I recently re built my 1976 25HP Johnson. It was running well, but I decided to change the coils. The coils that were on there were not that old, but the plug wire kept coming off where it attaches to the coil. Anyway, I got two new Sierra brand coils, and tried it. It runs, but spits and acts funny. I took the cover off, and notice the boot on the top cylinder looks charred right where the boot ends and you can see the porcelain. I took the plugs out and found that the spark didn't always fire, I also noticed an arc from the charred spot. What gives? The boots were on by the manufacturer, and the plugs are new. I guess if it aint broke don't fix it. Looking back I should have glued the wires into the old coil.