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Thread: 1971 Mercury 75

  1. #1
    Join Date
    Sep 2017
    Location
    So. Colorado
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    7

    Default 1971 Mercury 75

    Hello, to all, from Southern Colorado!!! I am hoping to find some help in locating replacement coils for a recently acquired 1971 7.5hp Mercury motor. I purchased a 12 ft. aluminum boat (decent shape), trailer (not much), and this 7.5 for $250. I knew I was taking a chance on this motor, but figured for $250 I could invest a little money, if necessary, and still be ok. I have ordered insulation blocks, which will be here tomorrow, and soldered new wires on to the screws that attach to the points, the existing were rotted. I have attempted to test the coils, and get no resistance through any of the windings !!! Wondering if I am testing them correctly. Anyone have a source for the proper testing procedure? Assuming the coils are bad, is there a current source for replacement coils for this motor? I have been unsuccessful on the internet. I would like to get this old girl running, and am having a bit of fun in troubleshooting her problems, just don't wanna spend more than the cost of a new motor to get it done. Thanks for your help.

    Gary

  2. #2
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    15,190

    Default Re: 1971 Mercury 75

    Replacement coils are available on E-Bay and Amazon. About 30 bucks each. You should see SOME resistance on a good coil.

    Jeff

  3. #3
    Join Date
    Sep 2017
    Location
    So. Colorado
    Posts
    7

    Default Re: 1971 Mercury 75

    fastjeff, thank you for the reply. Aren't the coils I am seeing online for electronic ignitions?? Mine is a point system.

    Gary

  4. #4
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
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    15,190

    Default Re: 1971 Mercury 75

    Points? It has a distributor, right, but also a switch box (located in front of the carbs).

    I'm confused. Merc made a 65, 70 and 80 and 85 hp back then. How many cylinders is your motor?

    Jeff

  5. #5
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    13,649

    Default Re: 1971 Mercury 75

    ???----He has a 7.5 hp !

  6. #6
    Join Date
    Sep 2017
    Location
    So. Colorado
    Posts
    7

    Default Re: 1971 Mercury 75

    Jeff, racerone is correct. Motor is a 2 cyl., 7.5 hp with 2 sets of contact points.

    Gary

  7. #7
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
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    Default Re: 1971 Mercury 75

    Ooooohhh! Seven POINT five. Different animal.

    Jeff

    PS: Curse Carl Kiekhaefer for adapting that dopey hp times ten nomenclature! I wonder how many 'Merc 200s' were confused with 20 hp vs 200 hp (and visa versa). HNow about you? Ever get them mixed up, eh?

  8. #8
    Join Date
    Sep 2017
    Location
    So. Colorado
    Posts
    7

    Default Re: 1971 Mercury 75

    fastjeff, I, too, find the model numbers confusing or, at least, misleading!!! An update on the 7.5 Merc. Received the insulation blocks, from CDI, and got them installed with little trouble. Set the points at .020", a bit of a pain!!! I soldered ignition wire to each of the ground wires on the coils and attached them to a solid ground on the motor. I did not feel the method of running them on the outside of the rubber coil insulators and hoping they would properly ground to the housing was very efficient. Got the rest of the motor reassembled, and now have a very robust spark from both coils. I will, hopefully, be trying to start this motor today. I will report back on my progress

  9. #9
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
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    Default Re: 1971 Mercury 75

    Good work!

    I hope you removed the kill switch from the circuit, for operating it is what destroys PM ignition systems. You can, instead, idle her down and pull the choke to shut it off.

    Jeff

    PS: The singles with PM ignition don't have a kill switch and they are far more reliable.

  10. #10
    Join Date
    Sep 2017
    Location
    So. Colorado
    Posts
    7

    Default Re: 1971 Mercury 75

    Good evening, folks. I am writing a final update on my new, to me, 1971 7.5hp Model 75 Mercury motor. After re-working the ignition wires, and getting strong spark to both cylinders, I found I was not getting fuel. Ordered rebuild kits for the carb and fuel pump, from Marine Engine, and rebuilt both. After cleaning and installation, I primed the fuel system and had to pull the starter rope a total of four times before the motor sprung to life!!!! She now purrs like a kitten. Thanks to all on this forum who helped me figure this out. Sure glad we can still get parts for these old ladies. I am proud to have her on my 14 ft. boat. Thanks to Old Mercs, and Marine Engine for having repair parts available, also. Just picked up a '79 9.9hp Evinrude for my next project!!!

  11. #11
    Join Date
    Sep 2003
    Location
    New Tripoli, PA, USA!
    Posts
    15,190

    Default Re: 1971 Mercury 75

    Glad to hear it. Those are great running little motors that never got the respect they deserve (thanks to the emphasis on Merc's larger motors).

    Jeff

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