join Date
    Oct 2010
    Location
    Lake Wylie NC Area
    Posts
    770

    Default

    To expand on sandm's post a little. Even an additive that is formulated to fight the side effects of ethanol, will not change/alter the percentage of ethanol in the fuel. Even with an additive, the ethanol is still corrosive on the fuel system components, and the higher ratios just increase the deterioration. The biggest benefit of an additive that targets ethanol, is to prevent/reduce phase separation when the ethanol blended fuel reaches its saturation point. Under normal conditions and normal use, I would not expect phase separation to occur. It should only occur when the boat is stored and the fuel is left to absorb moisture. if the fuel is being used and replenished with fresh, I dont expect a problem, but regular use of an additive should not cause harm.

    ive also read that testing has shown that in many station tanks, the ethanol can be well above the 10%. This is because its added to the fuel at the distribution center/tank-town, before going to the stations. Theres not regulating of the ethanol, and its great for watering down the actual gasoline, make it go further for the refiner. Gas is expensive enough, so it sux to not get what you pay for.

  6. #6
    Join Date
    Jun 2013
    Location
    Lake Orion, MI
    Posts
    429

    Default

    I can't imagine why anybody would ever intentionally not use the gas that is recommended by the manufacturer on a boat like this. My new neighbor recently started surfing with me, and he now brings a 5 gal gas can that he uses in his boat (2000 Malibu sunsetter I believe) to share the love. I didn't even think to ask him at first, but after we put it in I asked him if it was 89 octane. He said no it's 87. Off I went to get a 5 gal can of premium 91 to offset it lol! I also told him he might want to check his manual and see what they say for gas recommendation.

    For the pennies in difference per gallon, it's not worth it. Since we all own these types of boats, I know none of us need to fret over $4 per fill up difference.

    Speaking of ethanol in the gas...if you were to store the boat over the winter and the ethanol does absorb some moisture, wouldn't the water separator still catch that moisture once the boat is running?
    2006 Mobius LSV
    Previous ride - 2000 Supra Launch

  7. #7
    Join Date
    Sep 2013
    Location
    cape cod
    Posts
    18

    Default

    Thank you for your help

  8. #8
    Join Date
    Feb 2008
    Location
    Sylvan Lake, Alberta
    Posts
    473

    Default

    I put 400 hours on my 08 XLV and ONLY ran 87 and it never gave so much as a hic up.
    Levi
    Former owner of a 08 Mobuis XLV, Cat340, 2650 Lbs.
    I miss that boat!

  9. #9
    Join Date
    Nov 2010
    Location
    Katy, TX
    Posts
    4,150

    Default Fuel For My New Mojo

    Quote Originally Posted by 501 View Post
    I put 400 hours on my 08 XLV and ONLY ran 87 and it never gave so much as a hic up.
    As mike mentioned elevation plays a big factor as well. The higher up you are the thinner the air the less compression pressure the lower the octane needed. I know in Lubbock which is about 3400 ft above sea level you can't even buy 87, their low grade is 86 because the air is thinner. They say for every 1000 ft climb in elevation your engine loses 3% of its power. I don't think 87 to 89 is a big enough difference to cause any major damage. If it requires like 110 race gas and someone was using 87 then yeah, that would be a big deal. If you use 87 and don't want to pay for 89 then fill you tank half with 87 and half with 89 and now you have 88. Compromise haha


    Sent from my iPhone
    David

    2008 Mobius LSV, Gravity III , Wake Plate, Z5, Exile SX65c's, Exile XM9s, Exile XI12D, Exile Harpoon, Exile SM600.1 , Exile Xi800.4.

  10. #10
    Join Date
    Jun 2013
    Location
    Lake Orion, MI
    Posts
    429

    Default

    A lot of higher elevation areas (like CO) start at 85 octane for regular...I always wondered why that was and never realized that may be because of the elevation lol.
    2006 Mobius LSV
    Previous ride - 2000 Supra Launch

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