A buddy and I were heading out on his boat for a morning of fishing, at a low rpm, when I asked, “What’s that high-pitched sound?” I thought it was a belt, but when we went below and looked in the engine compartment, all seemed fine. The noise seemed to be coming from behind the engine. Our examination of the packless sealing system (PSS) unit revealed that the shaft, boot and clamps were hot to the touch.
My friend said everything was working fine when he used the boat the previous weekend. The only thing that had changed was his diver had changed the shaft zincs and cleaned the hull. I suggested that maybe some of his air bubbles had traveled up the groves in the cutless bearing into the stern tube. The rising air may have displaced the water, and air, instead of water, had filled the bellows hose and shaft collar of the shaft seal. With no water lubricating the rotating bearing, things predictably got hot. To resolve the problem, I gently pulled and compressed the rubber bellows boot, no tools required, to break the air seal. A gush of water came in and cooled down the parts.
If you have this system, remember this when you go back into the water after a haulout, or if a diver spends a time near the prop and shaft. If you have an older setup, as my friend did, always “burp” the bellows on the shaft seal to make sure it’s filled with water. Since about 2002, manufacturers have designed a hose nipple on the units that can either vent the air or inject water from the engine.
A few years later, my wife and I were on a month-long cruise through the San Juan and Gulf Islands, when at the end of the day I went into the engine room to conduct an inspection of the engine, pumps, sea strainers and batteries. To my surprise there were about five gallons of water in the bilge — not good for a normally dry bilge. A quick inspection revealed one of the dripless shafts was leaking. I assumed that some small debris had entered the unit and worked its way into the seal. Once again I burped the unit, which flushed the foreign object out, and all was fine for the balance of the trip.
Dripless shaft seals are standard equipment on most new vessels, and they are very reliable and require very little preventive maintenance.