Latest News

Lessons Learned from 30 Years of CLEANING BOAT TANKS

Lessons Learned from 30 Years of CLEANING BOAT TANKS

Over three decades of cleaning boat tanks has taught us what many boat owners don’t realize until it’s too late—and very costly.

If I had a dollar for every time a conversation started with, “I just bought a boat,” I’d be relaxing on one instead of cleaning tanks. Boat tanks are among the hardest to clean due to their complex construction, tricky locations, and poor design—often with little to no access.

The main source of fuel contamination? Water. Surrounded by water, boats inevitably face issues due to faulty caps, seals, or vents. Additionally, in humid environments, condensation forms on internal tank surfaces not covered by fuel. With water weighing 1 kg per litre, diesel weighing 840 grams, and petrol weighing 740 grams, condensation naturally collects at the bottom of non-pressurized tanks.

Airborne soil spores also enter tanks through natural breathing (expansion and contraction of the air space). These spores are harmless until they come into contact with water, which promotes germination. Spores thrive in heat, much like yeast. Diesel engines, which return up to five litres of fuel per minute back into the tank at high temperatures, create the perfect environment for spores to grow faster.

Another major contaminant, aside from condensation, is fungal material known as “Black Death,” which, along with water, often migrates from bulk storage tanks due to poor maintenance at service stations, marinas, or truck stops. If your tank is made from plastic, fibreglass, stainless steel, or aluminium, and you’re seeing rusty water in your filter, it likely came with the fuel you purchased.

Cladosporium Resinae (or “Clad”) is the technical term for the microbial material that forms at the fuel-water interface. It originates from one or more of the 140+ airborne spores attracted to hydrocarbons during the tank’s natural breathing process. Slimy and sticky like cotton candy, Clad weighs just 1 kg per cubic metre. This means that simply draining or polishing the fuel won’t prevent blocked filters or damage to fuel pumps and injectors.

Boat tanks often have multiple baffles, and Clad will cling to these in areas that are hard to access, even with inspection hatches. The colloquial term for Clad, “Black Death,” highlights how destructive it is. Fuel doctors often refer to it as the “cancer of the fuel system” because it is tough to eradicate once it takes hold. Much like cancer treatment, you must follow a strict treatment regime to eliminate it.

Our Fuel Doctor solution is a detergent-based formula designed to clean hard-to-reach areas in fuel tanks by breaking water and microbial material into sub-micron particles. These are then suspended in the fuel and combusted harmlessly. Two dispersants handle the organic cleaning, supported by a proprietary upper-cylinder lubricity additive that protects pumps and injectors during combustion.

Feel free to call us at 1800-675-077 for expert advice on fuel system maintenance.

Published in print January-March 2025