5.7 Alpha 1 thunderbolt 4, randomly shut off at cruise

[Biggyniner]

Hey all,

Have a 93 Ciera 2655 with an early alpha 1 gen 2 outdrive and a new (13 hours on it) 5.7. Full closed loop cooling.

Today I was running it at cruise ~3400 RPMs and planed out. Suddenly she lost power and stalled. Reset the shifter to N, cranked it and she fired right up. Got it going right back up to cruise and headed for the dock, worked fine. I had been running at low speed and high speed for about 1.5 - 2 hours prior to the stall - no hiccups nothing... This stall was super random. I have my kill switch/lanyard bypassed so it was not that. Boat has a new (sierra) coil for the Tunderbolt 4 ignition, new edelbrock marine carb as well as the latest trigger assembly in the distributor. New plugs (new freaking engine).

Any ideas?

 

[alldodge]

Lost power to the coil would be my guess. So that's everything from the bat to the coil (wires, key, connections)
Could also be tach wire grounding

 

[Biggyniner]

Lost power to the coil would be my guess. So that's everything from the bat to the coil (wires, key, connections)
Could also be tach wire grounding

I'm going to go down to the marina and check the connections today.

My other thought was maybe the ignition control module starting to go? I feel like it would be more problematic if that was the case, unless these are very early symptoms... Does anyone have any experience with the replacement ICM for the Tbolt 4 like this:

 

[tank1949]

with friend at controls and boat idling, start wiggling motor wires. It might be best to purchase some good rubber gloves. I suspect corrosion or ground NOT making good contact. If salt water used boat, I'd more than suspect it. Copper and saltwater do not play well together.

 

[alldodge]

Before I would go from a TB4 to TB5 conversion I would change to Delco EST

That said, I don't see the TB4 going out and back on, its a bad connection

 

[Biggyniner]

Before I would go from a TB4 to TB5 conversion I would change to Delco EST

That said, I don't see the TB4 going out and back on, its a bad connection

Sounds good - I have not been able to get back out to the marina, but maybe tomorrow. I will check and play with wiring at ignition and coil.

Regarding the above module, I did not realize that was a TB V conversion. It showed that part number as the replacement module for the TB IV since those are discontinued...

 

[dubs283]

new (sierra) coil....latest trigger assembly in the distributor.

is the ignition sensor a sierra brand as well?

never had much (good) luck with sierra electronic parts

 

[Biggyniner]

Figured it out. The main harness plug at the engine was barely on. I had it running and I touched it and it died. Pushed it on all the way and secured it with the hose clamp.. Pretty sure that was the cause.

 

[NHGuy]

Thanks for reporting back. Your post will help someone in the future.

 

[Biggyniner]

Thanks for reporting back. Your post will help someone in the future.

Totally. Always frustrated when you are reading through a thread and there is no resolution