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  1. #1

    Default 1978 Mercury 402 Water pump question

    Hello
    I have a 78' 402.
    I have removed all the bolts for the lower unit, and it has seperated about 1/2". I believe the drive shaft is seized in the crank. But want to check and see.
    Should this be in forward, nuetral or reverse for removal?
    What am I forgetting?
    Thank you for any help.
    -Kevin

  2. #2
    Fleet Admiral WillyBWright's Avatar
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    Default Re: 1978 Mercury 402 Water pump question

    Shift position will have no bearing on separation. The important thing is to have the gearcase in the same shift position as the shift lever when reassembling. I assume you got the nut or bolt up inside the trim tab cavity. If you hadn't, you wouldn't have anywhere near that 1/2 inch.
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  3. #3
    Petty Officer 2nd Class tredragon's Avatar
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    Default Re: 1978 Mercury 402 Water pump question

    I know this post is old... but today I just pulled the lower unit from a Mercury 500 (circa 1969... Thunderbolt)...

    What I found was this (hopefully this helps others):

    Pull the 5/8 nuts ALMOST all the way from either side of the lower unit. Pull the 5/8 from underneath the lower unit (above the prop). Get a 3/8 allen wrench to pull the allen bolt from the small hole in the extreme rear of the lower unit. This will release the "fin" from directly above and behind the prop. Once the "fin" is removed... there is a 9/16 nut to remove. Even after that... we had to put it to full forward gear to get the splines to release... and move the prop until it just straight dropped down.

  4. #4

    Default Re: 1978 Mercury 402 Water pump question

    I'm looking for "Maintenance Manual" of Mercury 402 (4O hp, 2 stokes), in french if possible, or in english.
    Where can I that find?
    Thanks for your help.
    thierrynetten@hotmail.com

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