I had all 4 manifolds, risers and both starters replaced on my Merc 496 Mag HOs a year ago. The one engine was pulled out to get access in my tight 8'6" beam bilge. Now the port starter spins but is not turning over the engine. Can you get access in my extremely tight bilge
the port starter without pulling an engine?

Yeah, remove the exhaust manifold. Its a little tough but not impossible by any means.

Removing the starter is easy, removing the wires on the solenoid is hard.

Thanks for the info.