Lip Seal
Lip seals, like the Tides Marine shaft seal, are dripless seals. The seal is made by a composite plug that bears directly against the shaft, preventing water from getting past the shaft at the stern tube. The shaft turns inside the seal, and lubricating water is plumbed from the engine's raw-water discharge. There is no dripping. No periodic tightening is required. Lips seals come with a spare seal that slides onto the shaft ahead of the seal assembly so that a worn seal can be replaced without having to haul the boat. They are self-aligning to some extent, thanks to the flexible hose used to connect them to the stern tube. Lip seals require a pristine shaft surface and may require more distance between the gear coupler and stern tube (shaft log to you old salts) than other seal types. The water supply must be regularly checked to ensure safe and proper operation, but lip seals can last for years.