How to store boats over winter

Storage of boats over the cooler months can lead to problems afterwards; John Eichelsheim suggests ways to avoid or minimise the more commonly encountered issues.

Sadly the warmer weather is drawing to a close, and many boaties and anglers will soon pull their boats out of the water or tie them up for the last time until spring. It might be October or November before they’re used again.

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For the most part New Zealand’s climate is benign enough that we don’t have to go to the lengths necessary in some countries to prepare our boats for winter storage. But if you’re not going to use your boat regularly through the winter, it pays to follow some sort of ‘winterising’ regime, otherwise you may be frustrated by a boat that won’t start or lets you down in some other way when next you use it.

If you live in a part of the country where the stored boat might be exposed to frosts and freezing weather, winter protection is sensible.

Most boat-service centres offer packages to prepare boats for a winter layoff, and that’s a safe and convenient option, but boaties can save themselves a few dollars and do the work themselves.

How to store boats over winter

The engine

Most of the problems exhibited by boats after a lay-off are the direct result of lack of use. If you use a boat regularly, it’s far less likely to let you down, regardless of its age, but if you must lay up your boat for any length of time, following the guidelines below should ensure it’s ready to go next time you are.

The most common issues boaties experience the first time they use their boat after a winter furlough are caused by stale and/or water contaminated fuel.

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Petrol spoils quickly. Volatile elements gas off over time, reducing the octane rating, and the fuel further degrades through oxidisation. Modern fuels often contain ethanol. Ethanol can separate out if the fuel is exposed to water, which is more likely with a half-full tank. Pre-mixed fuel degrades especially fast, and the two-stroke oil can settle out over time, risking engine damage. In all cases, heavier elements settle on the bottom of the tank and may cause varnish and gum deposits in the fuel system and cylinder bores.

Symptoms of spoiled fuel include failure to start, loss of power/ poor throttle response and engine stoppages. Water in the fuel is caused by leaking fuel tanks or, more often, by condensation inside the tank. Keeping the fuel tank topped up can help to deter condensation, but a water separation filter is a worthwhile investment for any petrol-powered boat.

Some authorities recommend topping off the boat’s tank with fresh fuel so there’s less chance of condensation forming, but it may be safer to leave what’s in the tank and dispose of the old fuel before next using the boat. Otherwise, if you leave the petrol tank full, add a fuel stabiliser.

Flush the engine with fresh water using muffs or by connecting a hose to the flushing port. Start the motor and, with the cowl removed, spray fogging agent (fogging oil) into the air intakes on the front of the engine. While it’s still running, remove the fuel line and let the engine burn all the fuel in the line to prevent a build-up of deposits in the carburettor from evaporated petrol. Keep spraying fogging agent until the engine dies. This procedure is especially important for carburetted engines; you can dispense with the fogging agent for fuel-injected engines.

Remove the spark plugs and spray fogging agent into the holes to coat the cylinders’ interior surfaces. Then rotate the flywheel a few turns to spread the oil around. Check and re-gap or replace spark plugs as required before re-installing.

If required, replace the water pump impeller.

For an inboard engine with a closed cooling system, flush the engine with anti-freeze using an intake hose to the water pump. Place one end of the hose in a bucket or container of antifreeze and run the engine until anti-freeze exits at the exhaust. This is only necessary if the stored boat will be subjected to sub-zero temperatures; flushing out the old coolant and replacing it with clean fluid is sufficient in most cases.

Make sure all the water drains from an outboard motor’s cooling system by leaving the outboard upright until no more water comes out. Always store outboards upright to prevent water going where it shouldn’t.

How to store boats over winter


  1. Protecting your boat need not be expensive with covers available to fit most boat configurations and sizes available off-theshelf.
  2. If storing your boat outside, suitable security needs to be in place for your own peace of mind and that of your insurance company.
  3. Sacrificial anodes should be checked. Working correctly, they ensure the ravages of the marine environment, mixed with electrical current, are greatly minimised.
  4. At the end of the season, a bit of time spent with a grease gun can prevent issues come spring time.
  5. Keeping the fuel tank topped up can help keep condensation at bay, but a water separation filter is a worthwhile investment for any petrol -powered boat.
  6. A little preventative maintenance around wheel hubs and brakes before you store your boat will put you in good stead for the new season.


Tied up

Boats laid up on a mooring or a marina pose slightly different storage challenges. In New Zealand there is generally no need for full winterisation, but if a boat is likely to get little use for several months, there are measures you can take to mitigate the worst effects of prolonged disuse.

