I recently went through this on My
Catalina 42 with the same, VM 800,
windlass. My symptoms were EXACTLY like yours. I removed the
motor, two bolts, didn't have to do anything with the
gearbox. There is a 5 millimeter roll pin at the end of the
motor shaft where it goes into the
gearbox. On mine the pin broke and was slipping. If I pulled the anchor and chain up by hand the windlass would take up the slack, but slipped under load. I had to jury rig it but West
Marine ordered the pin, approximately $5.00, and it is as good as new. The pin is not in their catalog or on-line but WM staff can find it on their computer.