Did my new coil die after one hour use.

[craig newton]

I have a 1984 Mercruiser 5.7L stern drive. My distributor cap contacts were green and corroded. Rotor contact looked just as bad and was seized to the shaft which was rusted. I had to cut it off. Before installing a new one, I emery clothed all the rust off the shaft. The nuts on the pos. and neg. posts on the coil were also seized in place and had to be cut off. Since I have the Thunderbolt IV ignition system I ordered the Dist. cap, Rotor and Coil recommended for this system. For a little over an hour all seemed well. A few miles shy of Catalina Isle we heard a low Pop and hiss sound and the motor died. I'm getting 12 volts to the coil so I'm thinking the system is working. No spark at all from the coil now makes me wonder if the one I received was not compatible with the Thunderbolt IV.

 

[Chris1956]

Does that motor have points or a reluctor? Reluctors have ign modules that provide the spark plug firing signal. It those contacts are as bad as the others you describe, the module may be bad.

If point ignition, maybe condenser, points or wiring is bad.

 

[craig newton]

I don't know. Would I find the module or points depending on which one I have under the rotor? Cranking it over with a test light on the + side of the coil, the light flashes on and off. Would it do that if the module was bad?

 

[Chris1956]

The rotor may or may not have the chrome disc, under it. The chrome disc has "fingers" that point down, one for each cylinder.

If you have the rotor with the fingers pointing down, that's the reluctor. Those swing thru a gap in the Sensor Assembly. The sensor assembly sends a signal into the ign Amplifer module, which fires the coil.

My '88 Mercruiser had the reluctor. One day the spark failed, and even the lousy Clymer manual I had helped me pinpoint it to the Sensor Assembly.

I would clean all the connections first, as both the sensor and amplifier are expensive. The Amplifier is listed as NLA.

 

[craig newton]

I don't know where or even what the amplifier is. Can you tell me if it is in this picture

 

[Chris1956]

The Amplifier is not shown in your picture.

 

[Scott Danforth]

in the stickies is the troubleshooting guide for the TBIV and TBV systems.