starter problems?

I have a 88 bay liner Capri with the 3.0 OMC inboard. Ever since I got the boat out this spring it has been difficult to start at times it just clicks. I can tap on the starter or cross out the solenoid and it will fire, once it is running everything is great. I want to remove the starter to clean the brush assemblies and or replace it if needed, my problem is I can not figure out how to loosen the mounting bolts the are wedged up against the structure. I have tried a socket, wrench and crows foot socket nothing seems to be able to grab the bolt. Any suggestions would be appreciated I may be just overlooking a simple way to do this I don't know.

I'd crack the bolts loose while the engine is warm. Warm bolts will be easier to loosen.
You can finish the job after things cool back down.

Use a six point wrench or socket ONLY.

Worst case scenario is you might have to pull the motor.