Boat has 1995 4.3LX engine with Thunderbolt IV [4bbl carb w/ electronic ignition].
Typical senario: engine starts and runs fine but after about 15 minutes at moderate cruising speed it shuts down. I've already confirmed that there is no spark when this happens. The engine will restart but usually not after a half dozen attempts. When it does restart, it's strong and smooth. If I run it long enough, it will probably shut down again but sometimes it doesn't. Had this problem occur once from a cold start but all other times it's during a cruise. Initially I thought this was a fuel related problem but it's not. I changed the coil with a new one but the problem still exists. Took off the sensor and the ignition amplifier. Other than checking for cracks at the sensor jumper leads, the Mercruiser book doesn't provide any troubleshooting or inspection procedures for the IV [of course there is a complete troubleshooting diagram for the Thunderbolt V system]. The sensor is questionable. There is some rusting at the metal leads and pitting at the sensor tip. Not sure what I can do to inspect the amplifier. There was thermalconductive grease behind it as required. I suspect that I'm getting some sort of thermal breakdown. The wire leads going to the distributor all seem OK. I'm going to recheck the neutral safety switch and the ignition switch.
Question: could either the sensor or the amplifier cause intermittent type spark loss problems?
Is there a way to check/bench test the amplifier such as resistance reading?
Typical senario: engine starts and runs fine but after about 15 minutes at moderate cruising speed it shuts down. I've already confirmed that there is no spark when this happens. The engine will restart but usually not after a half dozen attempts. When it does restart, it's strong and smooth. If I run it long enough, it will probably shut down again but sometimes it doesn't. Had this problem occur once from a cold start but all other times it's during a cruise. Initially I thought this was a fuel related problem but it's not. I changed the coil with a new one but the problem still exists. Took off the sensor and the ignition amplifier. Other than checking for cracks at the sensor jumper leads, the Mercruiser book doesn't provide any troubleshooting or inspection procedures for the IV [of course there is a complete troubleshooting diagram for the Thunderbolt V system]. The sensor is questionable. There is some rusting at the metal leads and pitting at the sensor tip. Not sure what I can do to inspect the amplifier. There was thermalconductive grease behind it as required. I suspect that I'm getting some sort of thermal breakdown. The wire leads going to the distributor all seem OK. I'm going to recheck the neutral safety switch and the ignition switch.
Question: could either the sensor or the amplifier cause intermittent type spark loss problems?
Is there a way to check/bench test the amplifier such as resistance reading?