The last several times out, with my boat, the engine began to act up right to the point of dieing and not restarting. It would not even completely turn over on restart trys. It was obvious there was an ignition breakdown so amidst tossing waves, I pulled the engine cover, removed the distrib cap and found a black build up on the rotor strap, under the center spring loaded coil terminal contact.
Scraping of the black residue, the motor would fire right up. Not knowing exactly what was going on, I ordered a new cap and rotor. First off I noticed that the Napa rotor was about .020 taller than my previously used Pertronix supplied rotor. That got me to looking closer.
I looked closely at the cap and there was a faint black track around the inside sidewall, a considerable distance below the bottom of the cylinder contact studs. I cut a hole in the top of the old cap, between the #8 cylinder tower and the primary coil wire tower. This is what I observed and subsequently measured.
No wonder I was having a problem. Not only was the top of the rotor backstrap .092 below the bottom tip of the cylinder terminal studs, the center contact was probably not making firm contact with the rotor. This of course would cause arcing which would account for the black deposits on the rotor strap.
I have temporarily made changes that will probably work, but they are still not right. The tip of the rotor should be riding right up in the middle of the flattened off cylinder terminal.
I just cannot figure out what the deal is. This is an old Prestolite mechanical advance marine distrib. I used it for years and only recently installed the pertronix unit. But that would have absolutely nothing to do with the dizzy shaft height and subsequently the rotor height.
I just post this for general interest as I really doubt anyone has a solution. I also doubt that many people have done measurements or cut holes in the top of their caps to see where their rotors are riding.
The only possibility I can think of is that the Napa Marine caps and/or rotors are not of the proper dimensions.
Scraping of the black residue, the motor would fire right up. Not knowing exactly what was going on, I ordered a new cap and rotor. First off I noticed that the Napa rotor was about .020 taller than my previously used Pertronix supplied rotor. That got me to looking closer.
I looked closely at the cap and there was a faint black track around the inside sidewall, a considerable distance below the bottom of the cylinder contact studs. I cut a hole in the top of the old cap, between the #8 cylinder tower and the primary coil wire tower. This is what I observed and subsequently measured.
No wonder I was having a problem. Not only was the top of the rotor backstrap .092 below the bottom tip of the cylinder terminal studs, the center contact was probably not making firm contact with the rotor. This of course would cause arcing which would account for the black deposits on the rotor strap.
I have temporarily made changes that will probably work, but they are still not right. The tip of the rotor should be riding right up in the middle of the flattened off cylinder terminal.
I just cannot figure out what the deal is. This is an old Prestolite mechanical advance marine distrib. I used it for years and only recently installed the pertronix unit. But that would have absolutely nothing to do with the dizzy shaft height and subsequently the rotor height.
I just post this for general interest as I really doubt anyone has a solution. I also doubt that many people have done measurements or cut holes in the top of their caps to see where their rotors are riding.
The only possibility I can think of is that the Napa Marine caps and/or rotors are not of the proper dimensions.
