Keeping your boat afloat with regular hull maintenance
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Fri May 31, 2024 at 4:30pm

Boats are in a constant battle with the elements and the water all around them, and therefore regular maintenance is the key to stop the water from winning!

Whatever your boat is made out of - steel, wood, or GRP there will be times when it will need to come out of the water for essential maintenance. Steel boats are usually removed from the water for 'blacking' every two to three years, and most marine insurance companies will demand a hull condition survey when a boat reaches a certain age, therefore, its essential to keep your boat's hull well maintained so you can enjoy many years of use.

Steel-hulled boats turn into a fizzing electrical "battery" when in water, which corrodes the steel and causes pitting from stray electrical currents in the water. This is why boats have anodes fitted, as these fizz away instead of the hull’s steel.

Essential engine maintenance tasks

The engine is the beating heart of your boat – make sure you keep a close eye on the following:

Fluid levels: Check the oil level in the engine and gearbox, your coolant level and your levels of battery fluid.

Drive belt: Ensure the drive belt has enough tension and monitor for visible signs of wear.

Moving parts: Ensure all moving parts of the engine are greased and bolts and connections are tight.

Fan belt: Look out for signs of visible damage or looseness.

Narrowboat maintenance checklist

It's recommended that you regularly carry out the following tasks for your canal boat:

Check your oil levels

Clean the boat's engine and check it's in good condition

Plug any leaks

Check the bilge pumps are working

Inspect the battery and top-up with de-ionised water

Look for any loose bolts or pipes

Inspect the cables and control equipment for signs of wear and tear


If your bilges are full of oil and water, this dangerous mixture could get into the engine with potentially disastrous consequences. It is important that you do not discharge the oil with the bilge pumps into the waterway, but manually dispose safely ashore.

Gearbox/Drive plates

If you hit an underwater object, the drive plate is usually the first victim.  As canal boats don't have a clutch arrangement, gear boxes tend to receive a fair bit of abuse, so go easy and regularly service them.


Always carry a spare alternator belt, and check its condition before setting off. Simply twist the belt and if there are cracks, or the edges are starting to look ragged it's time for a new belt. If you hear 'squealing' from an old belt, it probably needs replacing. If it's from a new belt, an adjustment is required.


If the bolts connecting the propeller shaft to the engine are loose, any movement will could sheer them off, which can result in loss of propulsion. Eventually the coupling will need replacing, and you may even have to change your prop shaft if the coupling has damaged it.

Narrowboat batteries

A standard narrowboat will have a minimum of two types of batteries: leisure batteries, which keep your heating and electrics running while you are cruising, and starting batteries, which provide the power to turn on your engine.

Narrowboat batteries follow the same principle as car batteries – they recharge as the engine is running. However, if left unused for too long, or if damaged, they can run flat. Your first warning sign of a battery with problems may be a flashing light on your dashboard - though this would not be in the case of older boats, which do not have dashboards. As soon as you become aware of problems with the batteries, immediately stop and investigate. You should also invest in a voltmeter from your local chandlery to check the state of the battery's charge. If your battery is running at less than 75% of its original capacity, you should aim to charge up as soon as possible.

Water holding tanks

Water holding tanks are normally found in the hull, although in some boats they will be kept in a separate container for easier access and removal. There is always a risk of leaks from tanks, especially as they get older, so you need to inspect them on a regular basis.

When it comes to drinking water, this can gradually acquire a ‘tank taste’ which, while not harmful, isn’t particularly pleasant either. The most effective option for cleaning your water tank system is to leave a solution of chlorine or hydrogen peroxide in the system for 24 hours, before flushing it out. However, please be careful if you do this, as if it is not done correctly you may cause harm.

Shorter term solutions include: Water purification tablets: If you’re filling up from an untreated source, these are essential and will make the water clean and safe to drink. Boiling: It’s simple and effective, although it can be energy intensive. Filters: Not especially effective, but it can keep out larger particles of dirt. Bottled water: Although it can be expensive, bottled water might be the easiest option.

Water and bilge pumps

Your narrowboat’s water and bilge pumps are typically situated within the engine space. The most basic pumps are hand-operated, but there are also different types of manual, electric and automatic electric pumps.

Check your narrowboat’s manual for advice on their usage. A bilge pump should always have a power connection so ensure it is wired to the main batteries in the craft. When you turn the power off to leave the boat unattended, you don't want to turn off the bilge pump. Therefore, connect an automatic bilge pump directly to the battery, not through the distribution panel.

Narrowboat water pump problems include, Broken accumulator tank - If the accumulator tank is full, the pumps can’t function properly; Water not flowing - You may have a worn or broken part in the pump.

Narrowboat heating systems

There are three common heating options in a narrowboat. These are sometimes found on their own, but can also work in conjunction with one another:

Diesel-fired central heating system - These work the same as the boiler in your home making them a popular option and require annual maintenance.

Gas systems - These run off bottled gas, which is normally stored in a locker on the boat. It’s cheap and efficient, but there’s a risk of portable bottles being stolen. Gas systems should be checked annually by a qualified gas engineer.

Multi-fuel stove - Capable of burning both wood and coal, these are appealing but can take up extra space – both for the heater itself, but also for the fuel.

Narrowboat windows

There’s a huge range of narrowboat window and porthole types available, although basic maintenance is common to all. To keep the heat in and prevent mould build-up, check liners and seals for signs of wear and tear, and replace if they begin to look shabby.

Narrowboat hull inspection

The hull of your narrowboat will take the brute force of the elements. This means it should undergo regular inspection to avoid leaks and other damage. It’s best to keep an eye on rust, corrosion and pitting, and don’t forget to have the inside of the hull checked over too.

Since the hull is normally out of view, you will need to organise regular inspections by a professional. You will be required to take the boat out of the water in order for a marine surveyor to carry out a review of the state of the hull. As a rule of thumb, this should be done every three to four years – or more often if you’ve sustained any accidents.

A qualified marine surveyor can inspect cruising damage, hull build quality, outlets and penetrations, and plate thickness.

Hull blacking

Blacking the hull helps to maintain the condition of your narrowboat by minimising the risk of rust and corrosion.

Hull blacking involves extensively repainting the hull, and this should normally be done every two to three years. It is entirely possible for you to black your boat's hull yourself. However, you will, of course, need the means to take the boat out of the water, and the time to paint it – meaning most boaters get it done by professionals at a marina.

Blacking the hull will take up to three days and involves cleaning the hull of muck and grime then applying a couple of coats of hard-wearing paint, before drying and returning to water.

Preparing for the long haul

By taking the time to keep your narrowboat maintained, you will save yourself considerable money involved in repairs, replacements and call-outs. Keep our guide handy and follow the steps to ensure you stay cruising for years to come.