Fuel Filter Question

It's good to have a secondary. Changing elements on a racor can let a "burp" of crud flow downstream. Also, as racor elements age, they can loosen on the central post and let crud through. I'd put a secondary back on.

I agree Ski and did replace my nightmare twin OEM filters with a simple Racor 120 spin on bolted to the same flange the other engine mounted ones (downstream) of the lift pump. I was concerned with the lift pump coming apart considering the design tech there.

Yet Daddyo's revelation once again shows that while maybe not conventional, that many other "methods" out there that aren't in the manual, not in boating mags, not recommended by a pro, etc..etc...do not necessarily mean the early demise of your engine (if similar) and possibly no long term effects either. So for emergencies or temporary use, it may be just fine. For long term effects, you would need a bit more info or wait for Daddyo's long running trip thread circa 2030.

Daddyo said:

In my opinion the filters on the engine are unnecessary with a modern filter like the Racors. The primary should be all that is neccesary.

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If that is true how do you explain the fact that when changing filters you sometimes will see residue in the bottom of the CAV filter bowls even with a Racor up stream of them?

Ski in NC said:

It's good to have a secondary. Changing elements on a racor can let a "burp" of crud flow downstream. Also, as racor elements age, they can loosen on the central post and let crud through. I'd put a secondary back on.

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I do agree that the "burp" issue is a remote possibility. I did not mention that I use switchable Racor 900s for filtration. I think I will revisit my decision, thanks.

Just a few observations from a Rolls Royce trained diesel engineer on multi fuel diesels.
Why are you guys so obsessed with Raccor Filters ? do you all have shares in the company ? or is the fuel in the US of A so badly refined ?
Start at the beginning, clean your diesel tanks, if possible fit a sump drain tap, or do so at the first opportunity. Keep diesel tanks full over the winter period to stop condensation. As part of your engine room checks drain a small amount from your diesel tank sump drain every week into a clear glass receptacle as a check, you will see any water/condensation/fine sediment. Note ! to do this efficiently just 'crack' the valve ie open it very slightly until only clean fuel runs.
The reason for this is that if you open it fully you will break the surface tension of any water present and only get what is at the orifice opening. If you do it slowly the surface tension will keep the water globules locked together and they will be drawn to the opening.
Question. Why do trucks not have this problem ?
Because they use fuel virtually immediately it's put in the tanks and if a tank looks dirty it's taken off and cleaned as part of service routine.
Now the explanation because some guys just don't get it.
Diesel fuel, like fine wine, contains sediments and moisture not removed during the refining process and a truck diesel engine will burn this off as a matter of course as they are designed to do and it's not harmful, many truck engines can do up to a million miles in their lifetime.
A pleasure boat engine however will never achieve anything like this and can last indefinitely if maintained correctly.
The fuel problems in boats are caused by diesel fuel sitting in a tank for maybe months on end, and, like fine wine, any sediment will gradually settle down to the bottom of the tank, any moisture(water) in the fuel plus any condensation will also settle to the bottom of the tank.
Diesel bug just loves this interface of water/fuel and will proliferate until the whole tank is contaminated.
If there's no water in the tank, the bug can't breed !
The moral of the story is clean your tanks, and keep them clean.
If you have gold plated triple banks of quadruple Raccor filters THEY WILL NOT CLEAN THE CRUD AND MOISTURE FROM THE BOTTOM OF YOUR TANKS, they will only clean fuel that is circulated by the pumps.
So instead of wasting your money shutting the door after the horse has bolted, roll up your sleeves, get down and dirty, clean out your tanks, fit a small sump and accessible drain cock, you only have to do it once ! drain water/crud once a month as part of your service routine and spend your time sipping a cold one on the back deck instead of constantly changing filters.
I hope my explanation is clear and takes away any ambiguity.

Irish Rambler- your post is dead on. The problem is that many of these pleasure boats do not have a low spot sump, or for that matter any easy way to do a low point drain. Many tanks have no clean out panels, and no access to the tops. So the normal practices for maintaining fuel and tanks is difficult.

That is often what these guys are dealing with. Sometimes the most practical way is to clean the tanks with the primary filters. Certainly not optimal.

