He first suspected the engine but eventually determined that the sound/vibration was associated with shaft rotation. Prior to haul out, his boat functioned normally but after being returned to the water the owner experienced, after some delay, considerable noise and vibration while underway. I recently received a report from the owner of a Helmsman Trawlers 38 who had hauled his boat out for some routine boatyard work. Explanation of the PSS shaft seal's components and operation. This water flow is not essential to the operation of the PSS at speeds less than 12 knots, but it does provide the benefit of displacing any air in the stern tube with water, which is essential to lubricate and cool the cutless bearing.įigure 1. A small water line originating from the engine raw water pump (on some boats it originates from the engine cooling water exhaust elbow) provides water flow and cooling to the shaft seal and the cutless bearings within the stern tube. The PSS maintains a watertight seal by means of a graphite flange that is firmly pressed against a rotating stainless-steel collar (attached to the shaft) by a spring-loaded bellows affixed to the end of the stern tube. This article is relevant to both varieties of seals – though specifically pertains to the PSS. The 31 uses a similar product manufactured by Eliche Radice. The Helmsman Trawlers 37, 38/38E, and 43 use the Packless Sealing System (PSS) Shaft Seal manufactured by PYI. These shaft seals usually offer reliable performance with relatively little maintenance however, some best operating practices can maximize your time cruising and minimize your time in the yard. Helmsman Trawlers® are equipped with dripless shaft seals to keep water from entering the bilge where the shaft exits the hull through the stern tube / shaft log.