What We’ve Been Reading:
Fuel Systems – What Grows in the Darkness of Diesel, p. 36
By Nigel Calder

Professional Boatbuilder, April/May 2018

Calder, widely known for his essential DIY mechanical and electrical manuals, is back with another editorial in a recent issue of Professional Boatbuilder. The subject matter explores your diesel fuel tank and the fouling that can occur with the advent of ULSD (Ultra Low Sulfur Diesel) fuel.

The article describes two occasions in which Mr. Calder experienced diesel fouling while cruising abroad: In the UK, where he took on a tank of water-saturated diesel, and again in Sweden, where the fouling was so extensive that he was forced to empty and clean the tank. In his usual fashion, these anecdotes highlight some of the most important “gotchas” boat owners run into when dealing with modern diesel. He explains how biodiesel additives can hold a significant amount of water in suspension and even act as solvents for some of the microbial build up on your tank walls. Perhaps most alarming is how removing sulfur and adding biodiesel can create a favorable environment for growth in your fuel tank!

If you own a diesel marine engine, this article is a must-read. Calder provides excellent product references with personal context, and leaves us with a handy checklist for maintaining a healthy fuel system:

  • Sample fuel before it goes in the tank
  • Add a maintenance dose of biocide or biofilm dissolver during fueling
  • Let new fuel settle for a short period before taking a sample from the bottom of your tank
  • Sample fuel in your tank every few months to check for water from condensates
  • Sample your fuel after the boat has been laid up for a period of time
  • Cycle fuel annually
  • Change fuel filters at their prescribed intervals
  • Use test kits to check for dissolved water and bacterial contamination


Click here for a .pdf of the full magazine. Article starts on page 36.