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  1. #1

    With winter approaching, here again is Mercury's official 240EFI winterization...

    This is straight from Mercury via a personal phone call to their engine technicians. Updated to include Mercury part numbers for the filters, NGK part and stock numbers for the plugs, and approximate prices.

    Official Mercury Winterization Process for 240EFI Engine

    In a small outboard fuel tank, mix fresh non-alcohol/ethanol gasoline with the recommended amount of fuel stabilizer and Mercury Quickleen. Add twice the normal amount of Mercury Premium Plus 2-stroke oil. (RLH note: Mercury calls this “witch’s brew”.)

    Disconnect the main fuel tank hose from the engine’s inline fuel filter and connect the outboard fuel tank hose in its place. Connect water line to flush port and turn on water. Start and idle engine.

    Run until smell of exhaust changes, indicating that “witch’s brew” has made it through the entire engine. Stop engine. Disconnect temp fuel tank and drain any remaining contents into main fuel tank.

    Place a catch container below vapor separator drain plug, remove drain plug, drain vapor separator, and reinstall plug. Direct quote from factory tech: “You do not want fuel pooled in the vapor separator all winter long.” (RLH note: This is the first reference I’ve seen anywhere relating to winterizing the vapor separator.)

    Restart engine with no fuel tank connected and wait until engine stalls. Remove key from ignition and disconnect battery. Do NOT turn key to “ON” or “START” positions again, as this will enable fuel pump.

    Shut off water, disconnect from flush port, and wait for water to finish draining.

    Reconnect main fuel tank hose.

    Drain main fuel tank and leave empty. Use fuel stabilizer (Sta-Bil or Mercury Fuel Additive) if tank cannot be drained.

    My own additions:

    Replace fuel/water separating filter with new, empty filter. Mercury part number 35-18458Q4, ~$22.

    Replace inline fuel filter with new, empty filter. Mercury part number 35-889615, ~$8.50.

    In Spring, replace spark plugs after first full tank of fuel has been consumed. NGK part number BPZ8HS-10, stock number 3133, ~$6 each, do not substitute.

    Note that these instructions do not include changing the front and rear jetdrive lube, which is a vital part of winterization that should be performed at the same time.

  2. #2
    seadoodude's Avatar
    Join Date
    May 2008
    Cypress, TX
    thanks for the info. I ran the witches brew thru the engine today. However I did not find the drain on the vapor seperator. I'll have to look again, but we don't have much of a winter down here so I'll probably just run it once a month or so to keep it going during the off season.

    Btw, I found the drain screw in the shop manual. But have concerns about leaving fuel systems dry. What is better, leaving treated fuel in or draining and running dry? Depends who you ask.

  3. #3
    The vapor separator drain screw is a small flat brass screw at the bottom. It's easily accessible and uses a flat blade screwdriver. When winterizing this year and after letting the engine run until fuel exhaustion, I found very little fuel remaining in the VS.

    Regarding "wet" versus "dry" storage - I've heard both arguments. The best choice may depend on the equipment in question, what the fuel remains in contact with during the winter, etc. I've decided to do what each manufacturer recommends. For my 240EFI, that means storing it "dry". For my Rotax 787 engines, that means "wet".

  4. #4
    Join Date
    Oct 2006
    if you guys want the factory manual let me know

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