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cruisingmom 01-24-2010 09:08 AM

Home Made Diesel Polishing System Q
Hello All
I have a Whitby 42 with 3 70 gal tanks. I know one tank has some sediment but the boatyard wants $300 just to polish one tank. I am thinking of building a portable polishing system that I would insert into my line (Y valve prior to my existing Racor 500FG with shut off) to perform periodic polishing of tanks (beginning of season and maybe during long cruises). My idea is to purchase a second 500FG (60gph /15 psi max- love this filter), and a WALBRO FRB-20 (33 gph / 2-4 psi) with enough hose to run to my deck fill ports for recirculation. My questions are:
1) do I need a pressure regulator on the Walbro
2) running about 15 ft of hose from filter back to tank (~3 ft rise) would this be a problem
3) Walbro has a screen 70 micron filter at bottom - will this be an issue with clogging for general applications and will I need a pressure gauge on walbro
4) Am I missing something or does this seem reasonable
Thank you all

night0wl 01-24-2010 09:12 AM

Why specifically this Walbro pump? Just my curiosity. I have a half way done project to do the same stalled when I couldn't source a pump.

klem 01-24-2010 10:19 AM

I know a few people who have built these rigs for themselves and it ends up being relatively expensive to build one that works well. Since the goal is to get all of the sediment out of the tank, you need to be able to agitate the tank well. The flow rates that you posted above look quite low to me to be doing this properly. Unfortunately, higher flow pumps like the FASS high flow pumps are extremely expensive (~$500). You do not need a pressure regulator as long as the pump is rated below about 50psi.

Regarding filters, a lot of people use filters made for water systems as the first filter in the line since they flow really well and are cheap. If you need to get your flow rate up and don't want to go with bigger filters than you have posted, running a few in parallel could work.

Ideally, you would have access at the top of your tank so that you could direct the returning fuel stream into different parts of the tank. Since this is often not possible, you can often fish the return hose around in the tank a bit to get it to spray in different directions.

I am not particularly surprised at the cost you quoted. These rigs are expensive to build and the filters are expensive to keep changing. Unless you get bad fuel often, you should not need to do this on a regular basis so it might well be cheaper to just pay the money. The best way to prevent it in the future is to filter your fuel before it goes into the tank and use biocide from time to time so that you catch any algae growth early.

xort 01-24-2010 10:36 AM

You should get the pick up hose all the way to the bottom of the tank. If you use the fuel pick up for the engine, you will miss the worst of it. A fuel pick up typically does not go to the bottom of the tank precisely to avoid picking up crud that has settled to the bottom.

I'm not at the boat but I do have a walbro pump that works well. It moves a gallon per hour through the filter and back to the tank. Mine was set up with a dedicated line to the bottom of the tank and the return line dumps at the top of the tank.
Do you have an access port you can open? It would provide you the ability to stir the contents and better allow the stuff to be sucked into the polisher intake.

cruisingmom 01-24-2010 06:07 PM

Responses to questions and more
Thanks folks for responding
I chose the Walbro because it was a marine rated diesel 12V pump with a separating screen filter on its intake for primary screening of junk (70 micron) prior to the RACOR. I think that this is a good match with the racor since the pressure and fuel flow match the racor 500fg pretty well.

I also chose the Walbro because of the low psi but seeing the rating on the RACOR of 15 psi says that I could probably put some more pressure to the system however I would limit it to 10% less flow than the Racor is rated for which is 60 gph. Your input regarding placement of hose in the tank is right on. My issue is that I bought the Whitby last summer and on my delivery home I noted that the port tank dropped quite a bit of black crud into the RACOR when turned on. I believe that the fuel tanks are baffled and there is no real clearance at the top of the tank (fiberglass with aluminum top) to get access. I figured that if I have 45 gallons in the tank and I am polishing at 40 gallons per hour I can run it for a few hours to turn over the tank a few time and try to clear it out. I always use a racor funnel when I add fuel and almost always add fuel from jerry cans so that I can limit the flow.
I know my starboard tank is clean and have added biocide, stabilizer, and cetane boost to all tanks. My keel tank I believe is a design flaw after 30 years and I will not be using it - might empty it and fill with antifreeze.
I am getting the boat ready for an extended cruise and thought that it would be a good idea to have polishing capability on the boat.
I will try to place the return hose to the bottom of the tank and do as much stirring as I can on the hard.
Thanks for all the input and please share any additional insight you might have

night0wl 01-24-2010 08:16 PM

Where are you sourcing your Walbro pump from?

xort 01-24-2010 09:03 PM

All the pumping you do might not budge the sludge in the bottom. I'd look for some way to get the gunk into suspension. Perhaps run an air hose down the fuel fill all the way to the bottom?

My boat came with the system installed. Don't know if mine is set up the "right" way but my walbro pump sucks the fuel through the racor rather than push it into the racor.

cruisingmom 01-24-2010 09:43 PM

Good Input Gents - Push or suck
I priced the Walbro pumps through Walbro Electric Fuel Pumps for Street and High Performance from So what Walbro pump do you have and are there others out there that have a perspective on having the pump before or after the Racor - Since the Walbro has a 70 micron filter prior to pumping maybe this is the reason for putting the pump before the filter and pushing\


klem 01-24-2010 09:56 PM

I would suggest reevaluating the pump. Fuel pumps are made to keep good pressure with a relatively low flow rate. Even with just a hose on the end, you will find that the flow rate is not that impressive (1 gal/min) and will not dislodge any material or properly agitate the tank. Try filling a milk jug in your sink in one minute and you will find that the flow rate is quite low. By comparison, a garden hose is on the order of 4000gph. You will not see the 15psi as quoted by the manufacturer because you are not providing the necessary resistance. The most powerful pump that I know of that is made to be an inline fuel pump is a 260gph FASS which still won't agitate things all that well.

And of course, if you go up in pump size, that means the filters need to be increased in size and flow rate or put in parallel. Make sure that any connections that you make will flow well because any restrictions will make a huge difference in the flow rate.

klem 01-24-2010 09:58 PM

Regarding pushing versus sucking, you always want to push with a pump. If you suck, you place the fuel under negative pressure which is not as effective and has practical limits (this is the reason that wells with surface level pumps cannot be very deep). Pushing, the pump will last longer and give better flow.

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