Electrical/starting problems

My ‘64’ Mercury with a 390 is giving alot of trouble. I had the starte checked, replaced the solenoid, relay and voltage regulator. My battery is good, ground is fine. No bare wires, alternator is fine, ignition switch is brand new, coil is good as well. HELP!
It was starting fine, I went out 45 min. later and it would only click, not turning over at all.

Sounds as if it is a bad stater. I would replace it. Sometimes you can wrap on the starter and it will work for a short while.

There are a lot of possibilities here including a worn out key cylinder, a blown fusable link (I’ve seen them become intermittent when blown), and a bad starter, specifically the bendix assembly portion. That subassembly 91) connects the starter motor’s gear to the flywheel ring gear and (2) closes contacts that enable the starter motor circuit. If knfenimore’s trick helps, than either the bendix assembly is sticking (rare-very rare) or the contact points are fried (common-very common). It’s also not unknown on an old motor for the commutator segments and/or brushes to wear out or the windings to develop internal shorts in a manner that disables the motor when it stops in a particular position (on a particular segment).

What I’d suggest is checking to see that you have 12VDC at the motor when the key is in START. If not, suspect the key cylinder, the starter relay, and the fusible link. If it is there, it’s the motor.