DIY fuel polishing in practice.

[Maine Sail]

I designed and installed a fuel polishing system for our boat when we installed a new fuel tank. Since installation the tank has been spotless.

It turns the fuel at about 72 GPH, on a 35 gallon tank, and filters down to 2 micron. It passes through a Racor 900 and uses a Carter fuel pump. I have it set to come on when ever the engine runs as well as a second switch to turn it on without the engine.

The polishing pick up was designed to be at the absolute lowest part of the tank and picks up within 1/8" of the bottom.

These are the tapping layouts with rough dip tube lengths:

The polish return comes into a baffled chamber with a return dip tube so the return fuel is deposited back into the tank below fuel level. This has 100% prevented any foaming with the high turnover system.

The pump and polishing filter:

I think I have about $340.00 USD into the parts for the polishing part of the system, and that is going with an expensive filter housing.

 

[pcatterall]

And very nice too!! I will be tapping out for bulkhead fittings and fitting pipes into my running tank next month. Fortunatly there is a large inspection cover so I can drill out ( and catch any bits!!) hopefully I will be able to use the polisher to transfer fuel from one tank to the other as, at themoment this is just done with a connector pipe from the bottoms of the tanks.

 

[Heckler]

And very nice too!! I will be tapping out for bulkhead fittings and fitting pipes into my running tank next month. Fortunatly there is a large inspection cover so I can drill out ( and catch any bits!!) hopefully I will be able to use the polisher to transfer fuel from one tank to the other as, at themoment this is just done with a connector pipe from the bottoms of the tanks.

a tip, smear the driil bit heavily with grease, it then catches most of the swarf!
Stu

 

[pcatterall]

Cheers Stu!
To return the number of passes required I have read the article recommended by Boreades above.
Tha author of that quite technical 'report' gives a good explanation of how multiple passes continually improve fuel 'purity'.
He indicates that using say a 10 micron filter on the first pass a large portion of particles above that size will pass through the filter. Subsequent passes will reduce this portion. After 20 (!!) passes even particles down to 2mm will have been eliminated.
My 5 passes certainly seemed to progressivly 'improve' visual ( at least) quality from being like used engine oil to looking fine!!