Ignition interrupt switch

[boonjy]

I have a 94 Chris Craft with a 5.8L 351 Ford w/carb and an OMC Cobra outdrive. My ignition dies after running the boat for about 30 minutes or so. It will be intermittent at first (while at full throttle it will just abruptly die, then restart without any problems) but after awhile it dies and will not restart.

I suspect the ign interrupt switch. A few questions for those more familier:

How does the switch operate?

Is it located on the shift lever? (a spring loaded arm on a black box with 2 wires)

How do I test it?

Can it be thermally affected? (which would explain why it only dies when warm)

Where can I find a wiring diagram that includes it? I have a Seloc OMC manual, but none of the diagrams include it.

Thanks for the help!;

 

[fgardinier]

Re: Ignition interrupt switch

My understanding of the interrupt switch is that it is used to reduce the power from the engine to allow easier shifting. It should be located on the shifting cable. Your decription of the black box sounds right. It should only be a simple micro switch that is activated when you shift drive gears. I would not suspect this to be the culprit. It is a simple on/off switch that leads to a module somewhere that controls the engine. My first suspect would be the coil. When the engine is running fine shut it down and place a meter between the wire from the distributor to the coil and crank the engine. there should be a swing of low to high voltage. <5 volts to 12 volts. This will tell you what it is when everything is normal. Then when the engine dies and will not restart check it again. If it is still working the interrupter circuit is fine. Then remove a spark plug wire on one of the cylinders and connect a spare plug. Make sure you can see if there is a spark. The edge of the plug must touch the engine for a grounding point. If it sparks while cranking it over, it should not be an ignition problem. If it does not spark replace the coil. Hope this helps.

 

[JAK II]

Re: Ignition interrupt switch

I had a similar problem this summer with my CC 22 Launch It would run out and than just die sit for a minute and you would take off only to die 300 yards down the lake, I went crazy trying to figure it out, it turned out to be the low-pressure fuel pump. Have you checked your fuel pump yet? If not I would pull the pump and have it tested, that might be your trouble.

good luck with it