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Capnblu 01-07-2011 03:49 PM

Suggestions for a fuel pump?
I would like to know which 12v fuel pump you would suggest that would provide enough GPM to polish my fuel through a dual Racor setup. I intend to configure the plumbing so that this pump acts as a lift pump while running the engine. The engine is a 4-108 with the regular low, and high pressure pumps on the engine.

jrd22 01-07-2011 05:58 PM

Why would you need an additional lift pump if you have the one on the engine? We have an electric pump in our system with dual Racor filters, but it is only run for filling the filter bowls after changing elements. We can polish the fuel by drawing from one tank and returning to the other through the Racor while the engine is running.
Which pump you would use would depend on how many GPH you want to be able to polish.

sailingdog 01-07-2011 07:48 PM

I would setup the fuel polishing system separate from the regular engine fuel supply. How large a pump you would need depends a lot on how much fuel you're talking about.


Originally Posted by Capnblu (Post 684023)
I would like to know which 12v fuel pump you would suggest that would provide enough GPM to polish my fuel through a dual Racor setup. I intend to configure the plumbing so that this pump acts as a lift pump while running the engine. The engine is a 4-108 with the regular low, and high pressure pumps on the engine.

Capnblu 01-08-2011 01:11 AM

Well, it seems that racor fg 500 filters require 60 GPH flow to separate particulate and water properly. I don't know what engine pushes 60 gallons of fuel past the injectors per hour, certainly not mine. (perkins 4 - 108) (i doubt it would be 1 gallon) Therefore I need an electric fuel pump to polish my fuel while the motor is running. Fuel pumps can deliver this kind of flow, (60 gph, 5psi) and you polish your fuel through the dual racors. I change filters regularily and have a vacuum guage on each low pressure side of racor. When it starts drawing -12hg, it's filter time... I have 2 tanks that are selected by one 6 way valve that is either tank 1, tank 2, or off. The only other valve to open or close is a relief valve (WOG ball valve) from the pressure side of the system into the return line of the tanks (2 - 75 gal). The system is as simple as it can be made, while being able to polish both tanks. If I were to add some valves, I would add the ability to transfer from tank to tank. Till then I will just switch the hose:) So I would like to know what kinda pump you think I should throw in it?

jrd22 01-08-2011 01:28 AM

Can't help you with the pump, sounds like it's going to draw some amps though.

noelex77 01-08-2011 02:45 AM

1 Attachment(s)
I use a small electric fuel pump, rated at about 60l an hour for a bit under 1A. There are loads on eBay etc.
I run this pump on average about 1hr day, but use it more when the tank is stirred up when sailing or if there is a rolly anchorage.It picks up from the very bottom of the tank. I have only had it installed 6 months, but my fuel looks cleaner. I have not measured the flow, but estimate the output about 50l an hour after going through the filter.
I think its better to try and keep the polishing system separate from the main fuel system if possible, although you might consider a diversion system so you can run the main engine from the fuel polishing system in an emergency.
The same pump will work as a priming pump, or emergency lift pump if you want.


Originally Posted by Capnblu (Post 684184)
Well, it seems that racor fg 500 filters require 60 GPH flow to separate particulate and water properly.

I did some research on this when I installed my fuel polishing system. The consensus was that a slow flow rate provided as good if not better filtration and water separation than a high flow rate. There was some opinions that the Turbo spiral for water separation fuel may work better at a high rate, but this was discounted by those with specialist knowledge.

RichH 01-08-2011 11:40 AM

Recirculation polishing filtration is typically best done in an independent circuit with HIGH flow - TANK TURNOVER .... ie. recirculation volume at approx. 3-4 gallons per MINUTE (per 100 gallons of tank capacity) vs. a 10-15M rated filter. This will result, due the many 'tank turnovers', in a residual or resident particle distribution 'in the tank' at essentially 'sub-micronic' levels. A Walbro type impulse diaphragm 'continuous duty rated' transfer pump is the most common and probably the best pump for this type application.
Recirculation polishing is best optimized at HIGH flow rate and LOW pressure drop. Such will ensure that if the tank releases a 'slug' of particulate (breaking loose from the tank walls), the high turnover rate will quickly restore ('recover') the tank back to acceptable particle levels.

Using the fuel line filters + 'return line' & engine's lift pump will accomplish virtually NO 'effective' filtration due to the low 'dilution' (statistical reduction) of particles in the tank as the lift pump on most small marine diesel engines are rated typically for 1-2 gallons per HOUR.

