Mercruiser 140 (1984) - What started as key no longer turning off boat has evolved into boat not starting at all

[nola mike]

from ground to ignition coil + I have .03v, same as lug on solenoid

That's your issue. You should have 12v key on. Choke should have 12v also. See post #14. You didn't respond if gauges are also dead. There's a break in the circuit somewhere between the purple/red wire to the helm (do the accessories--blower, bow lights,etc work?) or in the purple wire from the ignition switch.

 

[Riflejake]

That's your issue. You should have 12v key on. Choke should have 12v also. See post #14. You didn't respond if gauges are also dead. There's a break in the circuit somewhere between the purple/red wire to the helm (do the accessories--blower, bow lights,etc work?) or in the purple wire from the ignition switch.

Gauges are alive. All accessories work.

Not sure how there’s a break in the circuit. The only wire, red and yellow, runs all the way back to the slave solenoid and continuity is fine. When switching to start position it has 12v.

Although, the choke not having 12v in the “run” position is due to the fact it rely on the coil to have 12v, so that makes sense.

Can I just run a wire somewhere where I have 12V on ignition and have that on the coil?

If so, will that mess up the purple gray wire leading to the starter?

 

[nola mike]

Gauges are alive. All accessories work.

So the fault is after the ignition switch.

Not sure how there’s a break in the circuit. The only wire, red and yellow, runs all the way back to the slave solenoid and continuity is fine. When switching to start position it has 12v.

It's a totally separate circuit after the ignition switch.

Although, the choke not having 12v in the “run” position is due to the fact it rely on the coil to have 12v, so that makes sense.

No. The choke supplies the coil.

Can I just run a wire somewhere where I have 12V on ignition and have that on the coil?

If you don't have switched power at the choke, you probably don't have it anywhere in the engine compartment. You still haven't tested that though.

If so, will that mess up the purple gray wire leading to the starter?

The purple/YELLOW is providing the coil with 12v when cranking.

 

[Riflejake]

So the fault is after the ignition switch.

It's a totally separate circuit after the ignition switch.


No. The choke supplies the coil.


Yes, although you'll make a mess for the next sucker (maybe you) that tries to figure out your kludge wiring job. And your choke won't work. Maybe. You still haven't tested it.


The purple/YELLOW is providing the coil with 12v when cranking.

The only wire going to/from the choke, other than ground, is that yellow/purple wire going to the coil. The last owner of this boat really goofed up a lot of things, such as the trim switch, speedometer, and a bunch of other electrical stuff. I’m already trying to figure out there’s F ups, don’t want to create more lol.

 

[Bondo]

The only wire going to/from the choke, other than ground, is that yellow/purple wire going to the coil. The last owner of this boat really goofed up a lot of things, such as the trim switch, speedometer, and a bunch of other electrical stuff. I’m already trying to figure out there’s F ups, don’t want to create more lol.

Ayuh,...... The key switch should have a B (battery) terminal, red wire, 12v, all the time,.....
A S (start) terminal, yellow/ red wire, 12v only in the start position,....
A I (ignition) terminal, purple wire, 12v in the run position,.....

The Start circuit yellow/ red wire feeds the slave solenoid, to the starter's solenoid tiny terminal nearest the block,....
The tiny terminal furthest from the block, feeds battery voltage to the coil's (+), Only when Starting,....

The I (ignition) circuit, usually purple wires, feeds the electric choke, 'n the coil's (+) terminal,....

 

[Riflejake]

Ayuh,...... The key switch should have a B (battery) terminal, red wire, 12v, all the time,.....
A S (start) terminal, yellow/ red wire, 12v only in the start position,....
A I (ignition) terminal, purple wire, 12v in the run position,.....

The Start circuit yellow/ red wire feeds the slave solenoid, to the starter's solenoid tiny terminal nearest the block,....
The tiny terminal furthest from the block, feeds battery voltage to the coil's (+), Only when Starting,....

The I (ignition) circuit, usually purple wires, feeds the electric choke, 'n the coil's (+) terminal,....

https://www.discount-marine.com/sites/default/files/comment/mercruiser_cote_moteur.pdf

This is what my wiring looks like. Only the purple/yellow resistor wire going from the choke to the coil

Edit: I now see on the diagram the purple from the alternator feeding into the choke. Duh. Will post an update shortly

 

[ROY WILLIAMS]

THE Pertronix 1146a in my MCM470 yr 1978 ....you did the no running of the engine , and the ignition key is on it . then the pertronix is the key, is 30-60 seconds , and the damaged the igniter 1146A ....
also the ignition coil did the ohm meter ...look up the YouTube ...resistor meter ....

 

[Riflejake]

Hey all, got it running - bad ballast resistor wire I think!

Ran a jumper (temporarily) from the ignition switched position to the + ignition coil and it started right up. Choke opened up to since the wire was still on the coil.

Now with the boat starting, it now also stops when you remove the key

Have the flamethrower coil coming tomorrow, will do a ballast resistor wire “delete” which should solve all issues.

Thanks for the help and guidance everyone!

 

[ROY WILLIAMS]

THE ignition coil is positive + , the ignition switch is cranking of the starter motor and the starter solenoid is the positive + of the ignition coil 12 volts , ..then engine runs , and the choke of the resistor wire is the positive + coil .. then the voltage is running around 9 volts ...
I was my ignition coil .. the ohm meter is positive - negative = 1.2 OHMS .. THEN THE SPARK COIL IS 10K OHMS OF THE NEG/POSITIVE COIL ...
also the resistor wire is 1.8 OHMS ....
THE FLAMETHROWER COIL IS POSITIVE - NEGATIVE OHM METER .6 OHMS ?