Hi Jeremy, welcome to Outdoorking.
Our reel mower guru, Deejay (a died-in-the-wool Scott Bonnar 45 freak) is currently away from home for a family birthday, so he may not answer immediately but can certainly sort this out when he gets a moment to reply. Essentially, if the engine side clutch-half can slide along the crankshaft, the cutter clutch will not disengage, and that sounds like your problem. However SB/Rover used two different methods for holding that clutch half, a captive cotter pin on the earlier units and a pair of grub screws on the last ones made. There can be problems over time, especially with the cotter pin type, so Deejay will want to see pictures of the mower, the clutch, and the crankshaft where it goes into the engine-side of the clutch. If you post these right away, he will be able to help you more quickly when he comes on line.
