The OP identified the servo in the original post, a Traxxas 2080 micro servo. I’ve not had good luck with Traxxas servos but some like them. The OP’s kit boat is a tiny, well-known proven model, no need to reinvent the wheel with different rudders, etc. The cause could be his use of a push/pull linkage, binding is common in those. The recommended linkage was a single push rod. KISS.
He should consider upgrading to a metal-geared servo, a mini if he has the room.
