Maintaining your boat

A well-maintained vessel is basic to safety at sea. Poor motor maintenance alone is responsible for thousands of calls for assistance each year.

This page covers maintenance techniques and schedules that skippers should be aware of to keep their vessels in a reliable and seaworthy condition.

  Routine maintenance 'BEST' boat check

To assist skippers and reduce the number of boating breakdowns DoT has developed the BEST boat check. The BEST check should be completed prior to every trip to ensure your Boat, Equipment, Safety equipment and Trailer are all in good order for a day on the water.

  • Boat.
  • Equipment.
  • Safety.
  • Trailer.

The BEST check ensures your day is not ruined by an oversight, it's a quick activity to give peace of mind.

A well serviced boat should not let you down. The annual 45 point check will help skippers identify issues before they become a problem, but it all starts with having a regular service. Take the time to have your boat serviced at least once a year.

The BEST and 45 point annual checks lists will not cover all types of boats and voyages but there's no doubt they can help make your next voyage less stressful and possibly much more enjoyable.

  What to check

Manufacturers usually recommend a service by a specialised workshop at least once a year, even if you use the motor very little.

This ensures that vital internal parts, like the water pump, get looked at.

If you work your motor hard, then you should have the gearbox oil changed every three months.

Spark plugs
Spark plugs

Electrical system corrosion

Electrical systems on vessels commonly fail through corrosion.

  • Keep all electrical systems clean and corrosion free by frequent inspections.
  • Spray terminals, electrical connectors, etc. with a corrosion-retarding agent. Keep all electrical fittings dry.
  • Check the navigation lights are working even if you expect to be out only during daylight hours.


One of the most common reasons for calling on marine rescue is a flat battery. Batteries deserve a lot of attention at regular intervals.

  • Use a genuine marine battery - your motor's handbook will tell you what capacity. Check it and charge it regularly. If the battery does not hold its charge, it should be tested or replaced.
  • Batteries should always be secured with brackets within a ventilated container.
  • If it is in an enclosed space, ensure it is properly ventilated.
  • Terminals and cables must be kept clean, and terminals greased.
  • Terminals and connections must be tight and secure.
  • Top up battery cells with distilled water and check each cell with a hydrometer if the battery is serviceable.
  • Turn off the power to the charger before disconnecting the charger leads. This may prevent an explosion.

Spark plugs

  • With modern engines, spark plugs generally last longer. If they fail, then cleaning them is not very likely to bring them back to life.
  • Carry a spare set of new plugs and a spark plug spanner.


Fuel is a key element in successful boating. Running out of it, disabling the engine because of dirt or excess moisture in it, or exposing it to fire risks are all possibilities against which you should take precautions.

Fire/explosion risks

  • Fuel, for engines or for stoves, is the most common component of vessel fires or explosions. Leaks in systems and ventilation shortcomings are the usual problems. Regularly inspect fuel and gas tanks, valves, pumps and lines for visual condition, especially corrosion, and leaks. Get problems fixed by an expert; temporary repairs can be dangerous.
  • Do the sniff test each time you board your vessel. If you smell fuel - find the problem.

Fuel system

  • Check and change filters frequently to be assured of clean fuel entering your engine. Carry spare filters.
  • Keep tanks topped-up and close them up when not in use. This reduces the chance of condensation occurring and putting water in your fuel.
Gear box oil
Gear box oil

Use clean, fresh fuel

  • Clean out portable fuel tanks at least yearly and replace old fuel after a long period of inactivity; water is likely to have built up in it.
  • If your motor uses pre-mix lubrication you should not use a petrol-oil mix older than three months. The oil will lose lubrication properties and produce sludge. For direct oil injection motors, ensure the oil reservoirs are kept full.

Gear box oil

  • Bleed a little oil from the drain screw in the gear case.
  • If water appears, or if the oil looks milky, take the motor to a service centre.


  • The rubber bushing of an outboard or stern drive's propeller can fail, especially if it has hit sand or rocks.
  • Carry a spare propeller, perhaps a second-hand one.
  • Keep props clean and in good working order. This includes removing the propeller, hammering out any small bends, and filing any jagged bits smooth or replace if badly damaged.
  • Snagged fishing line wrapping around the outboard leg propeller shaft can destroy the gearbox seals and allow water in.
  • Water in the gearbox will eventually cause it to fail. Remove the propeller regularly to check for fishing line, or any time you think you might have hit a line.
Image of a water pump
Image of a water pump

Water pump

  • Outboard water pump impellers are normally changed at the annual service. If you have been operating in the shallows and stirring sand, consider changing more often.
  • Make sure water is being discharged from the exhaust system or tell-tale when started.
  • Regularly check for water leaks.

Image of boat engine

Page last updated: Mon Feb 3 2020 2:39:31 PM