IF THE BOAT IS OUT OF THE WATER, WITH THE ENGINE OFF, PUT IT IN GEAR. TURN THE PROP BY HAND. IT SHOULD ENGAGE IN ONE DIRECTION. IF IT DOES, YOU MORE THAN LIKELY SPUN THE COUPLER. YES YOU DO HAVE TO PULL THE ENGINE, BUT IT IS ONLY A COUPLE HOUR JOB. TO EXPEDITE THE JOB, TAKE THE OUT DRIVE OFF. THE REST IS FAIRLY EASY FOR ANY MECHANIC. THE COUPLER IS ATTACHED TO THE FLYWHEEL WITH THREE BOLTS. FROM START TO FINISH THE JOB SHOULD TAKE LESS THAN FOUR HOURS. DON'T FORGET TO GREASE THE NEW COUPLER.