Alternator voltage

[canuckboater]

Does anybody know what the voltage is supposed to be on the yellow wire? I'm getting 11 volts with key on engine not running. Yellow wire goes to voltage regulator then to resistance wire to coil.
Thank you

 

[alldodge]

With the yellow going to the coil, its should be sense lead or what can be called the excite lead. This lead should turn the ALT on when ignition turns ON. The wire has been replaced because I'm not finding where OMC used that color at that location

Your ALT is the lower left

https://bpi.ebasicpower.com/charge/alternatorwiring.htm

 

[canuckboater]

Thanks for the response
Here is what I believe to be the wiring diagram for my set up....
11 volts seemed a bit low to me on that terminal given that it was wired into a voltage regulator I was expecting the voltage to be higher

 

[alldodge]

Coming from the regulator I would expect to see a bit lower voltage due to internal circuity. Once started it should be closer to battery voltage. The regulator adjust the energizing voltage based on what it sees coming in on the Purple wire

 

[canuckboater]

I'll check it once I get the boat in the water and running

 

[canuckboater]

So I've had the boat (OMC 120) in the water and hooked up a remote voltage meter to the coil so I could monitor while trouble shooting. My basic problem I'm trying to overcome is that once warm the boat will stall at idle and won't re-start until it cools down unless I use a jumper wire from battery to coil. Most of the season the boat would fire up just fine when first splashed. Last two times I had to use the jumper wire from the battery to get her to fire. It appears that the 12 volt feed from the starter is not doing what it is supposed to. When I turn the key on I have 11 volts at coil, when cranking it drops to next to nothing so I expect the starter needs attention ( spins the motor no problem ...just no fire). Once running the coil receives a touch over 12 volts and stays consistent (a bit higher than what I was expecting). The coil does not get overly warm as I can still place my hand on it. When I idle down the voltage drops and the engine stalls out when the voltage hits around 10.5 volts, placing me in a precarious position at times. Had the engine cover off while running and noticed the lower mounting bolt of the alternator had backed itself out about an inch and half. The nut had come off and the alternator was shaking more than it should have. Managed to get that problem fixed and it seemed to hold its idle better than before but it still died on me. I think the starter is my issue for not re-starting and getting the voltage to the coil and am planning on pulling it and getting it rebuilt/checked over but I'm not sure why I'm stalling. Perhaps the shaking of the alternator has worn out it's bushings and it to needs a re-build/ replacement. The voltage seems to be there but is it possible it is not producing the amps it needs?. Any thoughts or suggestions on how I can keep this engine running at low speed?. I have replaced the points, condensor and the coil is new, wires, boots and plugs all appear to be in good shape. This is my second season with this boat and this problem started at the very end of last season. I've spent this season chasing this gremlin and have already been through the fuel system. Thanks in advance

 

[Scott Danforth]

your alternator voltage should never drop below 13 volts, it should always be higher than battery voltage to charge the battery.

you want your coil running about 10 volts so you dont burn the points. that is over 13 volts prior to the ballast resistor.

when you set your points what is the dwell. you should be at 32 degrees for your motor. then you should set your timing at 4 degrees BTDC

 

[canuckboater]

Thanks for your response.
The volt meter on the boat reads 13 volts so I believe the alternator is doing its job on maintaining the battery. I am not sure what the voltage output is supposed to be on the small yellow wire that feeds the voltage regulator. Currently I measure it 11 volts with the key on. From the voltage meter it feeds the resistance wire to the coil so I'm not sure why I am getting 12+volts at the coil while running with some throttle. I haven't configured a method to voltage test what the alternator is pouring into the regulator yet while it is in operation. I may have to do a bit of homework on the dwell. I did not adjust the timing at all as the boat idled and ran fine when I first acquired it but that may need to be checked.
I was expecting to see 10 volts at the coil while running and was surprised to see it a tad bit over 12 thinking that surely between the regulator and resistance wire it would get knocked down to 10 v. Currently she stalls out before she hits 10v as she idles down. Would the dwell and timing have any affect on the voltage feed to the coil?

 

[alldodge]

Power feeding the coil comes from the battery to the 10 pin connector, to the key, back to the 10 pin connector, to the coil

I would suspect the 10 pin connector and internal connections

 

[canuckboater]

Hmmm power feeding from the battery you say....Am I not reading this wiring diagram properly? I was following the resistance wire hooked to the voltage regulator. I'll check the 10 pin connector

 

[alldodge]

Your correct it is a resistance wire but power does go to/from through the 10 pin

Your voltage going that low means there is a bad connections.

 

[alldodge]

 

[canuckboater]

Ahhh ok...Thanks for pointing that out