early 70's Mercury 650

catmotorhead · Apr 11, 2013

Every time I hit the key she fires and the starter disengages but it only fires 1 time then I have to turn the key again. Good spark on the plugs and fresh gas in the tank. Timing issue???
thanks
charley

catmotorhead · Apr 11, 2013

Re: early 70's Mercury 650

I also hear a clicking sound when I turn the key on and off but when I unhook the green wire from the coil it goes away.

Laddies · Apr 11, 2013

Re: early 70's Mercury 650

Sounds like a bad ign switch, first make sure you have 12 volt to the red terminal on the switchbox then try a jumper wire between the red terminal and the white terminal on the box and see if it stays running. Use the test info that I gave you earlier and you will find the problem.

Laddies · Apr 11, 2013

Re: early 70's Mercury 650

The arcing your hearing is the coil firing caused by the voltage surge when it is disconnected or the key is turned on and off that the why it works, it stops when you take the green wire of the transformer (coil) because that what you hear arcing, if you turn the engine to TDC on any cyl and put a plug in the wire it will fire that plug if you turn the key on and off.

catmotorhead · Apr 11, 2013

Re: early 70's Mercury 650

I have 12v at the red wire but I don't have 12v at the white wire when the key is on

Laddies · Apr 11, 2013

Re: early 70's Mercury 650

Then you have a bad wire, switch or the plug in needs to be cleaned and the male ends spread slightly. See if it runs with a jumper on the system

catmotorhead · Apr 11, 2013

Re: early 70's Mercury 650

nothing happens when i jumper no clicking everything is dead now but i still have 12v on the switch box from the red wire

Laddies · Apr 11, 2013

Re: early 70's Mercury 650

You need to go to the CDI sheet I posted before and do the test for no spark on any cyl. It does not even require any special tools and take about 10 minutes it has never failed us in 25 years.

catmotorhead · Apr 15, 2013

Re: early 70's Mercury 650

ok so now i have a fully charged battery and clean tight terminals. I tested the coil as the diagram said and I get spark as i tap the ground. Then i aligned the rotor to test my individual plug wires and I do get spark on each wire its lined up on. I jumped the red and white wires together (even though when the key is on I have 12v on the white wire) and i try starting the motor its fires up every time i hit the key but dies as soon as the starter disengages. I still hold the key on like I'm starting it. According to the guide it says my trigger is bad. I don't understand why The starter being engaged makes a difference. gas spark oxygen and compression this motor should run.

Laddies · Apr 15, 2013

Re: early 70's Mercury 650

If you have the same problem with the key on and the jumper wire red to white then the trigger is bad, the test with the jumper wires shows you that the switch box, coil, cap and rotor are all working, so that leave low or no voltage to the white terminal, the switch or a wiring problem or a open in the trigger, then you arc the system you are bypassing the trigger by causing a voltage flux in the system and thats what the switchbox senses when it fires the coil.

catmotorhead · Apr 15, 2013

Re: early 70's Mercury 650

so thats the coil fireing 1 time and the reason it fires up and dies as soon as the starter disengages?!

Laddies · Apr 15, 2013

Re: early 70's Mercury 650

I think that the switchbox is sensing the voltage flux from the starter ingaging and firing the system once, is what is causing your problem and the trigger is not working at all, you could prove this by turning the engine with a starter rope and the key on checking for spark I believe but have never tried it myself.

catmotorhead · Apr 15, 2013

Re: early 70's Mercury 650

It definetly only runs when the starter is engaged but when i unhook the trigger wires it does nothing. no fire at all

emckelvy · Apr 15, 2013

Re: early 70's Mercury 650

Good Idea; just pull all the spark plugs, stick 'em back in their boots and lay them so the plugs are grounded to the block.

Turn the ign to "ON" (or jumper together the red & white wires on the same side of the switchbox), and pull the motor over with a rope on the flywheel.

If it's gonna spark, it'll definitely do so. You could also undo the distributor belt from the pulley and spin the dist. shaft in either direction, but roping it over is a lot easier.

Let us know what you find..........ed

catmotorhead · Apr 15, 2013

Re: early 70's Mercury 650

Is there something else that could be damaging the trigger or causing it too malfunction or do they just wear out? I want to be sure so when i put yet another distributor on it don't wreck it by mistake

Laddies · Apr 15, 2013

Re: early 70's Mercury 650

With the wires hooked up, connect a voltmeter to the red terminal you should have 12 volts all the time, then to the white terminal turn the key on you should have 12 volts, if you don't the switch is bad or the wireings bad. With 12 volts on the white terminal leave the voltmeter hooked up and try to start the engine if you lose the 12 volt reading before you turn the key to off you have a problem with the voltage supply, so hook the jumper wire up between the red and white terminals and see if it will stay running if it does that will tell you that the problem is in the wiring not the engine, if it don't help your back to a bad trigger.

Faztbullet · Apr 15, 2013

Re: early 70's Mercury 650

The trigger is defunct replace it.......Synonyms for defunct
dead - deceased - departed

catmotorhead · Apr 15, 2013

Re: early 70's Mercury 650

i want too be sure i dont ruin another one if in fact i did something to ruin this one. I believe its "defunct"

Laddies · Apr 15, 2013

Re: early 70's Mercury 650

I don't think you ruined that one, about the only way to ruin it would be to hook the wires up wrong and hit it with revesed polarity or reverse the battery leads, once I found a battery that was charged backwards on a unit that fried 2 triggers.

Faztbullet · Apr 15, 2013

Re: early 70's Mercury 650

Disconnecting battery leads while running will kill one in a heartbeat also.......

early 70's Mercury 650

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