Mercruiser 120 continue running when switched off

[airman1094]

Was trying to get my ole boat ready for the water...it starts and runs fine. Had to replace the alternator today. Tried out the alternator and it generates power...but when switched off the engine kept running and the voltmeter was bouncing. Had to choke off the air to the engine to shut it off. I've never experienced this before. Wired it just like the old one which worked fine before. Alternator has 3 wires...one positive, a ground, and a small wire that goes to one of the little blade connections at the top of the alternator. I had put the wire on the wrong blade at first and generated no voltage but putting it on the right one (i think) it now generates voltage but it wouldn't shut off....did I burn a diode or something by mismatching the little blade wire? Sorry I don't know the proper terminology.

 

[alldodge]

Might have a ignition switch problem or there is another wiring mistake. Have a look at the wiring an d note the White wire supplies power to regulator and coil

 

[airman1094]

That's helpful. Im thinking it may be the ignition switch...I have to turn it on and off a few times to get the starter to go...if that don't fix it I think I'll check those wires to make sure they are kosher

 

[alldodge]

.I have to turn it on and off a few times to get the starter to go..

That is probably the issue

 

[matt167]

alternator can be back feeding the ignition circuit.sometimes there's a diode to prevent it

 

[Bt Doctur]

sounds like the wrong alt is being used , maybe an auto version