Key would not shut off then wouldnt restart.

[vupilot]

Motor is a 1975 Merc 402 40hp with Mercontrol.

I was test running the motor in the driveway on muffs. It started and ran fine then warmed up and was idling high so I wanted to make an adjustment so I shut the key off but the motor did not die. I started wiggling wires and when I pushed on the big main harness that plugs into the outside of the motor lower case it died.

But then it would not restart, no cranking, not even a click. Wiggled the same wore harness, nothing, wiggled, the Mercontrol lever in and out of gear, nothing, wiggled the wires going to the ignition, and the main harness again and it started right up. I tried to wiggle things and reproduce the problem but it never came back.

I have had instances in the past when it would not crank and I just wiggled the MerControl in and out of gear and back to neutral and it started. I'm wondering if its the safety switch or could it be something else.

Thx

 

[vupilot]

Re: Key would not shut off then wouldnt restart.

OK so I wasn't able to reproduce the problem after it happened yesterday but I just went out to the garage and turned the key and nothing happened! Pushed in on the big harness where it plugs into the side of of the motor case and it turned over just fine. So perhaps its a connection problem right there.

How do I go about fixing that and making a more positive connection? I tried ever so slightly bending some of the prongs to give more friction and a tighter fit but Im sure that will only help slightly. Whats the best fix?

 

[ctiggemann]

Re: Key would not shut off then wouldnt restart.

OK so I wasn't able to reproduce the problem after it happened yesterday but I just went out to the garage and turned the key and nothing happened! Pushed in on the big harness where it plugs into the side of of the motor case and it turned over just fine. So perhaps its a connection problem right there.

How do I go about fixing that and making a more positive connection? I tried ever so slightly bending some of the prongs to give more friction and a tighter fit but Im sure that will only help slightly. Whats the best fix?

I had a 70HP Merc 1978 that I ended up replacing the wiring harness on the engine side. I also cleaned the connectors on the boat side and did as you did in pinching them together a little to get a tighter fit. You could get some electrical grease from an auto parts store. They sell it in little packets for light bulb sockets. That will help with corrosion and should help with wear.

 

[matt167]

Re: Key would not shut off then wouldnt restart.

may have a spring in the plug to hold it in ( my '64 650 does ). Don't know what more you could do other than dielectric grease to help hold it in.

 

[Texasmark]

Re: Key would not shut off then wouldnt restart.

The problem with the wiring harness makes no sense to me. The black yellow striped wire, Pin 1 on the Commander 2000 control's 8 pin wiring harness, hence 1 on the engine, is the engine kill wire. The ignition switch in the control box grounds that wire when you turn the switch to OFF. The ground is wired to the ignition modules via pin 1 and thereby shorts out the triggers thus killing the engine.

Once you try to restart and leave the OFF position, the ground is supposed to disappear allowing the trigger circuits in the CDI modules to fire the plugs and allow the engine to start.

My bet is that you have a bad ignition switch. A bad connection as described surely can cause the former but not the latter.

Mark

 

[GA_Boater]

Re: Key would not shut off then wouldnt restart.

Sure it makes sense. The side connector is not making good solid contact on two of the pins, the kill pin causing no ground for shut off and the start pin causing no 12 VDC to the solenoid.

Probably a combination of problems with the connector - dirty, male pins are not seating in the female side or the connector halves are not completely mated.

Look at the male pins, they are split. If one of them is split wider than the rest, what could be happening is the wide one is straddling the side of the female connector keeping the two plugs from fully mating. It happened to me.

 

[Texasmark]

Re: Key would not shut off then wouldnt restart.

Sure it makes sense. The side connector is not making good solid contact on two of the pins, the kill pin causing no ground for shut off and the start pin causing no 12 VDC to the solenoid.

Probably a combination of problems with the connector - dirty, male pins are not seating in the female side or the connector halves are not completely mated.

Look at the male pins, they are split. If one of them is split wider than the rest, what could be happening is the wide one is straddling the side of the female connector keeping the two plugs from fully mating. It happened to me.

Well that makes sense being ground from the engine to the key switch is via pin 4 of the connector on the black wire.

So I will go with the flow. Clean up the connector.

Mark