I assume that you're backing into the slip ..... a boat with a right handed prop will move its stern to port when going astern ... if you give it enough of a 'short high burst' of rpm on the prop.
Especially if the boat has a rub rail ..... bring the boat to the slip on the port side and steer to have it at about a 45 degree angle. Burst a little reverse rpm and hop the stern over to the portside outermost piling, lay the boat onto the piling and stop it dead using either forward or reverse. then with the rudder hard over to starboard giving small bursts of engine rpm will steer the boat back into the slip .... using the outtermost portside piling as the 'pivot point' .... just 'slide' along the piling using either short 'bursts of rpm' to 'steer' (leave the rudder alone). Called 'backing and filling ... and cheating with a piling as a pivot point.
If you dont have a rubrail and have an awgrip job ............. .