The fault lay hundreds of miles away where a mechanic improperly secured the shaft inside the coupling. But the blame for risking the boat and lives on board fell squarely on me. A week earlier, I noticed a 1/16-inch shiny band on that shaft at the back of the strut, but I failed to recognize that the shaft was already migrating aft. The lessons? Even when others do the job, understand the mechanical workings of your boat so you’ll know when something seems amiss, and then pay attention to those warnings.