Traditional stuffing boxes use packing compressed around the shaft. Some are designed to drip slightly while turning for lubrication and cooling. Dripless systems may use a mechanical face seal or lip seal and can require venting or water feed. Apply only the maker’s instructions.
A water-lubricated cutless bearing supports the shaft in a rubber-lined sleeve. With the vessel safely ashore, movement can be checked at the propeller, but allowable clearance depends on shaft diameter, bearing design and service criteria. Uneven wear may indicate misalignment, bent hardware or poor water flow.
Warning signs
- Increasing drip rate or spray
- Seal or stuffing box running hot
- Black rubber debris near the bearing
- Rhythmic vibration that changes with shaft speed
- Fretting or movement at coupling bolts
- Corrosion pitting in the seal track
- Shaft difficult to turn with gearbox in neutral, where the system permits that test
Alignment includes engine position, coupling faces, shaft straightness, bearing line and hull condition. A flexible coupling does not make gross misalignment acceptable. After grounding, rope entanglement or propeller impact, inspect the whole driveline.