What to carry as spares on board: a season's consumables list

Spares on board are assembled by one rule: carry what fails predictably and stops the boat, and what's hard to find in an unfamiliar port. Everything else can be bought locally.

The list below isn't a "just in case" list — it's ranked by failure frequency. It fits in a single locker under a berth.

Engine and cooling

• Raw water pump impeller and cover gasket. The most common engine failure, lasts two to three seasons. A detailed breakdown — in a separate article.
• Alternator belt. Fails without warning, and along with the charging it usually takes out the freshwater pump drive too.
• Fuel filters, both: the coarse pre-filter with a water separator bowl, and the fine filter. Sediment stirred up from the tank in a seaway clogs a filter within an hour.
• Oil filter and oil for one change.
• Heat exchanger impeller or a cover gasket set — you'll end up opening the heat exchanger exactly when the impeller falls apart.
• Thermostat. A small part, but without it the engine either won't warm up or runs hot.

Fuel

• Manual priming pump or bulb, in case the factory one can't clear an airlock on its own.
• A set of seals for the fuel line. Fittings and durite washers.
• A couple of meters of fuel hose of the right diameter.

Separately: carry a funnel with a mesh strainer and water separator. Fueling from a drum in a small port is routine in the Mediterranean, and water in the tank costs more than any spare part.

Through-hulls and bilge

• Wooden tapered plugs, one for each through-hull, tied off next to the seacocks. A cheap item that can save the boat.
• A spare bilge pump, or at least an impeller and diaphragm for the manual one.
• Hose clamps, two size ranges. Stainless steel only, with a smooth (non-perforated) band.
• A meter or two of hose in common diameters.

Electrical

• Fuses of every rating used on the panel.
• Terminals and crimp connectors, self-fusing tape.
• A multimeter. Not a consumable, but without it troubleshooting turns into guesswork.
• A spare temperature or oil pressure sender, if the ones on your engine tend to give false readings.

Deck and rigging

• Winch service kit: pawls, springs, grease. A pawl spring is a two-gram part that can stop a winch from holding load.
• Sheets and halyards — at least one spare of a suitable length.
• Shackles, carabiners, retaining washers in common sizes.
• Webbing and cotter pins for the steering gear, if it's cable-driven.

Sanitation

• Head rebuild kit: diaphragms, valves, seals. A head failure won't stop the boat, but it will ruin a passage worse than most other breakdowns.
• O-rings and gaskets for the water circuit.

Tools, without which the spares are useless

An impeller puller, a set of wrenches and sockets, hex keys, a torque wrench, a headlamp, an inspection mirror on a handle, and gloves. Half the work in the engine bay is done blind, one-handed — a mirror and a headlamp save hours.

What not to carry

• Large assemblies "just in case" — starter motor, alternator, gearbox. They're expensive, heavy, and rarely fail. It's easier to have one brought to port when actually needed.
• Consumables with an expiry date. Rubber ages on the shelf too: an impeller that's sat for five years in the heat falls apart just like one that's been run to failure.
• Generic "marine spares kit" sets from the store. Half the items don't fit your boat, and the one you actually need is missing.

How to build a list for your specific boat

1. Walk through the boat and photograph the nameplates: engine, gearbox, pumps, winches, head, battery charger. How to do this — in a separate article.
2. List the consumables for each system from the manual.
3. Mark which of these stop the boat if they fail. That's your locker.
4. Once a season, check the rubber parts in your spares: they age.

If a rebuild kit for some item is no longer made, that's not a dead end — it's a routine sourcing task. Send a photo of the nameplate, and we'll figure it out.