Mercruiser 4.3 V6 starting issues

[Docmij]

Hello all. I need some help. This past spring, I bought my first boat, a 91 Celebrity 180CX. It has a Mercruiser 4.3 V6 I/O. Took the boat out several times this past summer and really enjoyed it. On my second to last trip out, the boat ran fine all day, but after about 6 hours on the lake and starting to head in, it started loosing power. Got it in and changed out the plugs and wires before next outing. On the last trip out, ran boat for about same amount of time and when we started to head in, same issue, only this time it shut down and had to be towed in. Brought it home and started checking possibilities. Boat will not start. No fire from coil. Changed out coil, nothing. Changed out ignition control module, nothing. Pulled wire from dist cap and checked to see if coil would fire, nothing. Checked emergency shutoff switch, and it tests fine. Engine reset button will not engaged, which tells me it hasn't been tripped. Now I'm running out of time and ideas. Need to get boat started to winterize it. Really need guidance.

 

[niceoldgrady]

You have any access to a schematic? Almost sounds like some sort of switch / interlock missing. Owner's manual might have a schematic illustrating everything external to engine.

 

[Bt Doctur]

do you have 12v at the + side of the coil with the key on?

 

[kmarine]

You may want to check the ignition module or see if your boat has points which could have a bad condenser. I would also double check the fuel water separator as it is part of winterizing

 

[Docmij]

As of right now, I do not have access to a schematic or owners manual, but I will continue to look into that.
As for voltage at coil terminals, i do have +12 VDC on coil terminals with key in ignition and on. I also tried to connect directly to the coil + terminal from the battery and still had no fire form coil when trying to start.
Ignition module was just replaced with a sealed solid state module. I will check into the condenser and fuel water separator.

Thanks to everyone for your input. It is greatly valued and appreciated.

 

[Bt Doctur]

Ignition module was just replaced with a sealed solid state module. I will check into the condenser and fuel water separator.
You should have the Thunderbolt IV system and it needs its own module, not a generic replacement
condenser is used in a points system
water sep has nothing to do with the spark
A bad tach will kill spark also.
a engine serial number would help get the correct manual