ignition module systems

[tystick]

what are the symptoms of a tempermental ignition module?

i have a issue where the boat starts and runs fine but when returning to dock and idle will stall and refuse to start until later when cooled down then will start again

mechanic said this sounds like the merc ignition module is failing which has been a well known issue


1990 4.3L merc thunderbolt 4

 

[off course]

Re: ignition module systems

WOW I can't believe someone else has the same problem as I do.My '99 5.0 mercruiser does the same thing. I recently rebuilt engine and alternator, problem surfaced after this.The engine runs fine all day until you idle, usually in gear, such as you would do returing to the ramp or trolling.I hope it's not the ignition module, mine cost $400.good luck if I figure my problem out I'll post a reply

 

[OH3477CH]

Re: ignition module systems

My Thunderbolt IV is 20 years old and has never given me trouble, but I do replace the expensive pick-up in the distributor every couple of years. This is mostly because I am by nature a nervous type (single engine boats on Lake Erie can do this to you) and I have a decent amount of money to waste on my stupid boat.

Your problem sounds like a carb issue. The carb is temp-sensitive, the ignition is not (unless you get it REALLY hot, when it totally craps out and doesn't recover). You probably have some build-up in the primary jets or the idle air adjustment is not correct. Does it make a difference how hard you throttle back? In other words, if you back down hard and it dies this would lead me to the idle air, if it just dies no matter how easy you back down I would look at the jets.

 

[WAVENBYE2]

Re: ignition module systems

Try this.

 

[tystick]

Re: ignition module systems

"Per Mercury's data the Module, Hall effect sensor, and coil all fail equally."

the thermoconductive grease that is recomended indicates it is temp. sensitive and maybe mine needs it.
I am in a remote area so would be hoping for any alternative to this.

the module is not the expensive part (relative) around $40 - it is the amplifier on the thunderbolt IV which is expensive
I am not sure that it is a carb issue / fuel issue but will have to wait until it happens again to do more testing as it is only a tempermental condition.

 

[tystick]

Re: ignition module systems

bump

 

[tystick]

Re: ignition module systems

after reading archives, I am surprised that I have not read more of this symptom as I am hearing that it is a common mercruiser issue but the thunderbolt may be different


is there any way to jump a bad module and/or coil if needed?