TANK MATERIALS

Boatbuilders have used a variety of materials for building diesel fuel tanks.  In the case of boats built of steel or aluminum, their tanks are often built into the hull, taking full advantage of space deep in the hull for fuel capacity that otherwise might be wasted.  Many fiberglass boats have tanks built from any one of several metals, the most common ones being aluminum,  Monel metal (an alloy mainly of nickel, copper and iron), stainless steel, steel, and black iron.   Black iron was favored for many years because of its ability to resist acids, but these tanks are often known for their rough, rusty exterior appearance.  Your black iron fuel tank, however, doesn't have to be an embarrassing eyesore or a weak link in your auxiliary power system.

REFINISH OR REPLACE?

Not all yacht builders provide for the need to remove tanks without tearing the boat apart.  Most tanks that can be removed from a bilge compartment without entailing a carpentry nightmare, can also fit through and be lifted out the companionway hatch.  Before starting, remember the old adage "measure twice, cut once."  Check your measurements and consider making a dummy tank from cardboard to check clearances.  These tanks are often odd shapes to take advantage of irregular bilge spaces.  You can achieve good results by refinishing your existing tank, but the primary objective is to assure reliability of this crucial part of your boat's fuel system.  Aside from the tank's current condition, other factors to consider in your decision to refinish or replace a tank are its age and history, how well your existing tank meets your needs, and what you can afford.

FUEL  MANAGEMENT

The fuel we put in our tanks can easily become contaminated.  In fact, it is impossible to completely eliminate contamination, so we must deal with the fact that the diesel fuel in our tank(s) contains microorganisms and some water.  These are the ingredients leading to problems with our fuel systems. While fuel filters and additives can limit growth of micro-organisms, we must take other steps to minimize their potential to get out of hand, forming a soup in fuel tanks.  Microbial growths present two main risks.   The sludge they form clogs filters and injectors resulting in an engine that runs poorly or not at all.  Even if the fuel system isn't clogged, the by-products of bacteria metabolism can attack the tank metal.  There are also problems with water in fuel as it allows rusting in steel and black iron tanks, creating sediment.  Water supports microbial growth which we know is not good.  Finally, there is a risk from sediment clogging fuel lines, filters, and injectors.  

Many of us heading off on an extended cruise want to carry extra fuel which is often carried in polyethylene jerry jugs, or a flexible coated fabric tank, such as those made with denier nylon with an odor resistant neoprene/nitrile coating.  It has been my experience that no matter how careful we have been in purchasing fuel, the fuel in our jerry jugs seems to develop microbial sludge, requiring filtering before we add it to our main fuel tank.  To assure our fuel in the main tank remains as clean as possible, we use a "Baja Fuel Filter" funnel to filter all fuel that goes into our tank.  This takes a little longer and may not be practical for those that have a large fuel capacity, but it works for those of us with patience and fuel demand of less than 50 gallons at the fuel dock.  

The Baja Fuel Filter, available from marine suppliers, looks like a 16" long, round aluminum muffler and tail pipe assembly.  It includes two extremely fine stainless steel screens, and a final third screen that filters out water.  This filter doesn't remove microorganisms, but it does remove the unwanted contaminants that can cause immediate problems.  Our next defense against engine-killing sludge adding the correct amount of an anti-microbial agent to inhibit microorganisms.  We are very conscientious about these fuel handling practices, and though we can't prove they are absolutely necessary, we have never had a clogged fuel filter. 

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