The useful life of flexible hose depends on many factors, including storage and operating conditions, and the hose may need to be changed several times during the lifetime of your boat. Flexible hose also has a lower fire resistance than metallic pipe and for all these reasons it is recommended that the length of hose used in the fuel system is restricted to the absolute minimum, i.e. the minimum length necessary to cope with vibration or the movement of engines and boat structures.
The additional benefit of this is that the amount of hose exposed to the risk of early failure through damage from heat and abrasion will be minimised. All hose used in the fuel system must be fire resistant to at least 21/2 minutes, as specified in the internationally agreed marine fuel hose Standard (BS EN ISO 7840), although there are hoses available with superior fire resisting qualities (e.g. BS ISO 15540). Both of these hoses will also meet the current requirement for reinforcement and wall thickness.
Injector leak-off (spill rail) arrangements must meet all the requirements for fuel feed and return pipes, hose and connections, or
- utilise the direct return to tank option, or
- return to the fuel system through a non-return valve.
- injector leak-off hoses fitted by the manufacturer within an enclosure on the engine meet the requirement.
Vintage and traditional engines designed to return the injector leak-off fuel to a catch pot are acceptable provided the catch pot is securely mounted and is free of signs of leaks, signs of damage or deterioration.
There is more information on this link
You should contact your marine engine supplier for further details.
Engines that are certified to International Standards, i.e. ISO 16147 for diesel, ISO 15584 for petrol, are acceptable since these Standards support the Recreational Craft Directive. It's recommended that you bear these Standards in mind when buying an engine. [2.14]