Speaking of economics:
I like to determine if a motor is worthy of the new coils, if I am going to hold onto the motor, or if the existing coils are functional. New coils add significantly to the cost of the basic repair and I do like working on motors as much as using them periodically.
If the bendix coils measures good and only a few hairline cracks that are a distance from the central core I have had pretty good results with a several recoatings of electrical liquid tape followed by a overall covering of heat shrink. Clean the exterior surfaces before recoating since they have a waxy feel. I scape then use a electrical cleaner spray. Do not overheat the coil when heat shrinking, I damaged a couple that way. I also have repaired cracked insulation on the low voltage wires with small diameter heat shrink. So far none have failed. They always get new spark plug wires just wrapped around (and not soldered) to the high voltage terminal and that are then are laid in a bed of dielectric grease rather than the original wax in the protective rubber skirt/boot around the high voltage terminal.
I do pick and choose the bendix coils I try to fix this way. Badly cracked coils go in the garbage.
I often find that significant green corrosion on the connection at the high voltage tab to spark plug wire that might make the spark look bad.
I have been told by Bob Grubb that some of the Mercs models can get by with a weaker spark from the coils than ones with higher compression.
Timmy D mentioned to me that weak rotating magnets on Bendix ignitions have been the source of a number of weak and intermittent spark problems along with wear that messes up the point gap as you rotate the magneto advance. He also suggested to use glipto(?) instead of liquid tape since it holds up better at high voltage.
I would not bother to try this with OMC and Phelon coils.
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