Fin stabiliser seals and bearings during yacht haul-out

Fin stabiliser work at haul-out should start with inspection and measurement, not an automatic instruction to replace every seal and bearing. The lift provides access to fin surfaces, anodes and shaft movement that cannot be examined fully while the yacht is afloat.

This guide covers the out-of-water checks, Sleipner's model-specific shaft limits, the findings that may justify fin removal, hydraulic actuator checks and the records crew should keep. For operating principles and routine care between lifts, see our guide to zero-speed stabilisers.

Inspect the complete fin at every haul-out

Use every haul-out to inspect the stabiliser fins and components that cannot be checked properly afloat. The inspection should cover the entire fin surface and the fin anodes where fitted.

Record each fin separately with clear photographs. Include the overall surface, any damaged areas and the condition of each anode. These images create a useful reference for the work list and the yacht's maintenance records.

Sleipner specifies professional vinylester or epoxy repair for damage to the fin surface. Surface damage should therefore be assessed and added to the haul-out scope rather than left as an undocumented observation.

An annual diver inspection is recommended where possible, but it does not replace the detailed out-of-water examination. Log the diver's findings so they can be compared with the condition found at the next lift.

Measure radial and axial shaft play

Movement at the fin must be measured rather than judged by pulling the fin by hand. Sleipner recommends a dial indicator for this procedure, while the fact sheet also permits a micrometer. A trained technician should take separate radial and axial readings and compare them with the exact hull-unit limit.

For Sleipner SPS 65/66/67 hull units, the stated maximum is 0.10 mm radial play and 0.20 mm axial play. For SPS 55/90/91/92/93/94/96/97 units, the maximum is 0.15 mm radial and 0.30 mm axial.

Do not transfer either set of figures to a different hull unit. Record the model, measuring method and both readings so that the decision is tied to the correct equipment rather than a general impression of looseness.

Decide the seal and bearing scope from evidence

There is no defensible universal replacement interval for the main-shaft bearings. Sleipner says their anticipated service life cannot be predicted accurately because operation, loads and fin sizes vary. The decision must therefore use measured clearance, observed condition and the schedule for the exact model.

The same discipline applies when planning seal work. Use the model-specific manual and the physical findings from the haul-out rather than applying a calendar interval taken from another installation.

Fin removal should form part of an engineer's repair scope when the measurements or inspection identify seal, bearing or related hull-unit work. The available facts do not support removing every fin at every haul-out. They support a detailed surface inspection, instrumented play measurement and escalation where the applicable limit is exceeded or discernible bearing play is present.

After a new hydraulic fin installation or a major parts change, Sleipner calls for the first basic inspection after 100 operating hours or the first week of proper use. That inspection includes fin play, so it should be documented in the same way as the haul-out measurement.

Check actuators, hoses, oil and filters

The stabiliser inspection should extend inboard to the hydraulic equipment. Following a new installation or major parts change, the first basic inspection covers hydraulic-fitting tightness, hose chafe, cylinder rods, gland seals and the return-filter indicator.

Check the cylinder rods and gland seals for damage, leakage or scratches. Chafed hoses, a leaking gland seal or a scratched rod require an engineer's assessment rather than continued observation without a repair plan. Blueward Marine's yacht hydraulics service covers hydraulic fault finding and repair alongside stabiliser work.

Oil colour and filter indicators provide further evidence:

• White or grey oil: On the specified Sleipner system, this indicates water ingress or heavy condensation. The manual calls for replacement of the hydraulic oil and filters, followed by flushing.
• Restriction indicators: Check the pressure and return indicators six-monthly, with the oil above 40°C and the highest-flow consumer active. An indicator in the red area means the element must be replaced.
• Initial filter change: Replace the pressure and return filter elements after commissioning, no later than 50 operating hours.
• Subsequent filter changes: Sleipner's schedule sets every 2,000 operating hours or two years after the initial replacement.
• Hydraulic oil: For this system, the replacement interval is every 4,000 operating hours or three years.
• Heavy-duty or commercial operation: Sleipner calls for annual hydraulic-oil analysis.

Only carry out the indicator check under the stated operating conditions when it is safe and permitted under the yacht's procedures. Otherwise, leave the operational test to the technician and record why it remains outstanding.

Build a clear haul-out record

A stabiliser report should connect each observation to a location, measurement or photograph. Separate port and starboard findings, identify the exact hull-unit model and record radial and axial play individually.

The report should also include fin-surface and anode photographs, hydraulic-oil colour, filter-indicator condition, and any visible hose, rod or gland-seal issue. Where work follows a new installation or major parts change, record the first basic inspection against the manufacturer's 100 operating hours or first week requirement.

This evidence gives the captain and engineer a defensible basis for deciding whether the scope remains inspection only or expands to fin, bearing, seal or actuator work. It also prevents a model-specific clearance figure from being applied to the wrong hull unit.

What crew can check safely

Crew can collect useful evidence without trying to diagnose internal bearing or seal condition by feel.

• Photograph each fin: Record the complete surface and anodes where fitted. Arrange professional assessment of any surface damage.
• Arrange proper play measurement: Confirm the exact Sleipner hull-unit model and have a trained technician use the prescribed instrument. Keep both radial and axial readings.
• Inspect oil and indicators: At the six-month check, examine hydraulic-oil colour and the restriction indicators under the specified operating conditions. Report white or grey oil and any red indicator.
• Use diver reports between lifts: Where safe and permitted, arrange the annual diver inspection and retain its photographs and findings. Treat it as an interim check, not a substitute for haul-out inspection.

When to call an engineer

Arrange technical assessment when the inspection moves beyond basic recording or identifies a condition requiring repair.

• Measured shaft clearance exceeds the limit for the exact hull-unit model, or there is discernible fin or bearing play.
• A fin surface is damaged and needs professional vinylester or epoxy repair.
• A cylinder rod or gland seal is leaking, scratched or otherwise damaged.
• Hydraulic hoses show chafe.
• Hydraulic oil is white or grey.
• Oil analysis identifies elevated brass particles, which the manufacturer warns can contaminate the system.
• A pressure or return-filter indicator enters the red range.
• The haul-out inspection identifies seal, bearing, actuator or fin-removal work.

Blueward Marine in Palma provides yacht stabiliser service, including related hydraulic work. Book a technical inspection and upload photographs, or call the 24/7 emergency line on +34 971 251 374 for an urgent fault in Mallorca.