1996 7.4l Merc. motor dieing at unpredictable times--**SOLVED***

I have a 1996 7.4L Mercruiser motor with Thunderbolt V ignition.

The boat will start fine. Idles fine. Runs under all conditions.

While on the muffs in the driveway or at the lake in-gear or out of gear the boat will suddenly and unpredictably die. It doesn't die after a certain amount of predictable time, it may die after 30 seconds or 2 hours.

If I try to restart from the run key position the boat will NOT start under any circumstances. If I turn the key switch to the completely OFF position and then re-start it fires up immediately. It will then run for an unpredictable amount of time before it dies again.

I have already done the following:

1--Cap/Rotor
2--Plugs/wires
3--Rebuilt Carb
4--Fuel Pump and fuel filter replaced
5--Pick-up and air vent tubes are clear at fuel tank.
6--Slave Solenoid new
7--Kill Switch at throttle bypassed.
8--Neutral switch bypassed
9--oil sending unit check ok
10--Tach. checked out ok
11--ignition key switch checked out ok.

The things I have left are Knock Control Module; pick-up coil; and ignition module.

I took it to a boat shop and they couldn't solve the problem at all.

What am I missing??


It was definitely the Ignition Module. $486.00 later and the boat works perfectly.

Water was running from the swim platform onto the air-cleaner shroud and onto the old module.

Thank the light.
Thanks

Re: 1996 7.4l Merc. motor dieing at unpredictable times

Re: 1996 7.4l Merc. motor dieing at unpredictable times

And the main harness plug for corrosion or looseness. Should have a hose clamp on it too.

Re: 1996 7.4l Merc. motor dieing at unpredictable times

Re: 1996 7.4l Merc. motor dieing at unpredictable times

It has a zip tie on it now. It isn't corroded and appears tight. I opened the spacing of the male side of the plug with a small screwdriver, which did tighten the connector up. I will put a hose clamp on it today.

I thought it could be a loose or corroded main harness, but it will die on muffs in the driveway without any bouncing. There isn't rhyme or reason behind the dying.

Since I have to "reset" the ignition to get it to restart, I'm thinking its electrical in nature. If it were the Carb, or fuel problem I wouldn't have to turn the key switch to the completely off position to get it to restart, I could simply restart it from the "run" position on the key switch.

It acts like it is getting "no spark" after it dies and I'm trying to restart it without turning the key switch completely off.

Is there anything BESIDES the Ignition Module or Knock Control Module that could create this problem?