No Cheap Substitutes for Diesel Fuel Lines!

Engine-side fuel lines on a marine diesel are under high pressure, with specialized end fittings. Do not try to replace them with metal brake lines.

29th August 2013.
By Ed Sherman

Question: I’m in the process of getting ready for an extended cruise to the Bahamas over the winter and am trying to get my boat ready for the trip. Part of my preparation is to make sure I have some hard-to-find spare parts on board for my engine and other mechanical systems.

The fuel lines that the red arrow is pointing to are not prone to failure -- they should last for years. Save your money for spare belts, filters, and impellers.

The fuel lines that the red arrow is pointing to are not prone to failure — they should last for the life of the engine. Save your money for spare belts, filters, and water pump impellers.

The photo I sent in of my diesel engine shows an arrow pointing to the diesel fuel lines on my engine that, because of their odd shape, I’d like to keep spares for,  just in case. The problem is, I just priced these lines from Vetus and discovered that the price for the original equipment replacement lines is really high. They are just metal tubing right? Could I just go down to the local auto parts store and get some metal brake lines and change out the end fittings and bend then to the same approximate shape and keep those as spares?

Answer: Absolutely not! First of all, the photo you sent in shows a pretty new engine that is fresh and clean with everything nicely painted. The odds of one of those fuel lines failing is really very low; so, I wouldn’t worry about those lines failing until way into the future. But either way, you need to understand that the lines you are pointing to in your photo are very specialized and have a wall thickness that is several times that of any conventional automotive brake line. Why? The lines are running at much higher pressure, on your engine in the range of 3,000-4,000 psi! Further, the end fittings are shaped to fit the injectors and injector pump they are attached to — quite specialized. Never, ever think that you can jury rig one of these lines with any degree of success!

Again, I really feel that spare fuel lines are really not needed, as everything is so new.  With good care and keeping paint refreshed to ward off rust, those lines should last as long as the engine, but if you must get replacements, see if you can find some good-condition used lines to save money, as they are quite expensive for sure.

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About the author:

Ed Sherman

Ed Sherman is a regular contributor to, as well as to Professional Boatbuilder and Cruising World, where he previously was electronics editor. He also is the curriculum director for the American Boat and Yacht Council. Previously, Ed was chairman of the Marine Technology Department at the New England Institute of Technology. Ed’s blog posts appear courtesy of his website, EdsBoatTips.

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