Most of the measures suggested for trailer boats are also applicable for outboard, stern-drive and petrol-inboard-powered launches. A haul-out may be necessary.

For powered vessels, it’s important to top off the tanks to minimise condensation. Add biocide to control diesel bug.

For engines with closed-circuit cooling, change the engine coolant. Also change the engine and transmission oil.

For engines cooled with raw water, flush the raw water circuit.

Use the fresh-water flush connector if you have one, otherwise close the intake seacock, disconnect the hose on the outlet side of the raw water pump and disconnect the cooling water discharge hose from the exhaust manifold or riser.

Run fresh water through the discharge hose to back-flush the water passages and rinse out salt. Either direct the discharge overboard by extending the disconnected pump hose or let it drain into the bilge where the bilge pump can take care of it.

Drain the muffler canister.

Grease all control cables, lubricate linkages and pivots, and spray unpainted parts with CRC or similar anti-corrosion aerosols.

Tighten the stuffing box to eliminate drips, but remember to loosen it again before using the boat.

If the boat is going to be idle for several months, it pays to seal all engine and tank openings to keep out moisture: air inlets, crankcase and transmission breathers, exhaust outlets and tank vents. Plastic bottle caps can be taped over openings to create an airtight seal. If you cover the fuel-tank vent, puncture the cap to avoid pressure build-up.

Wise boaters visit their boats at regular intervals to air boat interiors, check on batteries and bilges, and run the engines. Batteries should be kept charged, either with a passive solar system or some other charging system running off shore power. If shore power is available, run a dehumidifier as well. Lift squabs and mattresses so they can breathe and open up the boat whenever possible to circulate fresh air.

How to store boats over winter

Change fuel filters and water separators.

Remove the propeller and grease the propeller shaft and threads with a water-resistant marine grease. Check the rubber seals for fishing line or other damage. Do the same for a sterndrive, also checking the rubber boot for damage and removing any growth on the lower unit. Clean with soap and water.

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Change the gear case oil, checking the old oil for water ingress, metal fragments/shavings and any foreign bodies. Water in the oil makes it grey and cloudy, but so does air. Change the oil only after the engine has cooled and any air suspended in the oil has had time to find its way out again. Water in the oil means damaged seals, which must be replaced before next using the boat.

Change the engine oil. Do so while the engine is warm because it runs out more fully. On an inboard engine this is also a good time to change the transmission oil and oil filter. Grease all fittings and check fluid levels in hydraulic steering or lift pumps, as well as lubricating linkages and electric-starter-drive mechanism as specified in the owner’s manual.

Give the engine exterior a good clean and polish, or even a wax using a decent automotive or marine wax, and spray under the cowling with an anti-corrosion aerosol.

The boat

The best place to store a boat is out of the water, preferably indoors. At least ensure the boat is well covered to keep the weather out. There are plenty of good quality boat covers available.

Wash the hull thoroughly. You can use a water-blaster to clean off any barnacles or marine growth. Check the hull for damage, blisters or scratches, and repair as required. Why not give the boat a good wax (fibreglass and paint), paint touch-up, or a fresh coat of protectant (aluminium)?

Clean any through-hull fittings and strainers. Remove interior and exterior bungs and/or open any seacocks so the hull can drain.

Make sure batteries are fully charged and isolation switches are in the ‘off’ position. If the boat will be stored for a long time, consider hooking a smart charger to the batteries to keep them topped up. Solar-powered chargers can do the same job.

Where fitted, make sure the steering cable is packed with grease and remember to occasionally give the steering wheel a few turns during the course of the winter to prevent the cable binding – seized steering is a common boat-ramp disaster after the winter lay-off.

Pull up squabs and cushions and clean them using a mouldremoving solution on vinyl surfaces. Stow squabs propped up or on their sides so air can circulate around them.

Remove the miscellaneous gear that accumulates in any boat and store it somewhere dry.

If mains power is available, consider running a dehumidifier in the cabin at regular intervals to keep condensation and damp at bay.

The trailer

If the boat sits on a trailer, ensure the tyres are at the correct pressure and that the wheel bearings are well greased. If the boat is outside, tilt the trailer so the boat is slightly bow-up to drain any water that finds its way into the boat.

It pays to move the trailer every once in a while to keep everything moving, or jack it up and store it on blocks to preserve the tyres. Give the wheels a spin every few days. 

May - 2016 - Grant Dixon

New Zealand Fishing News Magazine.
Copyright: NZ Fishing Media Ltd.
Re-publishing elsewhere is prohibited

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