resolving ignition issues on a mercury/mariner inline 6 tower ADI
just a little pointer on how to diagnose missing spark from cylinders on these engines.
top cylinder is #1.
any electrical problem: remove all connections from terminal and use electro cleaner and fine grit sanding paper to remove any corrosion. pay special attention to ground connections. confirm working spark plugs and spark leads before proceding.
be aware of the fact that a spark might not show up on your timing light as the spark leads are shielded, so do a visual inspection for spark. results may vary with the quality of the timing instrument.
always check all 6 coils for consistent voltage output between + and - terminal to confirm results.
no spark on 1, 3 and 5: faulty upper switchbox
no spark on 2 4, and 6: faulty lower switchbox
no spark on 1 and 2 : faulty trigger assembly, coil 1.
no spark on 3 and 4 : faulty trigger assembly, coil 2.
no spark on 5 and 6 : faulty trigger assembly coil 3.
for all errors including two consecutive cylinders measure Ohm between Red/pur/white yellow sleeve wires and Red/pur/white without yellow sleeves. you are supposed to find 3x ~1500-1800Ohm if trigger assembly is working. if only 2x is found, replace trigger assembly.
missing spark on single cylinder: defective coil. measure voltage from + to - on coil to check for consistent readings.
make sure to use a quality electrical measuring instrument.