How to Replace a Shaft Seal (Remove, Measure, Install)

Replacing a shaft seal is a serious job because it sits on a below-waterline opening. If you are not confident, use a qualified marine engineer. Lasdrop’s own manuals recommend a skilled marine mechanic if you are unfamiliar with any part of the process.

This guide focuses on safe planning and correct principles, with key details pulled from installation guidance.

Por Callum Trickett
2 min de lectura

Replacing a shaft seal is a serious job because it sits on a below-waterline opening. If you are not confident, use a qualified marine engineer. Lasdrop’s own manuals recommend a skilled marine mechanic if you are unfamiliar with any part of the process.

This guide focuses on safe planning and correct principles, with key details pulled from installation guidance.

 

Safety-first planning (do not skip this)

  • Ideally plan the work ashore or in controlled conditions.

  • Have bungs and bilge pumping ready.

  • Read the manufacturer instructions fully before you loosen anything.

 

Step 1: Confirm alignment before removal

Before removing the old seal, slide it forward and verify the shaft is centered to the stern tube. Lasdrop explicitly calls this out because alignment affects seal life.

Step 2: Remove coupling and old seal

Once aligned, remove the shaft coupling and remove the existing seal or stuffing box assembly. (Exact steps vary by boat layout, so treat this as a scope marker, not a one-size-fits-all script.)

Step 3: Prepare the shaft correctly

Lasdrop guidance includes:

  • Clean the shaft thoroughly using very fine sandpaper (400 to 600 grit)

  • Remove sharp edges or burrs from the shaft and keyway

Step 4: Install the new seal assembly correctly (high level)

For lip seal style installations:

  • Lubricate with liquid soap

  • Slide the seal assembly carefully onto the shaft

  • Avoid damaging the primary seal during installation

For Gen2 installation steps, Lasdrop also highlights:

  • Use liquid soap to lubricate inner rod seals and shaft

  • Do not use oil, grease, or silicone as a lubricant

Step 5: Clamp, orient, and reassemble

Lasdrop installation guidance notes:

  • Clamp the assembly to the stern tube using supplied clamps

  • Position water injection ports facing up

Step 6: Water supply, do it properly

Lip seals and Gen2 require water for cooling and lubrication. For faster boats, water injection is mandatory, and Lasdrop recommends sourcing water from a clean point after the raw water pick-up and avoiding debris-prone sources.

Step 7: Double-check and sea trial

After installation:

  • Monitor for leaks

  • Monitor temperature at the seal

  • Verify water feed is flowing as intended

 

Shop Lasdrop shaft seals and replacement lip seals here!