TWL: Fuel Polishing
Rob.Hendershot at invitrogen.com
Wed Jan 22 06:07:18 EST 2003
Forwarded to info at trawlerworld.com since 'captnwil at earthlink.net' appears to
be no longer valid. -Thanks.
> -----Original Message-----
> From: Hendershot, Rob
> Sent: Tuesday, January 21, 2003 10:03 PM
> To: 'captnwil at earthlink.net'
> Subject: Fuel Polishing...
> Just wanted to point out a possible article issue and a special issue that
> occurred on my boat that may be of interest to your readers, due to the
> fuel tank installations.
> In your article:
> How To:
> Captn Wil's Diesel Polishing System
> By Wil Andrews
> in the section Design Considerations you mention at the end "...filter
> replacement intervals decrease."
> "The common system with one secondary and one primary fuel filter tries to
> keep the fuel that enters the injection pump just like new and the only
> effect on the remaining fuel is the returned clean fuel. Once we
> understand that most of our engines return very little fuel to the tank it
> becomes obvious that this system has little or no effect on the fuel in
> our tank. The fuel in the tank keeps getting less and less just like new,
> and filter replacement intervals decrease."
> I believe as the fuel gets older, the filters plug-up more often,
> necessitating the need for more filter replacements. I also believe that
> most installations possibly don't circulate the fuel very well. And in
> fact, boats that simply run in-place (at the docks) or in flat-calms,
> possibly accumulate old fuel in the back sides (away from the pick-up and
> return plumbing) where baffling partitions off rear sections of a tank.
> I too, just after hitting almost four years of owning my boat, plugged my
> fuel filters. The coffee grind looking stuff just kept coming out of my
> selected tank, even though some 'fresh' fuel was added only a few weeks
> earlier. In the nearly four years of running my new-to-me boat I had kept
> the fuel additives going into my tanks and never seemed to have any fuel
> related problems.
> One operational difference that I did start doing within the last two
> seasons was to constantly top-off the boat with fuel. I did so in the
> belief that I would help prevent condensation and water formation in my
> tank. In fact, I have never seen any water accumulation in the filter /
> separators (either before or after starting this practice).
> But now --as Paul Harvey would sort-a-say, I have to tell you the rest of
> my story.
> My boat has four fuel tanks. Two tanks starboard and two port. The front
> tanks are fifty gallon tanks and the aft tanks are thirty gallons. Each of
> the two tanks on each side are connected as a common tank with about a
> one-foot run of 1-1/2 hose connecting an aft tank to a fore tank. This
> gives a total of eighty gallons on the port side and eighty gallons on the
> starboard side, leading to a total fuel capacity of 160 gallons for the
> As the layout would have it, the front tanks are considerably lower than
> the aft tanks. Both the front and aft tanks have the same depth, but the
> top of the front tank comes up to approximately half the height of the aft
> tank. This makes the aft tanks about 1/2 capacity higher, or 15 gallons,
> higher than the fore tanks.
> Now to the gritty details (pun intended).
> The fuel pick up and the fuel return on this system is located on the very
> most forward position of the forward tanks, where the forward tanks are
> just behind the bulkhead for the engine room. I select either to run off
> the port common tanks or starboard.
> Being the intelligent person that you are, by now you have most likely
> figured out the big problem with my system! But just in case, I will
> When I started my practice of "keep-the-tanks-full", I never ran fuel out
> any where near the halfway mark on the aft tanks. At best guest, the fuel
> in those aft tanks have gotten about two seasons old.
> And it then all happened last Sunday while whale watching. As the forward
> fuel tank emptied to just below the 60 gallon mark, for the first time in
> quite a longtime, the slime of coffee grinds slid all the way down and to
> the front of the forward tank that was selected and, poop, I plug my
> number one primary filter to the point no more than about 1000 rpms could
> be obtained. (Or as Marvin Zendler [sp?] "Channel 13, Eye Witness News"
> would say --with a southern-draw, "Slime in the Ice Machine!" I am not
> sure if you know about this Houstonian, but to say the most, he was the
> fellow connected to the Chick Ranch controversy in La Grange, Texas.)
> No problem I though, and I switched to my second primary filter, which
> before it was selected, had a very clean bowl with nice wine-colored fuel.
> Within about 30 seconds (note that the throttle setting was somewhere near
> WOT, but engine rpm before the switch was much less than half WOT rpms)
> the entire bowl filled with goop and the filter plugged to the point the
> engine stopped in a few minutes.
> Note that this is pure speculation. I didn't actually see any
> goop-plugging substance actually slide off the bottom of the aft tank. It
> is possible the forward and aft tanks are of a equally nasty state. But
> the other side of the boat's tanks still have enough fuel to not empty out
> the aft tank. I was able to pull clean fuel out of the other side. I bet
> that when I have consumed enough fuel form those tanks to empty the aft
> tank (this will happen at about 80 - 1/2(30) or 65 gallons --remember the
> aft tanks are about 15 gallons higher than the forward tanks), goop with
> hit again.
> And now the end of my story. I will reengineer the return lines to return
> fuel to the aft tanks and I will add a fuel-scrubbing-recirculator system.
> This system will pull fuel from the forward tank pickups and return fuel
> to the aft tanks. And as suggested, the pull and return will be on the
> same common tanks, such as the port or starboard tankage.
> Otherwise, I will have to wait until the whales go home to have a clean
> tank of fuel and a return of my "safety-factor" (as apposed to a
> BTW, I am thinking I will discontinue the use of that very expensive
> bottle of "X" stuff.
> Rob Hendershot
> Onboard "China Doll"
> 1984 Passport 51
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