merc 4.3 shift interrupt wiring not hooked up

[boattoy]

EDIT: So i figured out the switch and the cable are OK on my 1990 merc 4.3. I started looking into the wiring (thunderbolt IV) and the white/green wire is directly connected from the distributor to the ignition "box" mounted on the manifold. Its got a diode right next to the bullet connector. There is also a white/green wire coming out of the interrupt switch then goes into the harness under the manifold and i believe it just loops around back up to almost the same spot in the back of the manifold and it has a ring terminal on it that was taped up. If i probe the wire between the diode and the box and hook it up to the white/green connected to the interrupt switch it kills the motor when i activate the switch.

my question is how does the factory wire it up? Looks like wiring was never modified. did someone not wire it right from the factory? according to the diagrams the white/green wires should all be connected. do i connect the white/green to the negative of the coil and it just grounds out the coil to kill it momentarily?

 

[wi4x4man]

Re: merc 4.3 shift cable and switch

Re: merc 4.3 shift cable and switch

what is more common when the shift interrupt switch wont cut the motor? the cable or the switch itself?

An easy way to check would be to take a multimeter set it for continuity (or if you have one that has the audible sound)and cross the two terminals on the assembly. Then, simply actuate the switch by hand. If you have continuity, then it is the cable.

Don't know about the OEM part number though. But, I have one exactly like you do in my rig.

 

[Struc]

Re: merc 4.3 shift cable and switch

Re: merc 4.3 shift cable and switch

I had a bad shift interrupt switch on my 88 Sea Ray 4.3l, and it was horrible to get in and out of gear, but it was possible, although most of the time it would jump right from forward to reverse or vice versa.

Do the continuity check that was described. It's easy, and was how I found out mine was bad. Luckily, the one on my parts boat was good, and I was able to just swap that part out.

 

[boattoy]

Re: merc 4.3 shift cable and switch

Re: merc 4.3 shift cable and switch

found out my wiring was wrong... please read first post!

 

[wi4x4man]

Re: merc 4.3 shift cable and switch

Re: merc 4.3 shift cable and switch

Sounds to me like someone didn't wire it right after the factory.

The way that mine was set up was that there was the white green wire going to the + side of the distributor. Then, there was another white green wire at that same point on the distributor that went to the shift switch. The other side of the shift switch went to ground.

So when shifting, the contact would close and cause the power to drop out for a split second thereby killing the engine for a split second.

 

[boattoy]

Re: merc 4.3 shift interrupt wiring not hooked up

I figured it out... the other green/white wire goes to the negative side of the coil. Now it kills the motor when i activate the switch. hopefully it doesnt stall the motor completely when I put it in the water next time. I pulled the cable off and it moves pretty free.

 

[Eric 3.7LX Alpha 1]

Re: merc 4.3 shift interrupt wiring not hooked up

Sometimes people disconnect the shift interruptor because it is stalling out the engine.

They think the interruptor is bad so disable it, not knowing it is probably the lower shift cable.

Good Luck, you'll know next time you take it out.