Random cutting out 4.3 mercruiser

[dalkaveli]

Long time lurker who has found the forums mentally helpful over the course of my boat Saga.

However, I am completely stumped with the issue I've been troubleshooting for a month or so and a lot of the posts covering similar issues, I have yet to see any mention of a complete voltage drop to zero on the gauge with the cutting out.

Here is my basic electrical issue: when I initially start the boat, if it sits and idles, it will occasionally just completely cut out. This will also occasionally occur at other speeds, could be under 1000 RPMs, or up to max load. What happens with the voltage gauge is it will completely go to zero, 2 to 4 seconds will go by, and then it goes right back to normal and I get the tone. It will start right up. There was a week where it was completely fine and then other times I get out and its as if I can’t even drive the boat because it’s cutting out so often.

I have not be able to pin down any significant drop in voltage throughout the ignition system. The battery is somewhat new and holds at appropriate levels, whether running or not at 14.6

Voltage across the ignition system holds steady between 14.6-14.65 at all major points.

I’ve tried bypassing the Killswitch, tried a different ignition switch, different battery cables, changed starter fuse, checked and cleaned most connections, inspected and cleaned harness pins and other connection points.

I’ve even hired a mechanic, and of course, it wouldn’t reproduce after the first stall at idle.

The only thing I haven’t checked that’s on my list is the shift interrupter switch. Just today it died two or three times at the dock in the first 15 minutes. After warming it up a bit I took it out and 20 minutes into the journey, I took a hard turn and then within 20 seconds of that turn it shut off. Could have been a coincidence. Does a faulty interruptor switch sound like it could be a cause? Other than that my only other suspicion is some random wire issue within the bundle.

Thanks for any suggestions!

 

[Scott Danforth]

You have bad connections somewhere. Start at the battery and work your way to the helm cleaning every connection with 150 grit sandpaper until they are all clean and shiny enough your mother in law would eat off them

 

[dalkaveli]

You have bad connections somewhere. Start at the battery and work your way to the helm cleaning every connection with 150 grit sandpaper until they are all clean and shiny enough your mother in law would eat off them

Thanks. I can go back over, I’ve cleaned the connections, pretty well along the ignition system. To the point where I would say, there’s no corrosion anywhere from the battery to the solenoid, to the starter to the alternator even slightly...but I can give it another pass over as I had only used electronic cleaner and a bristle brush. This is no way sounds like the switch interrupter?

 

[Scott Danforth]

When your gauge goes to zero, your feed from the ignition switch is going to zero. When that happens, your ignition is effectively off. You still have a bad connection somewhere

 

[alldodge]

key switch maybe

 

[dalkaveli]

key switch maybe

Replaced it.

 

[alldodge]

Have you pulled the 10 pin plug?

 

[alldodge]

BTW which 4.3 do you have, SN is best, but at least year and type?

 

[dalkaveli]

Have you pulled the 10 pin plug?

Yes I have. I’ve pulled it, wiggled it while running, pulled it several times, cleaned off the prongs real good. I can’t reproduce the issue by wiggling it, and nothing looks wrong with the prongs themselves.
It's a 2004, 2 bbl, TKS.
Serial is 0W317634

 

[QBhoy]

I’d check your wiring at the alternator and starter and all that. Even might run a jumper lead to make a known good earth.

 

[dalkaveli]

I’d check your wiring at the alternator and starter and all that. Even might run a jumper lead to make a known good earth.

Wiring visibly looks good at both. Voltage holds and connections are clean. I haven't tried a jumper lead yet.

 

[alldodge]

Being TKS might have an issue with the Temp switch, diode or TKS module.

Anyone of the above if it starts drawing more current, may drain power from the coil

 

[dalkaveli]

Being TKS might have an issue with the Temp switch, diode or TKS module.

Anyone of the above if it starts drawing more current, may drain power from the coil

Thanks. When you say temp switch, are the meaning the plug that screws in type by the thermostat? I'm not seeing that term in my diagrams.

Is the diode the red butt connector, or the connector at the end of the tks module itself?

 

[alldodge]

The temp is on the front of the intake and has 2 wires
The diode is most likely the Red plug. The more I think about it, its not the diode

 

[Bondo]

Thanks. I can go back over, I’ve cleaned the connections, pretty well along the ignition system. To the point where I would say, there’s no corrosion anywhere from the battery to the solenoid, to the starter to the alternator even slightly...but I can give it another pass over as I had only used electronic cleaner and a bristle brush. This is no way sounds like the switch interrupter?

Ayuh,..... What about the Ground path,..??

 

[QBhoy]

Ayuh,..... What about the Ground path,..??

Agree. Suggested running a temp

 

[dalkaveli]

Ayuh,..... What about the Ground path,..??

I can see about doing a temp or measuring resistance. Everything is grounded at block, 5 or so wires. When I replaced the negative battery cable as a test, I did see one random green 10 gauge ground wire attached to block that was not connected to anything else... which is interesting. I probably should just remove that entirely. Appreciate all the suggestions.

 

[alldodge]

Green wires are Bonding wires and normally go from a ground buss bar to each thru hull fitting.

 

[dalkaveli]

Green wires are Bonding wires and normally go from a ground buss bar to each thru hull fitting.

so this is that green wire and there’s no busbar anywhere within the range that this could connect to. It’s just at the block with the rest of the grounds. Pretty weird huh?

 

[alldodge]

Added by PO for some reason and may have been for the problem your getting. Might have used Green because it would standout and also so it would be known as ground.