4.3 cut out... won't stay running?

[gtfireftr]

So I was out today to try to figure out if I have an issue.... I was out last week and I seemed to loose rpm, and speed (about 200 rpm, and 2 mph). It was rough out, and I had a load on, so I thought that may be the issue.
Fast forward.... I went out, and found that she was still a bit sluggish....then on plane about 3600 rpm the port motor started cutting out.... it went from 3600-0 rpm, then up to 2000, then just died... I could get it to restart, but then died again....I kind of figured it was an ignition issue... loosing spark intermittently. I had a coil, and ignition sensor, so I changed them one at a time with no change... ugh.... So I limped home on the starboard engine...
I verified that spark was my problem... I got a spark tester and I could see that I was loosing spark and the engine would die....I was a bit paranoid, so I did a compression check....
I think the numbers are ok, but hopefully someone will verify this for me.
#1 170, #2 160, #3 170, #4 160, #5 170, #6 165....
Anyway, I was considering swapping to a gm electronic ignition system and eliminate the Tunderbolt 4....I was getting ready to order this, but I decided to double check everything first.... I found the main wire off the alternator completely disconnected...Well, I didn't think that this could be the issue, so I repaired the wire to the alternator, and low and behold that was the problem..... I don't know why this would cause this issue....
Can someone please explain this if possible......
Maybe voltage drop to ignition system???
TIA

 

[gtfireftr]

Anyone???

 

[av8ingtom]

Your ignition system uses current from your battery and your alternator charges the battery. With all the electrical stuff on your boat using this electricity it will cause a very weak power supply to your coil and spark plugs. It will loose RPM's as you said, and the engine will shut down. Can not explain why only one engine shut down. Did the wire melt or was it just a bad connector

 

[dwna1a]

Sounds like the ICM has gone bad. Does it have a Thunderbolt System?

 

[gtfireftr]

Thunderbolt 4.

 

[scoflaw]

T. bolt 4 is a Gm ignition. If any of those parts go south, all is available at the local NAPA or Autozone. Mid 80's gm parts.

Voltage needs to be up to snuff to work properly. Sounds like your problem is resolved.

 

[gtfireftr]

T. bolt 4 is a Gm ignition. If any of those parts go south, all is available at the local NAPA or Autozone. Mid 80's gm parts.

Voltage needs to be up to snuff to work properly. Sounds like your problem is resolved.

I think you are correct with the problem, but I am very skeptical to go out for any length of trip.....
I was thinking of swapping to a gm voyager ignition which eliminates all the modules and sensors and excessive wiring from the distributor.

 

[scoflaw]

t bolt 4 is a solid setup, parts are available and cheap. Now if you had an old style point system, sure.