Summary for recirculation polishing : 3 - 5 gallons per MINUTE (per 100 gallons) @ 10-15M in INDEPENDENT circuit - the filter being supplied with PRESSURE (NOT vacuum). Use standard INDUSTRIAL filter cartridges (either pleated or 'graded pore density depth-filters')@ 2.5" or 2.75" dia. X 10 inch length in common industrial filter housing with flat gasket filter seals; expect to pay ~$10-$15 per 10" filter. Performing polishing via the main fuel line is next to worthless due to the extremely low 'tank turnover'. To adequately 'dilute' and maintain the resident tank particles you would need to 'turnover' the tank about 10-20 times .... and at the common .75 gallons per HOUR of a common lift pump would take 20 X .75 X 100 = 1500 HOURS !!! At 3-4 gallons per MINUTE would take 10 to 20 X 4/60 X 100 = 65 to 130 HOURS. Note: if you would use a 2M instead of a 10-15M the above values would be ~10500 HOURS vs. 65 to 130 HOURS (@10-15M) due to the much higher resistance (differential pressure drop) to flow in the 2M filter !!!!

Low flow & very fine M retention will NOT dilute a high particle load in a tank within a 'reasonable' time (Ref. - Newton's Law of Exponential Dilution/decay) ... dont waste your time and $$$$ on low flow and 'tight' filter M to 'polish' a tank.

FYI - Ive been very deeply involved in 'filtration engineering' for over 30+ years.

Pumps: Walbro FR-Series Industrial and Marine Fuel Pumps from


noelex77 01-08-2011 01:13 PM

There are 2 types of polishing 1 uses a high flow rate to blast the tank walls. This requires that the outlet is moved around the tank to scrub the tank walls. (like hosing down a driveway). This type of polishing is done occasionally (every couple of years) and requires opening up the tank to work well. It is usually done by a commercial operator, but you can DIY.
The second type of polishing is done often (maybe everyday) is lower volume and works best when the tank is agitated by boat movement .

In my reading and experience both types of polishing systems can work well.

Commercial operators can only offer the first type of polishing and often imply this is the only option.

RichH 01-08-2011 01:46 PM

Nolex -
I think you are confusing tank 'maintenance' - (regularly cleaning the tank by either mechanical or chemical means) to prevent/remove the deposition of fungal, etc. debris/'crud' - ... with 'polishing' which constantly removes at a fast rate the 'nucleation sites' from the fuel which if not removed then 'grow' (agglomerate) into ever larger and larger particles. Recirculation Polishing isnt a substitute for proper tank 'maintenance' (cleaning, etc.), as polishing is a methodology that extends the interval between 'cleaning' AND reduces the particle load to the in-line filters. Recirculation polishing a dirty or crudded-up tankage is wholly 'worthless' other than in an 'emergency'.

In 'filter-speak' if you have to remove more than 0.05% (wt.) of 'debris' from a fluid, you're not 'polishing', you're 'reclaiming'.

Neither of the methods that you cite are effective for 'recirculation polishing' as neither will result in the 'clarity' and particulate levels of fuel that is needed for a modern diesel engine ... without excessive expense or extremely low over-all removal efficiency.


noelex77 01-08-2011 02:58 PM

I do agree the term "polishing" is a poor one and is often used when it is technically inaccurate, nevertheless we are stuck with this term.
My fuel tank has 2 large hatches each 1m wide so access for cleaning is easy. Many boat owners are not so lucky and have no means of cleaning" the tank. "Polishing" is their only option. Cruising sailors report good success with both high and low volume polishing in conjunction with a biocide, in dealing with dirty tanks and/or diesel "bug" problems.
Mechanical cleaning is preferable, particularly when there is an obvious problem, but not all boats can manage this easily, and for many it involves major surgery. So in the real world many rely on "polishing" to treat and/or prevent problems.

My own tanks dont need mechanical cleaning (yet) and I believe my fuel polishing system filtering the equivalent of the tank volume every 5 days or so and removing any water will at least extend the interval of this procedure.
The engine obviously still needs primary filtration and other measures such as filtering the fuel and checking for water before it enters the tank, as well as a good biocide, are essential.

I am finding fellow cruising yachtsmen are experiencing far more problems with dirty fuel and steps taken to ensure clean fuel will help eliminate what is becoming a very common cause of engine failure.

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