When one buys a used boat, as many of us here have done, often one inherits the problems borne by poor maintenance practices of the PO. Dirty fuel tanks is just one example. Even the best of systems can suffer contamination due to unforeseen circumstances. Adequate filtration prevents damage downstream to those expensive machines that convert old dinosaurs into maritime propulsion.

As your post illustrates so well, comparing truck fuel tanks to marine pleasure craft fuel tanks is pretty much meaningless.

Marine tanks don't come out easily for cleaning, many don't have proper access ports, in most cases they don't have stripping ports with proper sumps, they have more internal baffling, the fuel can stay in them for months if not longer than in a truck tank, etc., etc.

So those are some of the reasons proper filtration is more discussed and fretted over on boats than cars and trucks. And with proper sizing you shouldn't be constantly changing out your fuel filters with anything but severely contaminated fuel.

Of course proper filtration isn't as complicated as these discussions might make it seem. But admitting that would take all the fun out of the discussions.

>your post is dead on. The problem is that many of these pleasure boats do not have a low spot sump, or for that matter any easy way to do a low point drain. Many tanks have no clean out panels, and no access to the tops. So the normal practices for maintaining fuel and tanks is difficult. <

You get what you pay for , many trawler style boats were price built so do not have a proper fuel tank, just a metal box with fuel in it.

Sadly even when replacing these iron units , most dont purchase fuel tanks , just another box to hold fuel.

Raycore filter elements are cheap by the box , so they stay popular.

Obviously my previous post raised discussion points to be aired and quite rightly so, we all have different points of view and we're free to express them.
I would point out that of all the boat's I've owned only one came with a sump drain on the diesel tank. All the others I either removed the tank to fit one, or, made an inspection/access hatch in the top to suck out the crud. One nearly beat me until I removed the fuel sender unit on one side of the tank, careened the boat against the dock and vacuumed the gunk out that way.
I have single engine boats and go to sea regularly in various weathers safety is paramount. I would respectfully point out that I've never had to change fuel filters at sea.
Someone mentioned Ford Lehman engines in an earlier post, they are still manufactured in Turkey and parts are freely available.

FF said:

>your post is dead on. The problem is that many of these pleasure boats do not have a low spot sump, or for that matter any easy way to do a low point drain. Many tanks have no clean out panels, and no access to the tops. So the normal practices for maintaining fuel and tanks is difficult. <

You get what you pay for , many trawler style boats were price built so do not have a proper fuel tank, just a metal box with fuel in it.

Sadly even when replacing these iron units , most dont purchase fuel tanks , just another box to hold fuel.

Raycore filter elements are cheap by the box , so they stay popular.

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The interesting thing is when I have opened up baffled fuel tanks to clean them out, I've found the contaminates in them to be mounded up in the bottom center of each baffled area. Which leads me to believe that unless you have a low spot in the chamber of each baffled area that you can draw from, you will not able to get anywhere near all the junk out of of a tank that has only one low spot to strip from.

Apparently Lehman feels that anything smaller than 10 micron will not harm the engine.
In that case I'd remove the Fram and put a 30micron in the Racor. The Racor will catch the big stuff and on engine filter will catch the stuff between 30 and10 micron. Both will last longer that way.

hobbystuff said:

Excuse my ignorance, but previously on my sailboat I only had one fuel filter to change.....

Currently on our boat, we have a Lehman 120 with three filters leading from the tanks in the following order:

FRAM CCS1136 5 micron (seems to be original)
Racor 500FG with 2 micron (looks to be added at some point)
On Engine Dual CAV @ 10 micron (the stock Lehman filters)

This appears to be what is installed in the boat currently, based on the documentation I have.

I seem to have no choice as to the micron rating for the FRAM or on engine CAV units, but the Racor I can choose 2, 10 or 30. Is the 2 micron what should be installed? If so, does that mean my on engine filters aren't doing a darn thing?

Any advice? Thanks in advance.

