Twin Muir Windlass Overhaul & Seized Shaft Recovery, Classic Sailing Yacht

The captain of a classic sailing yacht alongside at Rivergate Marina in Brisbane booked us to remove both anchor windlasses for overhaul. She carries a pair of Muir windlasses on the foredeck, each driven through a horizontal gearbox under the deck by its own electric motor, and the vessel is more than thirty years old.

With the crew's bosun and engineers lending a hand, the deck-mounted components came off on the first morning and the port main shaft lifted out cleanly. The starboard shaft did not move, even under a 1.5-tonne jack. It was seized solid in its gearbox.

Day two brought a hydraulic power pack braced between the gearbox shaft and the top of the chain locker, and the shaft heated to around 200 degrees. Still nothing: the locker top was too soft to push against, and stripping the lower cover and bottom bearing only confirmed the main gear was locked to the shaft.

Rather than keep heating in a confined space or load the soft upper cover until it cracked, we put three options to the captain in writing and recommended the third: a controlled cut in the upper section of the chain locker, measured and cleared first, so the whole shaft and gear assembly could be lowered out through the locker access door and separated under control in the workshop.

The captain chose that option within minutes. The assembly came out whole, the cut section was reinstated and welded by the crew, and on the bench our hydraulic press did what heat and jacks could not.

Back in the Coomera workshop the condition report told two stories. The starboard gearbox was contaminated with sea water, its top cover corroded and two housing bolts snapped off, while the port box showed only ordinary wear with its seals intact.

Without an hour-meter reading or a service history for either, we recommended new seals and bearings in both, and the captain approved the electric motors going out for bench testing as a variation.

Parts came from every direction. New main shafts, bearings and seals arrived from the Muir factory in Tasmania, the gaskets and a plastic spacer washer were made locally rather than waiting weeks on a European import, and oil samples from both gearboxes went to the laboratory.

The motor test found the starboard unit's fan flange damaged and the repair quote close to the price of a new motor, so the crew sourced two replacements to the same IEC frame, which we checked against the original manual before they were ordered.

The starboard housing had its two broken bolts drawn out with slow, localised heat to avoid distorting the casting, every thread chased, and the corrosion sandblasted back to clean metal before primer and paint. The adaptor plates and top flanges got the same treatment, the scored gypsy openings in the deck plates were machined and polished, and the above-deck stainless was treated with rust-removal gel.

Cleaning the deck plates also answered a question the captain had raised: why the windlass had been rotating on its mount. The mounting bolts were bent, so they had lost their clamping torque, and a full set of new stainless bolts went on the order.

With the Muir parts landed, both gearboxes were assembled in the workshop, the new shafts test-fitted against the main gears for contact and tolerance, and each box prefilled with oil and left to stand so any seal weep showed before it went aboard.

Installation ran to a written weekly plan. Deck plates and below-deck adaptors went in first on fresh Sika, with the area tented against rain while the sealant cured, then the gearboxes were bolted up and torqued, the crew fitted and wired the new motors, and the gypsies, capstans and chain pipes went back on with the grease points cleaned and unblocked.

Both windlasses were run through their tests on deck, greased to the monthly schedule and handed back operational, with the chains laid ready for the anchors. A final set of PTFE washers had to be machined from bar stock, as nothing on the market matched the diameter, and went into the post with a spare under-gypsy washer kit for the crew to keep aboard.

Gallery

From the project

Starboard top gear flange as it came out, verdigris through the casting and the bore stained by sea water The same bore after mechanical cleaning, ready for its new bearing Adaptor plate rusted through its recess before treatment Adaptor plates and top flanges sandblasted, primed and painted, bores masked The windlass openings seen from inside the chain locker, corrosion around both New stainless mounting bolts and washers to replace the bent originals New main shafts from the Muir factory beside the old ones Worm shaft and new taper roller bearings laid out for assembly Gearbox cover with its new locally cut gasket and lip seal Both gearboxes on the bench in the Coomera workshop, assembly under way Both gearboxes bolted up under the foredeck and torqued, ready for their motors Deck plates fitted on fresh sealant, the remaining parts wrapped on deck One of the new electric motors coupled to its gearbox and wired by the crew Chain pipes and gypsies going back on the foredeck Capstan shaft greased before the capstan went on New lip seal fitted at the top of the chain pipe PTFE washers machined from bar stock, posted to the crew with a spare washer kit