Make sure your boat is ready to go back in the water with Practical Boat Owner's comprehensive guide

Maintenance on a boat: 71-point skipper’s checklist

Maintenance on a boat: Underwater


A reduced shaft anode which really needs replacing

A reduced shaft anode which really needs replacing

These might be expensive, but don’t skimp on them – your underwater metals, from P-brackets to rudder bearings and seacocks, will thank you.

As a general rule, you should replace any anode once it has reduced by about 50% in size.

  • Check the bonding wires to ensure a circuit is made.
  • Don’t forget the anode attached to the engine block – it might be out of view, but it’s extremely important.
  • Apply Loctite to the threads of your shaft anodes to stop them loosening. Silicone sealant applied to the recesses over the nut and bolt heads also helps.
  • Teardrop-shaped anodes bolted through the hull should be checked for any movement or leaks. Replace their bolts at the slightest hint of corrosion or wear. Remember, you may need to draw a bolt in order to examine it properly.

Through-hull fittings

It is best to check seacocks when the boat is out of the water

There has been much debate regarding the use of seacocks made from ordinary brass or a bronze alloy that is susceptible to corrosion, potentially putting your boat at risk of sinking because of a failed and fractured seacock.

The perfect time to check them is while you’re out of the water.

Check that the metal hasn’t gone pink, which would be a sign of dezincification, and that the metal is being eaten away (rub off corrosion with a wire brush, if necessary).

If in doubt, replace the seacocks with DZR brass, bronze or plastic alternatives.

Similarly, check the skin fitting and any bolts or threads for the same reason.

If you’re unsure, give the hose or seacock a sharp tug to check the fitting doesn’t shear.

  • If you removed any hoses over the winter, ensure these are now properly reattached.
  • Check you can turn a seacock with two fingers. If you can, it should be fine – if you need more force it may need lubricating.
  • Seacocks have a habit of seizing up over the time you’ve been out of the water, so apply a lubricant and work them regularly to keep them moving.
  • If you have Blakes seacocks, take them apart and service them.
  • Don’t forget the cockpit drain seacocks. Usually left open during the winter lay-up, they can seize in the open position.
  • Check the blanking plates are in your speed and depth transducers before the boat is lifted in.

Keel bolts

Check your keel bolts and studs. If you have any doubt about their integrity, seeks advice from a surveyor or experienced boat yard.

There are also other checks which can be done if the boat is ashore.

Full details at How to check keel bolts.

Maintenance on a boat: Down Below

Propulsion systems

Fuel filters om a boat

Fuel filters should be replaced annually

Before you relaunch the boat, de-winterise the engine – especially as this will keep antifreeze from entering the water when you run the engine afloat.

  • Check and replace the water pump impeller if it shows sign of ageing. Don’t forget to install a new gasket on the pump faceplate.
  • Remove any rags stuffed into inlets and exhausts.
  • Re-install or replace any engine belts you may have removed.
  • If the yard allows you, start the engine with the inlet hose in a bucket of water to check it’ll start when you’re afloat.
  • Check your fuel tank for condensation. If there’s any sign of diesel bug sludge, drain the tank, clean it and refill, including some water-eliminating fuel additive.
  • Replace all fuel filters yearly – both primary and secondary – and re-prime the fuel system.
  • If your stern gland was dripping too much last year, repack it now while you can. If you have a greaser, refill it.
  • Check the cutless bearing by moving the shaft from side to side to check for play. There should be wear lines on the rubber: if it’s worn down to those, remove and replace the bearing. You may need a puller to get it out; don’t forget there may be hidden grub screws.
  • Finally, check the engine inlet seacock is open before launch.

How to service a marine diesel engine in 12 simple steps


In brief, check the spark plug and run the motor in a suitable container of water to check it works.

You may find that the petrol has gone ‘stale’ over the winter and needs replacing – and the carburettor and jet may need cleaning out.


For years, boaters have struggled to refill 4.5kg Calor Gas butane bottles

Check the regulator on the gas bottle

A quick check of the gas system is a must to ensure you don’t have a potentially fatal problem in the year ahead.

  • Check that all pipes and hoses are in good condition and undamaged.
  • Check the replace-by date on flexible hoses. Rubber pipe should have a clear run, with no chafe or kinking points.
  • Check the condition of the regulator: many aren’t built for the marine environment and will need frequent replacement.
  • The burners on your cooker may need cleaning as they often rust up: remove these and clear all the holes of corrosion.
  • Check your gas alarm is working by placing an unlit gas lighter near one of the sensors.

Maintenance on a boat: The Rig

A sheave on the mast of a boat

Check the sheaves. Replace any worn parts

A quick rig check now should ensure you won’t have a problem out at sea later.

Mast electrics

  • If your mast is down, check the contacts on any light bulbs. If not, it’s probably best to wait until you’re afloat to climb the mast.
  • Check the lenses for your nav lights are not crazed.
  • Clean up the contacts on your VHF aerial, and be careful with the cable – it’s easy to kink and break it, especially as it ages.
  • Check any wind instruments are working, and clean the contacts if necessary.


