Fuelling systems in boats don't need to be complicated. They work much like every other vehicle, but it's the minor details that most boating enthusiasts get wrong. In simple terms, starting the engine activates the fuel pump. This draws fuel from the tank and transports it through the fuel lines, and the fuel is then cleansed of contaminants and impurities in the filter before reaching the cylinders. Fuel can be injected directly or through separate injectors into the combustion chamber depending on the engine. Petrol engines will include spark plugs to ignite the fuel, while diesel variants rely on increased compression for the same task.

A breakdown of the components and how they work, should resolve any queries, and ensure that fuel is delivered as it should. This ensures that the engine runs smoothly at all loads.

Fuel Tanks

Fuel tanks come in two types - portable or permanent, and largely based on the size and type of the vessel. The first can be removed, comes in capacities between 4 and 200 litres and is usually made of crack and corrosion-resistant high-density polyethylene (HDPE). Permanent tanks are fixed in the hull, hold much more fuel, and are often made of aluminium or stainless steel. They're more common on larger powerboats. Both types need to be secured and have some form of venting to prevent spillage.

Fuel Lines

Lines are what connect tanks and the engine. They are made of puncture and chemical-resistant materials, either reinforced rubber or plastics, come in various lengths and diameters, and usually with the right fittings to ensure there are no leaks. When buying a fuel line marine ensure you get the right type. Fuel lines for outboard motors are often offered as a complete assembly, additionally including a primer bulb to get enough fuel in the carb or injection chamber, so the engine can start without issue, as well as quick-release fittings connecting the line to the tanks and engine on either end. There are also universal fuel lines or those that use spigot-type fittings or are non-included, considering most engine manufacturers require their own custom connections and fittings.

Fuel Line Accessories

Primer bulbs are fitted to most fuel lines for boats with carbureted engines but generally aren't found in those with EFI systems. As mentioned, fittings vary, though some may look very similar but not be right for your boat. Some manufacturers have the same fittings at either end, but some also use completely different fittings, and in different sizes and thread types to connect the fuel line to the tank or to the engine. Here you should also consider how lines are attached to the rest of the boat. To remove play and secure the line along its length, use even-spaced steel clamps.

Choosing the Right Fuel Line for Your Boat

The right fuel line marine is one that can deliver the right amount of fuel and at the right pressure, without succumbing to damage or causing leaks. Here, look to materials that are resistant to harsh marine environments, and those that won't degrade or corrode.

Also, get the hose that is compatible with the engine fuel type to ensure there is no damage to the engine or other fueling parts. A major mistake is getting lines in the wrong diameters, only finding that they won't fit. Diameters also determine that fuel is delivered at the recommended pressure. Most outboard engines usually gravitate toward lines that are 10mm in diameter, but other sizes are also available. Check with the engine manufacturer for recommended sizes. Lastly, make sure that the fuel line you're buying is compatible with Australian standards and regulations (there should be compliance markings on the outer material) to ensure optimal performance, fuel efficiency and safety.

Fuel Filters

Filters clean the fuel reaching the engine. Most boats have two, with one primary filter located near the fuel tank that removes water and larger particles and a secondary filter just before the engine. Most outboards have spin-on types that make for simple maintenance.

Fuel Pumps

Pumps are considered the heart of the fuelling system in your boat. They draw fuel from the tank, send it through the fuel line marine and filters and into the engine combustion chamber. Pumps also ensure that fuel is delivered at the right pressure for optimal performance. There are two types - mechanical which are activated by a rod or lever from the camshaft, or electric pumps found in newer vessels and more in tune with the higher pressures marine engines need.

Carbs and Injection Systems

Carburettors or more complex EFI systems with injectors mix fuel and air. Carbs are more common on older boats and engines and are simple to maintain, but not as efficient. Most engines today have modern injection systems that offer better fuel use, increased power and reliability, but will be more costly to service, both in terms of parts and labour.

Since boats don't get regular use like cars or motorbikes, fuelling issues are more common. Stale fuel, microbial deposits and water can all cause havoc. To keep the engine running smoothly and at its full potential, do thorough checks of all fuel system parts, and ensure you're using the right fuel mixture.