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Once the rotor was resecured, the DSS worked fine. Even after I removed the four setscrews, which were on tight, I had to use a hammer to move the rotor back to its proper position. I found that the rotor on the starboard shaft was about 2 inches forward of the bellows and flange. One assistance call I responded to involved a 46-foot powerboat whose owner couldn't find the source of the water that was flooding his boat all he knew was that his pumps weren't keeping up. So, when the bellows finally returns to its natural, relaxed position, a tiny space is left between the flange and rotor. I made this mistake on my own vessel, a 40-foot Marine Trader Sedan, and when I removed the setscrews for the second time, the inner screws were surprisingly loose.Īnother issue with a spinning rotor is that the flange and rotor are so well mated that there is a suction effect between them, and the rotor can actually stretch the bellows beyond its relaxed position before the seal is broken. That alone is likely the cause of many of the problems I've encountered, as most owners and yard workers assume they should reuse the setscrews after work that requires the seal to be removed. According to one manufacturer's instructions, the setscrews are never to be reused, and a new set of screws should be used each time the rotor is installed. This happens more often than one might think. Once the bellows is relaxed, the mechanical seal between the rotor and flange is lost, and sea water can flow into the bilge. If the screws lose their grip, the bellows can slowly push the rotor forward on the prop shaft. Some DSS products use setscrews to hold the rotor in place. PROBLEMS RELATED TO THE MOVEMENT OF THE ROTOR