50 HP Johnson problem

[Bruce Buck]

Okay all you mechanics. I have a '71 50 HP Johnson ES That starts right up with the key but then won't shut off when I turn off the key. I un hooked the battery but still running. Finally had to unhook the white wire from the sending unit at the power pack. Any ideas?? I'm still new at this outboard motor stuff so please be patient with me. lol
thanks in advance, Buck

[Helmar]

Boy, good question....I would like to know more about why myself.

Not sure how many OMC guys we have here ???

[Tim_Mattson]

Bruce,
You normally don`t ever want to onhook a battery on a running outboard as the charging system will try to charge Infinity.:donttouch:
Power packs do fail on the kill circut but a "keyswitch elimination test" is usually first done.Pull spark plugs ,unplug wire harness and see if it sparks with flywheel turned.....if so,then most likely the switch or harness.
Borrowing a working control with same color on plug will be easist,guesing you have an older black or yellow one?
The "M" positions on keyswitch will be where the circut is either cut or connected.......at least on the red plugged omcs I work on and own.
Choke to kill it next time too or pull plugs and listen for spark as you track down the issue.
TimM

[Super Sportster]

Is a '71 50hp a twin cylinder? My '74 40hp was still equip with points and to kill it was a wire from each set of points completing a circuit to each other through the ignition switch.

[Tim_Mattson]

Ah, now I see the light....it could use a simple on/off push button to ground the Magneto wire as needed."Push to stop" is commonly seen on older OMC key or switch/choke panels.....might be a simple add and be done.Ahorn button would do the job nicely if current keyswitch can`t do it.
TM

[Lootas1]

That post (and a sunny, warm, calm day) made me think of firing up our 'Rude 50. Hadn't recharged the batteries since sometime in 2011. Fired right up and ran smoothly on fuel from each tank (used marine Stabil on them when I retired the boat in October). Thought of washing and waxing Rosario but even under the boat cover, it was covered with that yellow pollen from the alder trees. Decided I'll wait until the day before taking her out on the saltchuck to clean her up. Turned the switch. Motor stopped. What more could anyone ask for? Come on SPRING, SUMMER, FALL!

[Super Sportster]

Ah, now I see the light....it could use a simple on/off push button to ground the Magneto wire as needed."Push to stop" is commonly seen on older OMC key or switch/choke panels.....might be a simple add and be done.Ahorn button would do the job nicely if current keyswitch can`t do it.
TM

Yep that will work. The difference between magneto and battery ignition switches, in the off position magneto is a closed circuit while the battery is an open circuit.