I've lost the drive on my Mariner 3.3 and my first reaction is to look at the dog clutch. It looks as if I need to separate the motor from the lower part at the joint just above the clutch but despite having removed 6 screws from the underside the two halves won't separate. Am I "missing a screw", do I need to remove the clutch control shaft, is it all just glued together by a gasket or should I be dismantling at some other point?