I have an older Honda 7.5, likely 25 years old or so, but with very little use in at least the past ten years. I'm having a bear of an ignition problem that is driving me crazy. All signals seem ok, and I'm using an oscilloscope to observe them, not a simple voltmeter. But I have a very weak spark with the plugs out of the cylinders, only visible in a darkened room, and no spark with the plugs in the cylinders trying to fire into a compressed mixture. (I can see a difference in the waveform of the signal driving the ignition coil when they fire vs. not fire.)
There are only four components, total, in the ignition system - a magneto coil that generates the operating power, an exciter coil that generates a trigger pulse, an electronic-ignition module aka capacitor-discharge module, and the ignition coil that makes the spark. My best guess is that the problem is in the electronic-ignition module, specifically a capacitor in the module that has lost some of its ability to hold a charge. That module is potted so I don't have access to the individual components making up the module. Otherwise, it would be an easy diagnosis.
My problem is that each of the four components is expensive, well over $100 for the electronic-ignition module and almost that for the spark coil. I'd be glad to buy a new part if I had complete confidence that it would solve the problem, but after two days of chasing ghosts I don't have that confidence. That's why I'm asking for help.
Does anyone here have an old 7.5 or 9.9 that has failed for a non-ignition reason that they would be willing to part out?
Anyone with experience to confirm or contradict my guess?
I should add that two weeks ago the engine was submerged in salt water for about an hour but I got it running again within an hour after a fresh-water flush, compressed-air dry and oil change. Ran fine for a couple of hours thereafter.
The season is passing quickly. I've had my boat in since the first week of May and used it exactly twice. Please help.
Thanks,
Bill
There are only four components, total, in the ignition system - a magneto coil that generates the operating power, an exciter coil that generates a trigger pulse, an electronic-ignition module aka capacitor-discharge module, and the ignition coil that makes the spark. My best guess is that the problem is in the electronic-ignition module, specifically a capacitor in the module that has lost some of its ability to hold a charge. That module is potted so I don't have access to the individual components making up the module. Otherwise, it would be an easy diagnosis.
My problem is that each of the four components is expensive, well over $100 for the electronic-ignition module and almost that for the spark coil. I'd be glad to buy a new part if I had complete confidence that it would solve the problem, but after two days of chasing ghosts I don't have that confidence. That's why I'm asking for help.
Does anyone here have an old 7.5 or 9.9 that has failed for a non-ignition reason that they would be willing to part out?
Anyone with experience to confirm or contradict my guess?
I should add that two weeks ago the engine was submerged in salt water for about an hour but I got it running again within an hour after a fresh-water flush, compressed-air dry and oil change. Ran fine for a couple of hours thereafter.
The season is passing quickly. I've had my boat in since the first week of May and used it exactly twice. Please help.
Thanks,
Bill