1974 Mercury 500: Thunderbolt ignition replaced with magneto

[rdc1280]

I am new to this engine, having just bought it "recently running, although weakly." I opened it up and attempted to do a link and sync, but discovered that the Thunderbolt switchbox was disconnected and the ignition driver had been replaced with a magneto unit (from a manual start motor?) and was set up to run. It does fire, and I used a timing light to find the advance: around 10 degrees BTDC is the lowest possible before the magneto bumps against the lower carb, and the optimal max advance (34 degrees) happens before the adjustment screw can reach.

Now the questions: is this repairable? Is there a way to adjust the innards of the magneto or how it mounts so it is within reach of the adjustors? Has this swap been done successfully before?

If pics are needed just say the word, my camera is charging.

Thanks, Riley

 

[rdc1280]

Re: 1974 Mercury 500: Thunderbolt ignition replaced with magneto

Anybody? I have worked on it for several days and have not been able to get a good setting from retarded idle timing to 34 degrees max.

Thanks

 

[wired247]

Re: 1974 Mercury 500: Thunderbolt ignition replaced with magneto

Yank that crap and install the right ignition. Stop trying to fix someone elses jury rig.

 

[merc850]

Re: 1974 Mercury 500: Thunderbolt ignition replaced with magneto

If that motor has Perma-Gap plugs I doubt it will ever run properly without Thunderbolt ignition, this site sells trigger assemblies for Tbolt.