Look in your vessel’s engine compartment and you will see a network of boat hoses of different styles and colours, writes Dag Pike.

It will be much the same if you lift the boards giving access to your bilges.

Boats depend on hoses not only to keep them working but also to keep them afloat, and these hoses can represent one of the most vulnerable parts of the boat.

Every hose in the boat should be part of your annual inspection and you also need to think about replacing them at least every 10 years.

When boats sink at their moorings it will usually be a hose failure that is to blame and think yourself lucky it happened at the mooring.

Cracking on a flexible hose is a sure sign of trouble

Out in the ocean a hose failure can be catastrophic and few owners seem to recognise that many hoses on their boats are open to the seawater outside.

Planning a regular replacement of the hoses is the best solution for reliability but how do you check your hoses on that annual refit?

One of the best ways is to squeeze them.

If they feel mushy, crumbly, or excessively hard, they need replacing.

Then look at the connection points and if the hose is swelling out around the securing clips, it has probably reached the end of its useful life.

Don’t be seduced into thinking it will last another year. If you want peace of mind, replace the boat hose.

Remove the hose from the skin fitting to check the condition of the hose tail. This one failed catastrophically. Credit: Ben Sutcliffe-Davies

Hoses are used to transport liquids around the boat and because of the many different types of liquid used, it is important to get the right type of hose for the job at hand.

There is no such thing as a multi-purpose hose and you need special hoses for applications such as the engine exhaust, the engine water inlets, the hot and cold domestic water supplies, the sanitation pipes, fuel, bilge pumps and hydraulics if you have them.

The list goes on and a full hose replacement can be a challenging job and quite expensive because some of these specialist boat hoses do not come cheap.

A full hose replacement is best left to a boatyard but there is no reason why you can’t replace one or two if they look a bit rough.

Boat hoses: Engine

One of the most critical hoses in the boat is the one that brings in the raw seawater that is used to cool the engine.

This has to be flexible because the engine is flexibly mounted.

A failure in this pipe would only cause the engine to overheat and the engine compartment to flood but the seawater is also injected into the exhaust system to cool the hot gases there.

Without that cooling water, the exhaust hose could catch fire.

This engine compartment is well fitted out with reinforced and fire resistant water and fuel hoses. Credit: Graham Snook

This cooling water pipe needs to be reinforced with either a stainless steel or semi-rigid plastic coil, and it needs to be a heavy-duty hose that you cannot compress with your hand so that it can withstand the suction of the seawater pump on the engine.

It can be tough to cut if it has a metal coil, and needs to be secured with double wormdrive clips.

Ideally it should also be a fire-proof hose.

Most of the other hoses on the engine come from the engine manufacturer and should only be replaced with proper engine spare parts but when we come to the other end of the engine there is the flexible exhaust pipe.

Check for wear and signs of fatigue in the exhaust hose near the elbow and other points of stress

This pipe comes under considerable pressure and there should be no compromises here.

The pipe should be reinforced with wire and it should be capable of withstanding temperatures of up to 250°C, although there are more expensive silicone-based hoses capable of withstanding even higher temperatures.

Boat hoses: Fuel

Also in the engine compartment, you will find fuel hoses.

Many of the fuel lines will be made of metal piping but you will still need flexible sections to allow for any movement of the engine.

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Any flexible sections should be made from approved material suitable for the fuel you are using, with petrol and diesel fuel lines requiring very high standards because of the nature of the fuel; they should also be able to resist fire for a limited period, allowing you time to get off the boat if there is a fire on board.

Gas hoses

High standards are also required for any flexible sections if you have a gas supply for the cooker.

It is usually orange in colour, marked with BS3212/12 or EN 16436-1:2014.

The hose will begin to deteriorate as soon as gas is passed through it, or anywhere that it is exposed to UV from sunlight. Also in the engine compartment, you will find bilge pump piping from the pump to an overboard outlet.

Gas hoses are amongst the most safety critical on any boat and need regular replacement. Credit: Graham Snook/Yachting Monthly

The piping for the bilge pump should have a smooth interior bore so that the water can flow easily and the routing of the piping, like most of the piping on board, should not have any sharp bends that might restrict the flow through the pipe.

Also, avoid any loops in the piping which again can restrict the flow.

You will usually find that the bilge pump piping is reinforced either with metal or plastic spirals so that it maintains its shape and does not kink.

Domestic water hoses

For the domestic hot and cold water supplies, boat builders often employ the semi-rigid piping used for some applications at home, which works well provided that it is secured in place.

There are different materials for the hot and cold water pipes, so ensure you get the right one for the job and if the piping carries drinking water then it needs to be approved for this.

If your tank water tastes stale, make sure you have a food-grade hose for your freshwater. Credit: Graham Snook

The temptation here might be to use the cheap, clear plastic piping but that tends to get brittle over time and it won’t work for the hot water side.

Vinyl is often the material of choice for water hose.

Sanitation hoses

Like the bilge pump piping, you don’t want to use piping with internal corrugations for the sanitary piping because here of all places you want a smooth flow of the waste.

If your heads smell, get blocked or are stiff, it might be time to replace the sanitation hose. Credit: Graham Snook/Yachting Monthly

The flow needs to be carefully planned because you don’t want any waste left in the pipe which can allow smells to permeate through the plastic.

Hydraulics

Hydraulic piping will need to be of the type that’s designed to cope with very high pressures.

Hydraulic systems need high pressure hoses with proper metal end fittings, but watch for corrosion. Credit: Graham Snook/Yachting Monthly

These are almost all the standard type used both ashore and afloat, with metal fittings at the ends that are only plated metal and liable to corrode, so a smear of grease might help to prolong their life.

Fitting of boat hoses

Finally, any piping – whatever it is used for – that is connected to a skin-fitting should be reinforced because if there is any failure of the pipe, the boat will sink.

It should not be possible to squeeze hose that is suitable for this job, unlike the type of radiator hose that you can find in cars.

This semi-rigid hose can be tough to fit onto the skin-fitting and it may be possible to soften the pipe a bit by immersing it in hot water before sliding it over the hose tail.

The engine intake hose must be flexible and reinforced and should ideally also be fire resistant. Credit: Bob Aylott

Make sure to get the right size of hose for the fitting and don’t be tempted to try and use a hose that is slightly larger because it will slide over the spigot more easily.

Dag Pike was one of the UK’s best-known nautical journalists and authors, covering both sailing and motor boating for many years.

Boat hoses are measured by their inside diameter and when looking for new hose make sure it has a suitable quality marking on it.

Don’t skimp or compromise on the quality of a replacement hose – your life may depend on it. It is also crucial to consider what the hoses are attached to and how they are attached.

I have covered the importance of jubilee-type hose clamps in another article (YM, Mar 21), but if the clamps are corroded or rusted, or are pinching the pipe in any way, they should be replaced.

There should also be two hose clamps on any pipes connected to an external skin-fitting because a failure could cause the boat to sink.

Similarly with the skin-fittings, it is worth removing the hoses from time to time to inspect the state of the hose tails underneath, as well as the overall state of the skin-fitting.

Signs of boat hose trouble

• Hose past printed expiry date
• Signs of weeping or porous material
• Cracking or perishing
• Crushed, kinked or constricted
• Calcified with restricted internal diameter