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  1. #1
    Member
    Join Date
    Feb 2010
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    Sherman
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    20

    7.5 hp Mercury been sitting for years

    My dad bought an older 7.5 hp Mercury sn3104477. I think it's a 70 something model. It's in great condition but it hasn't been used in several years. What recommended maintenance should I perform before attempting to start it. Thanks in advance.

  2. Member
    Join Date
    Mar 2017
    Location
    Westport, Washington
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    1,508
    #2
    Pull the float bowl and make sure it is clean, check the points to see if they are clean and set. Change the lower oil and plugs. Fire it up!

  3. Member
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    Feb 2010
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    Sherman
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    #3
    Thanks TP16. Should I worry about the water pump?

  4. Member
    Join Date
    Mar 2017
    Location
    Westport, Washington
    Posts
    1,508
    #4
    You can always try it but replacing one that is that old is the best idea. It may have been changed already but for the cost, and once you are in there anyway if you check it, it would be worth it to go ahead and change it for piece of mind if nothing else.
    The problem may come from corroded fastiners that snap off or have no threads left. I have had some that came right apart and were fine and others that turned into broken off bolt nightmares.
    From what I find is that is a 1971 outboard.
    This guy has some good info on old outboards.
    http://www.leeroysramblings.com/Outb...20related.html
    Last edited by TrackerPro16; 12-05-2018 at 02:00 AM.

  5. Member
    Join Date
    Nov 2015
    Location
    central IL
    Posts
    78
    #5
    There are two impellers for that engine. Take it apart if it is a mercury part
    there will be a part number on it.

  6. Member
    Join Date
    Oct 2016
    Location
    Santa Cruz, California
    Posts
    317
    #6
    Per the serial number the impeller part number is 89981.
    David Patten
    Automotive and marine technician.

  7. Member
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    Feb 2010
    Location
    Sherman
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    20
    #7
    So I'm just now getting time to start on this project. The main issue I have so far is the wiring coming from the points are corroded and falling apart. I'm trying to determine if I have to replace the assembly or if the wires can be replaced. I tried looking up the serial number on European Marine's website but did not get a match. Anyone have experience repairing the wiring?

  8. Member
    Join Date
    Jun 2013
    Location
    LONGVIEW TEXAS
    Posts
    13,941
    #8
    seen it done/ soldering iron
    .................................................. ...the scariest thing in life is the unknown ...................................

  9. Member
    Join Date
    Feb 2010
    Location
    Sherman
    Posts
    20
    #9
    Repaired my wires from the trigger and verified spark from one coil but not the other. Moved the point wire from the non working coil to the good one and got spark so I think I'm good to the coils. Anyone have other suggestions to verify the one coil is bad?

  10. Member
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    Feb 2010
    Location
    Sherman
    Posts
    20
    #10
    So I'm still working through issues on this motor. I've replaced a bad coil and cleaned the carb. Now it at least acts like it wants to start on occasion. One issue that I have now is the starter will pull fine several times in a row and then it locks up and I about pull my arm out of the socket. I verified motor was not in gear and when I rotate the flywheel it moves fine. It will pull smooth a few more times and then do it again. Is this a timing problem?

  11. Member
    Join Date
    Jun 2013
    Location
    LONGVIEW TEXAS
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    13,941
    #11
    very possible
    .................................................. ...the scariest thing in life is the unknown ...................................