Benjamin Marauder pistol extremely hard to cock

The hammer might be binding in the tube. I had the same issue with a crosman 1701P. Here's a video I found that discusses the issue:
I have two 1720t's and a 1701P. Polishing the tube made all 3 much easier to cock and smoother. Good luck.
Travis dropped so much airgun knowledge, hope him and his family is doing well these days..
 
Checked the engagement stud and it was tight, took it out and retightened just to be sure. Tried tapering the slot ends as per video, that helped a bit but still harder to cock than it should be, certainly NOT smooth.

Would installing a stronger hammer spring make much difference in cocking, I have put in a stronger spring ??
Yes it would