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This question usually generates a lot of opinions. Diesel as it leaves the refinery is filtered to 30 microns and on the Lehman, that will work just fine. If your tankage is greater than what you typically run through in a month or so of usage, a 30 micron that will return the fuel to refinery spec as primary (first in line) is fine, especially if your OEM filters are 10 microns. With three filters, the sequence would usually be 30, then 10, then 2 micron. A pre tier II engine like yours isn't going to benefit from filtering to 2 microns, so suggesting putting a 2 micron filter as a primary is nutty, IMO, since it will be forever clogging if your tanks are large. My engine is also pre tier II, and for what it is worth we polish at 30 microns, transfer fuel to the day tank at 10 microns where it passes through 2 micron filters before hitting the OEM filters that are whatever they are.

In response to Capt.Bill 11.
Your are absolutely spot on with your comments.
The mounds of gunk are the centre of no flow area's, when the boat is in motion the fuel passes through the baffles and create tiny circular currents and the deposits simply swirl in the same way as a centrifuge and the fine particles settle out and form the mounds in the no flow areas..
I rattled on here about getting tanks out and cleaned as fixing the problem, not the symptoms.
If a tank is out for cleaning it's a simple matter to modify the tank floor to have a 3 degree slope on 3 planes to a central drain point, the normal motion of the boat and fuel passing through the baffles will allow the sediment and water to go to the lowest point, ie the no flow area in the sump, with the angle of the floor of the tank sediment will slide to the lowest point , simply draining this once a month until clear fuel runs into a clear glass receptacle alleviates the fuel problem.

I understand how the water would flow down the slope with the floor of the tank angled toward one spot. But I'm not so sure about all the crud. With the baffles extending down to the bottom of the tank with just relatively small holes cut into the corners of the baffles for the fluid to flow from baffled area to area, I'm not so sure the crud would easily move down hill.

But I could very well be wrong since I've never had the opportunity to open up a tank with a sloped bottom. Have you?

here's mine...the crud was definitely in the bottom of the slope...but the slope was pretty severe.

on many small vessels, multiple drains or a center deep one may not be accessible no matter how great of an idea they are.

I would think if you could clean the tank every 3-5 years relatively easily or after a known bad fuel load..that may be good enough. After I bought my boat I put 3000 miles on it and the fuel and filters always looked perfect...but this crud had been accumulating probably since the boat was new 26 tears ago.

I believe current off road diesel engines are required to comply with EPA Tier 4 requirements meaning they have to use the same low sulfur diesel fuel as automobiles. Do you know what filtering in microns takes place for over the road diesel?

Delfin said:

This question usually generates a lot of opinions. Diesel as it leaves the refinery is filtered to 30 microns and on the Lehman, that will work just fine. If your tankage is greater than what you typically run through in a month or so of usage, a 30 micron that will return the fuel to refinery spec as primary (first in line) is fine, especially if your OEM filters are 10 microns. With three filters, the sequence would usually be 30, then 10, then 2 micron. A pre tier II engine like yours isn't going to benefit from filtering to 2 microns, so suggesting putting a 2 micron filter as a primary is nutty, IMO, since it will be forever clogging if your tanks are large. My engine is also pre tier II, and for what it is worth we polish at 30 microns, transfer fuel to the day tank at 10 microns where it passes through 2 micron filters before hitting the OEM filters that are whatever they are.

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Modern diesels, especially those that are Tier II, III an IV are normally set up this way. Ditto large truck diesels burning +200 gph sometimes eliminating the first stage if the the fuel trucks are filtering fuel as dispensed. A 3 stage setup will deal with badly fouled boat tanks so long as the fuel can exit the tank.

As posted in loving detail by Flywright a year or so ago, there are good ways to have your tanks cleaned.

I have always used something like this: Absorb & Remove Water in Diesel or Gas Tank | WaterWick Fuel Tank Socks | Absorbents | Supply Line Direct (not the brand I use but same idea)

and never had a sludge or water problem. Also my tanks draw from the bottom so any water ends up in the filter not laying in the bottom inch of the tank. My lobsterboat has the original steel tank from 1971.

sunchaser said:

Modern diesels, especially those that are Tier II, III an IV are normally set up this way. Ditto large truck diesels burning +200 gph sometimes eliminating the first stage if the the fuel trucks are filtering fuel as dispensed. A 3 stage setup will deal with badly fouled boat tanks so long as the fuel can exit the tank.

