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jump start motor

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  • jump start motor

    hello, i have a mid 70's 70hp 3 cylinder merc that's ready to be started but i don't have controls . how can i jump start the motor . i just want to start it to see how it runs it's on a stand and not going anywhere. thanks for any help

  • #2
    Re: jump start motor

    Unless the foot is in enough water to cool it or you have "muffs" feeding water to it don't even think about starting it, Turtles.


    • #3
      Re: jump start motor

      thanks JB .I i installed a new impeller and a new stator (had no spark)everything's ready to go wouldn't think about starting it without lower unit in water just not sure how to jump start (no controls) without messing something up


      • #4
        Re: jump start motor

        Inside my cowling (Merc 115 inline 6) is a rope with a handle on it that can be attached to indents on the flywheel for pull-starting. See if yours has the same. Also, I once saw an older guy start an outboard by attaching a drill with a socket attached somehow to the top of his flywheel....boy does that sound crazy but darn if it didn't work!
        24' Aqua Patio 115 Johnson 1990, 8hp 1986 Mariner Kicker
        Gunpowder River, Upper Chesapeake


        • #5
          Re: jump start motor

          I think he is more looking for where to connect a wire to disable the ignition portion of the controls.

          Personally I have no idea how to "hot wire" the motor without the controls but I think that is what he is looking for.

          Good luck and I wouldn't mind knowing just in case something happens someday and I need to bypass the key.


          • #6
            Re: jump start motor

            the motor started on the first pull with a pull cord off the flywheel . kind of easy when i was working on the motor (new stator ). i didn't think i would be able to pull start it without pulling it right over being it's on a stand. also read that a universal starter switch is no good on an outboard too many volts or something


            • #7
              Re: jump start motor

              Careful, on some motors you can damage electric and/or ignition components if you run them without a battery.
              1980 Sylvan Aluminum 18' Sportster I/O - Mercruiser 140, Honda 7.5 Kicker, Bennett M120 Tabs
              1974 Glastron V-179, Mercruiser 140
              1984 16.5ft. Alumarine Sealark side console with 82 Merc 50
              Manitoba, Canada


              • #8
                Re: jump start motor

                You will want a battery attached. What you will need to do this safely is:

                From battery positive post:
                1) Nice fat cable (min 4AWG, or red side of jumper cable would work) to big positive post on the starter solenoid that the red harness cable goes to; this is going to provide your starter power when you activate the solenoid.
                2) To the + post on rectifier (min 16AWG, 14AWG better); if you don't do this, you could fry the rectifier.
                (Note: if the internal harness is all hooked up, you won't need wire 2) above, because the rectifier will already be tied to the battery through the harness at the positive post of the starter solenoid)

                From battery negative post:
                3) Nice fat cable (min 4AWG, or black side of jumper cable) grounded off nicely to the powerhead metal.
                4) To the black wire (ground) post on starter solenoid (min 16AWG, 14AWG better).
                (Note: if the internal harness is all hooked up, you won't need wire 4) above, because the solenoid will already be grounded through that harness)

                Now between the positive battery post and the starter solenoid yellow wire (start) post, you want to install:
                5) a remote momentary push-button starter switch (maybe auto parts store). Starter solenoid only pulls maybe 5 amps, if you need to spec a switch.

                If you want to remotely activate the choke, you'll also need to wire:
                6) a momentary switch between the battery positive and the choke solenoid post (grey wire), also should pull no more than 5 amps. But the motor should have a manual choke pull near the solenoid, so this is totally optional.

                If you want to be able to kill the motor quickly without simply letting the carbs run out of gas (i.e., you want an emergency stop), then you will need to wire in:
                7) a button (either momentary or on-off OK) or better yet a dead-man between one of the orange kill terminals (either at the switchbox or at the top of the mercury switch) and the powerhead (ground). Be very careful, there's not a lot of amps (maybe 5-10amps) there, but a HELL of a lot of volts (upward of 250-300VDC). Or optionally, just pull the choke and starve it for air (though that could take a few seconds to shut off...depends on your definition of "emergency" timeframe I guess).

                Don't worry about the brown wire, you won't need tach for this; although you could easily hook one up if you wanted.

                MAKE SURE all your leads and jumper cables are SECURE. If any connections come loose while the motor's running, you can fry ignition parts.

                Oh, and MAKE SURE it's in neutral when you start it up; without a control box, the neutral start switch isn't in place. The prop will spin freely by hand in either direction when you are in neutral.

                San Diego, CA "The 619"

                2000 Sea Hunt Triton 172 CC, 2014 Mercury OptiMax 125

                "It's always easier to ask forgiveness than permission" -Colin Powell, et.al.


                • #9
                  Re: jump start motor

                  Originally posted by turtles11756 View Post
                  hello, i have a mid 70's 70hp 3 cylinder merc that's ready to be started but i don't have controls . how can i jump start the motor . i just want to start it to see how it runs it's on a stand and not going anywhere. thanks for any help
                  Good to hear you figured it out. Pretty simple huh.. So, how did you stop it.. I suspect you figured out how to make a kill switch or just cut the fuel.


                  • #10
                    Sign up today
                    Re: jump start motor

                    thanks guys, and i read somewhere the battery must be hooked up. better read up on that again . i let it run for about an hour so maybe i got lucky with electrical / ignition .it idled well but seemed to buck a bit when i gave it some gas maybe out of time a little or the carbs need cleaning. was dead as a door nail (rotted wires) when i brought it home last august but the compression was in the 140's on all 3. thanks again i will try that switch hook up aj