Tips for Winter Yacht Storage


Although we have left our boats in many parts of the world, this is the first time where we have had to consider sub-freezing temperatures. We talked to folks from various areas who live in these climates and received all sorts of advice, some of which was in conflict.

Our concerns were the following:

  • Avoid damage to the plumbing system and machinery from a prolonged freeze.
  • Keep the humidity under control so there is no risk of mildew or mold growing.
  • Maintain battery state of charge.
  • Keep an eye on the freezers, which have a few items left over from last year.
  • General security for the boat.

Berthon’s Boat Yard in Lymington, on the Solent in the UK is where we are hauled. They were recommended by several cruising friends and we have not been sorry we chose them. They assigned a project manager, Ian Stables, and as things come up, he is our point of contact.

To winterize the plumbing system we bought food-grade polypropylene glycol in bulk, mixed it four to one in a drum to give us antifreeze protection to zero F (-17C),and then pumped it into our domestic plumbing system. We also ran this through the bilge pumps, watermaker, engines, and genset, as well as the air conditioning and toilet systems.

In addition we rented three small heaters from Berthon’s, which are placed in the ends of the boat and salon. These have thermostats set to 40F (4C) and seem to be just enough to keep us above freezing during cold snaps.

We carry a home-style dehumidifier, which runs on 115VAC and 60 cycles. We were concerned with using it over the winter on 50 cycle power in the UK so picked up a local unit. This sits on the galley counter, empties through the sink, and shows a small wet stain on the topside indicating it is working. The dehumidifier is set to average 45% humidity (mold and mildew cannot grow below 55%).

Batteries are maintained by our Victron inverter/chargers. These hold a temperature compensated float voltage, and periodically kick up to a normal charge rate to keep the batteries fresh. Temperature compensation is particularly important with gel cell type batteries.

Berthon’s have hundreds of boats in storage and have a “valet” service to look after the boats. The regimen followed depends on Owner requirements. In our case, Simon Quinn, the valet manager, checks that the power connection is functioning, and once a week looks at our humidity meter, freezer temperatures, and verifies battery voltage. We would not be comfortable leaving the boat if we did not have someone trustworthy checking on her.

We’ll be back aboard towards the end of March and will report on how things have gone.

Posted by Steve Dashew  (January 30, 2009)

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