As posted in loving detail by Flywright a year or so ago, there are good ways to have your tanks cleaned.

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And, methinks that if you have a high gpm polishing system of say, > 2 gpm, and you polish the fuel when the tanks are so low you can barely keep from sucking air then you never will have to clean your tanks. I think there is enough real world experience to validate that. I polish when underway with relatively full tanks for drill, but I can't convince myself that I am removing all precipitants from the fuel. Likewise, when I polish on a nearly empty tank in a seaway, I can't convince myself that I am doing anything BUT removing all the crud. And let's suppose I am not removing ALL the crud, although I don't see how I am not. Nevertheless, I am simulating exactly the situation where crudded tanks ever cause a problem and that is when the boat starts tossing and loose stuff starts clogging the filters. So that potential, IMO, is eliminated even if I miss a bit here and there.

I think you're right. Polishing works best, in fact may only work, when your tanks are low and you are underway with strong enough wave action to really get your fuel churned up and the crud suspended in the fuel.

In answer to your question Capt Bill. Any fines take quite a while to settle and 99% will gravitate to the sump.
I have to speak with care here, Red diesel is supplied to agriculture and static plant at a reduced tax rate(in UK & Ire). It has been suggested that some unscrupulous people have been supposed to have removed this dye. Someone told me that they use translucent tanks and can quite readily observe the movement of the fine sediment.
I overheard 2 strangers in a bar discussing the subject.
Any observations I make are purely in relation to legally bought fuel in my own boats.

psneeld said:

on many small vessels, multiple drains or a center deep one may not be accessible no matter how great of an idea they are.

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You might be right. But if you had a hose or pipe run to it or them when the tank was installed leading out and accessible you could solve that problem.

But a steep sloping bottom leading to a sump would be best I would think.

Fine stuff found in the bottom of filters is common as NO media filter can remove the really fine stuff.

Folks that want to avoid all these problems have other choices.

Cheap is a gravity day tank, with a sump. THAT IS MAINTAINED

Better , esp for the few offshore folks is a centrifugal unit like the new small Alfa Lafal that does a better job than media style units.

Most of A-L items are for the commercials , but they do offer items for the white boat folks.

Oil treatment – fuel oil and lube oil separators ... - Alfa Laval

www.[B]alfalaval[/B].com/industries/marine/oil.../Oil-treatment.aspxAlfa Laval


Whether maximizing the energy you get out of your fuel or extending the lifetime of your lubricant, our oil treatment ... Filtration - Automatic full-flow filters, CCU.

FF said:

Fine stuff found in the bottom of filters is common as NO media filter can remove the really fine stuff.

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If it is too fine to get caught in a 2 micron filter, it is too fine to do harm to any engine.

Sumps are a fine idea. I have them, but also a polishing system that I hope is being properly used. In 6 years, the crud I have drained out of the tanks wouldn't fill a teaspoon because it doesn't seem to exist.

>If it is too fine to get caught in a 2 micron filter, it is too fine to do harm to any engine.<

This overlooks the abrasive action on your finely created injectors and injection pump.

Injectors begin to dribble and not seal , from wear.

Based my own experience based on my own usage of diesel fuel in boats and work experimentation over the last 35 years I've progressed through no sump/drain, centrifuge filters, automatic filters, Caterpillar filters, Mild steel/Stainless steel/Aluminium tanks
For both my boats I have tanks with 3 degree slope to sump and drain valve.
The cheapest and most cost effective has been the stainless steel bright annealed fuel tanks with 3 deg slope and drain feeding through a Caterpillar filter/water separator then the CAV 'spin on' to the fuel pump. Regularly Cleaned.
I've never broken down at sea, rebuilt any of my own boat engines, fuel pump, injector overhauls are rare and limited to spring replacement and nozzle cleaning.

Another thought is that most of the stuff that contaminates diesel in our tanks is bio matter and asphaltenes. All relatively soft. They can probably go through the system without causing harm. Probably rare to have some micron sized abrasive in the fuel. Completely my theory, nothing to back it up.