I have a Tartan 30 that a PO converted to wheel steering. Today the chain that goes over the toothed sprocket came off the sprocket and was just sliding on the drum next to the sprocket teeth. Fortunately I had an emergency tiller so we were able to get home safely. The cable and chain did not break and the cable is properly on the quadrant. The cable and chain are too tight for me to lift the chain back on the sprocket and I'm too big to get down where the quadrant is to release the cable. What could have caused this? It hasn't happened in 4 years and the conditions were not tough (low speed, under power, lowering the main). Is there a quick way to correct this and how do I prevent this from happening again?