77 Merc 500 thunderbolt started/solenoid issue

[hotrod53]

When I try and start my Merc 500, I turn the key and nothing happens for about 3 seconds, then the starter begins to crank. It doesn't do it once ive started it a few times. First time out it took a really long time before it cranked. A few seasons ago I disassembled the starter checked the brushes, and lubed the armature bushings.

My battery is full charged, I can see this being a starter or a solenoid issue. Has anyone experienced this? I'm just trying to head off getting stranded.