Ignition problem I think

78 Johnson 140. Was running great then last weekend it would not idle in the water but it ran on the muffs before heading out. After some messing around with it I gave up and called it a day. I found a chunk of debris in the fuel filter so I went through the fuel system for good measure and the motor seemed to be running fine. Took it back to the lake and same thing, would not idle in the water. . Will run on the muffs but not in the water.

Back at the house on the muffs it again would run ok. I checked the timing and it was spot on, checked for spark on each cylinder with a timing light and they all are firing, So I started to dig deeper. Checked the rectifier, good, checked the power pack diodes, good, checked the stator DVA at idleish 200, good. Checked the DVA input to the coils and it's only 2 volts. How could that be and the motor even run? Looked at the coils and the low side resistances are out of spec per the clymer but in spec per CDI. except for one that reads open on the high side. I think this coil has given up as the motor is missing pretty bad now.

Question is do those DVA readings to the coil make sense?

I had a hard time getting a consistent reading on one of the other coils which leads me to believe there is a plug wire issue. Am I best off to just replace all four coils as they appear to be original?

Report what you find on a compression test.

110 on all cylinders just as it was when I bought the motor which until last week would push my 24 foot pontoon with 4 adults, 3 kids and 2 coolers at 25 MPH. Motor had good power. I checked the spark while doing the compression test by inserting the plugs and grounding them. Bright blue spark but I'm still reading open on one wire so it's probably not as strong as it appears. I have never made the spark tester, maybe that is the next step, but the DVA readings out of the ignition into the coil pack is still a question.

I believe I have found the issue, a bad coil or more specifically apparently a bad coil wire. Because of the high readings I was getting on the high side of the coil I ordered four new coils yesterday and got them today, Amazon is amazing sometimes. My thought was if one had failed the others would soon be as they all look original. I replaced the coil with the bad readings, the miss went way and the motor would rev up past 5K, if I let it, with the warm up lever. I swapped that coil back in for one other that was reading ok and the miss came back. Pretty conclusive it a a bad coil.

I still don't understand the DVA readings. Some of the CDI trouble shooting guides say to check the stator output to the ignition packs across the two leads and to ground. Across the two I get 200-250 at "idle" and to ground I get 2. Same thing goes on the leads from the ignition packs to the coils. Across the two leads I get 200 but one lead to ground I get 2. Resistance to ground is really low and there is not that much current so the voltage I would imagine would be low but the "book" says it should be 150-400. dunno but it appears the coil was the culprit. Gunna change the rest and get it out on the water for a test run before trying to take the family out and being let down again.