four winns 214
Senior Chief Petty Officer
- Joined
- Oct 25, 2008
- Messages
- 769
Engine: 1984 Merc 228R Serial #6726322 Thunderbolt IV Ignition
I've owned this boat 11 years and it's never let me down in over 2,000 miles of river and lake cruising. A few nights ago coming in from a Kentucky Lake sunset cruise, the engine started to stumble and miss. The missing was displayed on the tach by 100-300 rpm oscillations. The engine kept running, thankfully, and got us back to Moors Resort.
The next day, I changed the fuel/water separator filter and dumped the contents of the old one into a clean glass jar. Not a speck of water was apparent. I changed the inlet filter to the Rochester Quadrajet carburetor. It was clean.
I tried new plugs. No joy. Then I took a shotgun approach and changed cap, rotor, sensor, coil, and plug wires. I thought that was the fix. I ran it for 20 minutes at 3,000-3,400rpm from Moors to Duncan Bay. It ran like a top. On the way back, at 3200rpm, the missing started all over again EXACTLY like it had done previously. I was deeply disappointed.
This problem seems to be heat and load related. Pull the throttle back and the missing stops, but a small tic in the tach display can be seen.
I'm going to look at the wires coming from the ignition module next. This boat is 33 years-old, so maybe it's a wire breaking down.
I'm fairly certain the Thunderbolt IV ignition module is original. Is it possible that the module is failing? It's been my understanding that the module either works or it doesn't with no in between. Is that not the case?
I've owned this boat 11 years and it's never let me down in over 2,000 miles of river and lake cruising. A few nights ago coming in from a Kentucky Lake sunset cruise, the engine started to stumble and miss. The missing was displayed on the tach by 100-300 rpm oscillations. The engine kept running, thankfully, and got us back to Moors Resort.
The next day, I changed the fuel/water separator filter and dumped the contents of the old one into a clean glass jar. Not a speck of water was apparent. I changed the inlet filter to the Rochester Quadrajet carburetor. It was clean.
I tried new plugs. No joy. Then I took a shotgun approach and changed cap, rotor, sensor, coil, and plug wires. I thought that was the fix. I ran it for 20 minutes at 3,000-3,400rpm from Moors to Duncan Bay. It ran like a top. On the way back, at 3200rpm, the missing started all over again EXACTLY like it had done previously. I was deeply disappointed.
This problem seems to be heat and load related. Pull the throttle back and the missing stops, but a small tic in the tach display can be seen.
I'm going to look at the wires coming from the ignition module next. This boat is 33 years-old, so maybe it's a wire breaking down.
I'm fairly certain the Thunderbolt IV ignition module is original. Is it possible that the module is failing? It's been my understanding that the module either works or it doesn't with no in between. Is that not the case?
