Thunderbolt V gremlin HELP!!!

[J Levine]

Last week I posted about a coil arcing situation I found on my Starboard motor that went way when I swapped the coils on the engines. Well today I was not so lucky. Today I took the boat out and after 15 mins or so of cruising I started to hear a lound banging noise from the ER. I stopped the boat and check the ER and found the coil on the starboard motor again arcing between the coil output wire and the positive and negative feeds to the coil. With both motors in gear I throttled up the Starboard motor to cruise RPM and confirmed that the banging noise was comming from this engine. Kind of like a backfire or missfire. I idled back to the dock and found oil seeping out of the top of the starboard coil, I then spent the next 5 hours doing the following:

Swapped the coil wires, (again) STBD still arcs PORT is fine
Swapped the coils (again), STBD still arcs PORT is fine
Swapped the ignition modules, STBD still arcs PORT is fine
Swapped the inductive pickup sensors in the distributors, STBD still arcs, PORT is fine
Swapped the anti-knock modules, STBD still arcs PORT is fine
Swapped the knock sensors, STBD still arcs PORT is fine
Swapped the alternators, STBD still arcs PORT is fine

The motor runs fine at idle even with the arcing which is very easy to see especially in the dark.

The plugs, ignition wires, caps and rotors are all brand new MERC OEM. With the motors turned off but in the run position I checked the voltage at at the postive posts on both coils.. they were identical at about BV or 12.8 volts.

I am totally stumped. For the first time in the 6 years I have had this boat I think I may need to find a pro to look at this problem. Any of you Jersey guys that have any suggestions on a good tech please let me know. My plans to go to AC next Friday are going to get crushed if I cant get this fixed.

Anyone that has any other ideas please let me know. I know the coil that is leaking oil needs to be replaced.

Jon

 

[J Levine]

I just found this advice on the web...

"Did you know that a bad plug could cause arcing on a Thunderbolt coil?
We have customers who replace arcing coils when the only real problem
was a bad plug or plug wire."

I also found this:

"Coil Arcing- This is very dangerous, as any spark in the engine compartment has the potential to ignite flammable vapors. In most cases, the problem is not the coil ! Most of the time you will find a spark plug wire off, or a bad plug wire altogether. DO inspect the coil for cracks or carbon tracking"


This sounds like the most logical thing too me. If this is the problem I will be thrilled, yet pissed about the time I have invested in tracking this down. I will check in out in the morning.

 

[rondds]

It's all my fault.

 

[J Levine]

It's all my fault.

correct

 

[J Levine]

Well it took me about 5 seconds the morning to find the plug wire that had backed off one of the plugs and created this situation. A MAJOR case of ignoring the basics and looking for the complicated and a lesson well learned from me. Luckily this is all Ron's fault as he as already admitted for guilting me into replacing my 5 year old young plug wires over the winter.

I broke my #1 mechanical rule... if it ain't broke dont fix it.

 

[J Levine]

Yea, but at least I know all these parts are working and I now have a very in depth knowledge of their location and operation.

Maybe next weekend I can take the transmissions apart!

 

[rondds]

if it ain't broke dont fix it.

That was Rudy's philosophy until his engine portoverheated and shut down. We removed a 6 year old impeller with one vane. At least the other engine had almost 4 full vanes left, so we probably could have left it a bit longer. :smt001

 

[Tail Chaser 661]

Rule#2.... If its broke after you fixed it. Just for something to do.
Start over and check your work.

 

[J Levine]

Rule#2.... If its broke after you fixed it. Just for something to do.
Start over and check your work.

Well said and noted.

Rule #3 is "This boat was built by mortal men and can be repaired by the same"