Re: Fuel Polishing

Germain Jean-Pierre

Hello Mike,

I have experience with fuel filtration systems and fuel polishing systems. The main issue with fuel in this day and age is the quality of the fuel itself; It ain’t what it used to be!!! The problem also extends to the aviation industry and whilst flying airliners, we never had a problem; the reason is simple, airliners flew 400 hours per month and used a lot of fuel. However, when I started flying corporate jets the situation was different. Typically these aircraft fly less than 500 hours per year and are parked for long periods with near empty tanks … sometimes in moist areas. The bacteria that causes diesel fuel bug is always present in the atmosphere and cannot be avoided. 

Fuel polishing is one means of minimising the possibility of diesel bug contamination and the other is to install a high quality fuel filtration system. Personally I favour basic precautions, a diesel fuel biocide of some sort, full fuel tanks and dual Racor 7550 filters. The diesel fuel pumps on the Genset and the main engine typically feed double the volume needed for operation of the engine. Meaning that 50% of the fuel drawn from the tank is returned to the tank. This is sufficient movement  to ensure that the fuel in your tank is clean. 

The standard precautions are as follows:
-   Keep your tanks full. Always filter the fuel with a good funnel if you have any doubts about its quality. 
-   Add a biocide as directed by the manufacturer. (Biobor or Grotamar are two of them)
-   Relax probably nothing will happen from then on. Of course change the filters when required and verify the sight bowls to guarantee no deposit. 

Installation of a fuel polishing system involves quite a bit of work and sizable quantities of cash. A friend of mine, now stuck in France due to international travel restrictions, asked me to oversee the installation of a fuel polishing system on his boat this year. The installation is successful however his case was different; he had a COVID 19 sized diesel fuel bug problem in his tanks. His boat has large capacity fuel exceeding 1500 L and had been on the hard in Tahiti for an extended period of time due to an unfortunate incident at sea. .. with tanks having a remaining quantity of about 300 liters each. These are perfect conditions for the development of diesel fuel bug. 

System description: consists of Racor fuel polishing pump, a separate Racor 7550 Fuel filter as the pump does not have a sight bowl (although depicted as having a sight bowl on the Racor website, this is not the case ) and you will never be certain of your fuel unless you can visually check from time to time. It also required the design and installation of a cross feeding manifold and distribution valves. This allowed for fuel transfer; a situation which was impossible with the original design. 

On my SM, I opted for the dual Racor filters and I feed through only one of the filters at a time and switch over after each filter change. There is a lot more faffing with the fuel polishing system than with a good fuel filtration system. 

Good luck with your decision and if you require, I’d be glad to talk to you over the Internet. 

Kind regards

Jean-Pierre Germain, Eleuthera , SM007, Opua NZ

On 1 Sep 2021, at 15:54, Bill Kinney <cruisingconsulting@...> wrote:


Many people have installed, such a system, and I'll let them tell you the how's and why's.  

Our boat did two circumnavigations and accumulated over 8000 engine hours with NO primary fuel filter at all, just a water separator.  Despite the obvious success of that arrangement, I did replace the Amel installed water separator with a standard Racor primary filter because it made me feel better.  

I have had sailboats with diesel engines for over 30 years and have never had a fuel issue that a "fuel polishing" system would have fixed.  To be clear, I have also never had a common rail engine that might require a higher level of fuel filtration.

No matter if you have a fuel polishing system, or not, always be careful where you buy fuel.  If the source is even the least bit dicey, use a good quality filter funnel when filling your tank.  Keep the filter funnel clean and dry, and you're very unlikely to have a problem.

Bill Kinney
SM160, Harmonie
Annapolis, MD, USA

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