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  1. #1

    Default OIL in fuel tank?

    This is my first outboard and have a simple question for you folk. It's a 40hp Merc Mariner that has its own oil reservoir for the fuel mixture. I opened the cap on the gas tank and noticed there were oil mixed in the tank as well. Is this normal? Can the oil back feed itself to the tank? I just purchased this boat and just noticed it.

    <Bitin Bassard>

  2. #2
    Join Date
    Aug 2015
    Poulsbo, WA

    Default Re: OIL in fuel tank?

    Someone may have inadvertently mixed oil with the fuel in the tank. Or maybe there was a problem with the oil injection, no way to tell unless you ask the P.O. what the deal is with that.

    If you're sure about the oil in the fuel, you might try running the engine and see if it smokes a lot. That would be a good indication that you're getting plenty of oil from both the fuel tank and the oil injection system.

    If that's the case, it wouldn't be unsafe to run it on the water for some time, where you can see if the oil level in the tank changes. A drop in oil level is a purty good indication that the injection system is working.

    Does the alarm beep for a second or so when you 1st turn on the key? If so, the system should be working and alert you to any oiling failures or overheating.

    Be sure to check the fuel lines for deterioration, and double-check the oil lines too; any air sucked into the system will mess things up royally.

    HTH & let us know what you find..........ed

  3. #3
    Join Date
    Sep 2010

    Default Re: OIL in fuel tank?

    You have to verify the status of the oil injection system.----Failure to do so could be hard on your wallet.

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