Look for signs of wear around all rig fittings, like shrouds on the mast of a boat

Look for signs of wear around all rig fittings, like shrouds

  • Check all riveted fittings for movement. It’s best to nip this in the bud early, as a moving fitting will enlarge its fixing holes and cause a far bigger problem than there was to begin with.
  • Check the backing plates for the T-terminals in the mast, and get them replaced if there’s any sign of cracking or deformation.
  • Check T-terminals, spreader roots and mast heel for stress fractures or any other damage.
  • Check the standing rigging. The wire should enter the terminal straight – if there are any kinks or bends, loose strands or suspicious rust marks, get it checked out. Insurers frequently state a 10-year lifespan for standing rigging: while your boat’s rigging may be fine and undamaged, especially if you haven’t pushed the boat too hard, it’s best not to risk skipping a thorough check.
  • Check the bottlescrews are not deformed in any way or have any fractures or cracks.
  • Check all the sheaves in the mast are running freely and are undamaged. If necessary, drive the shaft pin out and check – they often wear on the inside of the sheave. If they won’t turn at all, first try a kettle of hot water – it’s more effective and less messy than WD-40. When they’re moving, use a dry silicone lubricant to keep them that way.
  • Check every clevis pin and toggle: if any are in the slightest bit worn or bent, consider replacing them.
  • Remove any old tape so you can see exactly what’s hidden underneath. Inspect and re-tape.
  • Remove any tape or ties used to temporarily secure running or standing rigging to the mast during the lay-up. You’ll thank yourself once the mast is back up and you don’t have to climb aloft to remove bits of tape.


  • Make sure all sheaves and reefing lines run free.
  • In particular, check the kicker attachment. This is subject to large forces, and can begin to move as it wears its fixing holes. If necessary, re-rivet it to the boom.
  • Check the gooseneck pin and attachments for bending or stress fractures, and replace any components if necessary.


  • Check for chafe, wayward stitching and tears. Do you have a sail repair kit on board?

Maintenance on a boat: Electrics

  • Check and clean the contacts on the batteries.
  • Check the voltage. You probably charged all batteries over the winter anyway: if not charge them properly now.
  • If you have lead-acid batteries, check the electrolyte levels, topping up with de-ionised water if necessary.
  • Protect the battery terminals with a smear of Vaseline.
  • Make sure you have a full complement of spare fuses and bulbs.


A deck navigation light on a boat

heck the lenses of deck navigation lights are not crazed

  • Check deck nav light bulbs and connections, and that lenses are not crazed.
  • Switch your instruments’ backlights on to dry out any condensation.

Deck gear

A woman performing maintenance on a boat by servicing the winches

Renewing the grease on the winches will keep them running smoothly all season. Credit: Theo Stocker

  • It’s worth stripping your winches to renew the grease.
  • Rinse and lubricate the traveller and genoa cars – it’s worthwhile making sure that anything that should move does move, and that anything that shouldn’t, doesn’t!


an inflated yellow lifejacket

Inflate your lifejacket and leave for 24 hours to check for any leaks


  • Service your lifejackets: Remove the cylinders and soluble pills, wash the jackets in fresh water, then inflate the lifejacket orally and leave for 24 hours to see if they deflate.
  • Check your liferaft. Does it need servicing?
  • First Aid Kit: Replace any out-of-date items. Remember items like cling film, for burns, and seasickness tablets.
  • Deck safety gear: Check the lashings on your guardwires– these could save your life. Replace them if they are at all faded or damaged. Check your jackstays. If UV-degraded (webbing) or frayed or kinked (wire or rope), repair or replace.
  • Fire extinguishers: These go out of date. Replacing them is often a surveyor’s first recommendation and an insurance necessity.
  • Flares: Check the expiry dates, and ensure you have enough of each type. Ensure a heatproof glove is in the flare box to help with firing them.


  • Update charts from Notice to Mariners.
  • If using electronic charts, check with the supplier for updates. You may need to connect to wifi or connect the chart chip to your computer at home for updates.
  • Install operating software updates for your chartplotter or instruments.

Maintenance on a boat: Afloat

A yacht with a white hull and a white sail

Once you’re afloat, make sure you check for leaks

You can almost relax once your boat hits the water… but check these first to ensure she stays afloat!

Check for leaks in:

  • stern gland – get ready to tighten it with a spanner if necessary
  • engine water pump
  • cockpit drains
  • skin fittings
  • seacocks
  • bilges

Before you start the engine:

  • If you have a ‘deep sea seal’-type stern gland, you’ll need to ‘burp’ it by pulling back the bellow until seawater flows in. This will expel any air and avoid the gland running dry.
  • Open the inlet seacock
  • If the engine hasn’t been started all winter, consider spinning it up with the decompressor lever engaged, or turn it over a few times with the starter handle, if you have one.
  • Turn off any automatic bilge pumps until you’re sure the boat is dry – they’ll hide any water ingress until the battery dies and you’re not on board.
  • Give the engine a good run, checking that the alternator is charging the batteries, the cooling water is doing its job and the engine isn’t overheating.
  • If you didn’t change the oil in the winter lay-up, do so soon to protect the engine.

Enjoyed reading Maintenance on a boat: 71-point skipper’s checklist?

A subscription to Practical Boat Owner magazine costs around 40% less than the cover price.

Print and digital editions are available through Magazines Direct – where you can also find the latest deals.

PBO is packed with information to help you get the most from boat ownership – whether sail or power.

        • Take your DIY skills to the next level with trusted advice on boat maintenance and repairs
        • Impartial in-depth gear reviews
        • Practical cruising tips for making the most of your time afloat

Follow us on Facebook, Instagram and Twitter