"Sludge" in Racor

Doing some detective work on my buddy's CHB 34. The primary Racor filter has some visible "sludge" in an internal part of the housing inside the bowl. The bottom of the bowl is apparently clean. This looks like trouble brewing to me and I wonder if this is indicative of a particular issue with the fuel. We don't know the age of the fuel in the tanks or what additives may or may not have been added along the way. We do know the boat was probably lightly used over the past 5-10 years and probably only ran in calm lake water. Since my buddy took ownership it's only seen one freighter wake bow on and got rolling from a wake pretty good once at anchor. So it hasn't been operating in conditions that would really stir up the tanks. Motor is a single Lehman 120.

Question, is this a common sight to a particular fuel issue?

Is that a fuel line rated rubber hose?
Have you removed the sludge what does it appear to be?
I just changed racor filters and wondered why as everything was clean. I do not think that is normal.

Looks like it's doing its job to me.
I have something similar though not as bad
Paper filters are spotless
3 monthly samples from the crud sump show no contaminant

Not sure about the hose but it's getting replaced soon with a new dual Racor setup. Have not opened up the filter to inspect said "sludge". I am not sure why it's hanging/resting up on that particular part of the filter and not dropping to the bottom of the bowl.

Simi, good to hear you have seen something similar but still have clean filters.

I use Biobar JF additive to keep sludge at bay

Hum-bugs live in the water phase of a fuel tank and feed off of the fuel developing dark, slimy gel-like mats.

As these colonies of bacteria and fungi grow (potentially at a rate of doubling every 20 minutes), they can quickly clog fuel filters, plug injectors and lead to excessive sludge accumulation.

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Could be from the tank, could be from the hose, either way it has to come out. I have found that Racors do not backflush very well. You will need to remove the canister and clean it out. It's not a bad job.

What is that screw and locking washer at the bottom. The Racor did not come from the factory with that.
pete

I am guessing the bolt used to hold the metal heat shield.

Hard to tell what the sludge is, it usually falls to the bottom. If sludge but engine runs well...filter system is working and catching what has formed in the tank over the years. On a Lehman 120, the fuel flow is so slow the sludge doesn't get as swirled as Racors like.

Completely normal for the filter, not so much for what could be in your tanks.

Bio or helps but not sure how much it helps with asphaltines versus biologics.

I've had that in the past. Just shut off the fuel flow, loosened the top, drained the fuel out the bottom, dropped the bottom half by removing the screws midway, removed the filter from the top, disassembled and cleaned everything, reassembled, put a new filter in refilled, refilled, put the top back on and tightened down, and turned the valve back on. I didn't need to replace the middle gasket, just those that came with the filter.

Took less than an hour.

It didn't seem to be causing a problem in my case, either, but figured why wait for one?

I had similar sludge when I got my boat, the original fuel was still in the tank after sitting for almost ten years. I pumped out the fuel into drums, and put new fuel in. The agitation of running in seas broke everything loose and it went into the fuel filter as sludge. It has never happened again, so my guess is it formed on the sides of the tank and was broken loose by agitation.

The good news is that the current sludge in the bowl isn't in the tanks anymore, the question is how much more sludge is there in the tanks? I would run the boat in seas to agitate it, and see what else breaks loose, with maybe a half a tank of fuel so there is room for it to slosh around. Take extra fuel filters just in case you restrict the flow too much.

Our boat sat for a few years as well before we bought it. Think I emptied our Racor four times before things started running clear and the first two times had a lot of crap in there.

The metal heat shield is held on by the drain bolt on the bottom. Never seen a screw like that in a Racor before. They come with a plugged hole for a WIF sensor but the plugs look nothing like this screw. I think I would get a new bowl and replace that bowl.

RedRascal said:

Not sure about the hose but it's getting replaced soon with a new dual Racor setup. Have not opened up the filter to inspect said "sludge". I am not sure why it's hanging/resting up on that particular part of the filter and not dropping to the bottom of the bowl.

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Hi RedRascal. The "sludge" is likely asphaltenes, common in almost everyone's diesel fuel tanks, to some degree or another. That the asphaltene remains trapped in the rotor portion of the Racor could mean either poor maintenance of the Racor, high asphaltene content of the fuel, a filter oversized for fuel flow on a Lehman 120, or ???.

Easy fix is to simply rebuild the Racor. Can be done in place (and yes, it's a bit of a mess), or the filter assembly reefed out of the boat, and the rebuild done on the workbench. Racor sells all the parts needed, for a reasonable cost. And then periodic inspection and maintenance as required, of course.

And while the dual Racor unit is a nice upgrade, it is (IMHO) overkill (and expensive) for many of us. A vacuum gauge upgrade to the existing assembly, as part of the rebuild, would be my suggestion. And yes, making sure ALL fuel lines are USCG-approved is a REALLY good idea.

Regards,

Pete

Don't buy Racors with too high a fuel flow rating. The turbine effect doesn't work with low flows in a high flow housing. The blades are there to spin the fuel that aid in separating water and debris from the fuel. At low flow rates, it's just a gravity filter and that's why the sludge settled on the blades.
The right fuel additive will dissolve sludge over time, kill organisms, and allow the filter to catch the in solution debris. A good additive will also help separate out water. Water, and the organisms in it cause sludge (along with buying dirty fuel).

Pete Meisinger said:

What is that screw and locking washer at the bottom. The Racor did not come from the factory with that.
pete

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Yes, it comes with a drain, so water can be let out. Some, as this one, have an aluminum drain, some have black plastic.

The sludge is to let you know it is doing its job and it may be time to change the filter element and clean the bowl. Quite common, nothing alarming.

Great info, thanks. My concern is getting out on a trip with my buddy in choppy seas and clogging the filter. It seems like a few of you have been in a similar situation of not knowing the condition of the tanks and making it without clogging a filter. We're going on an outing in a couple weeks so we'll see how goes. If it's calm I know well be fine but if it's choppy we may be doing an unplanned filter change. I believe he's swapping in the dual racor and hoses the first part of July so the days are numbered for the current setup. I will pass on the feedback of the filter GPH being matched to the engine for the racor to perform optimally.

I doubt that any engine in a CHB will flow enough fuel to make the turbine effect work well. But Racors still seem to work just fine with low flow anyway. If he has a Detroit engine then it may flow enough, but Lehmans or Perkins don’t return much fuel so the flow is generally much less. I have Lehmans and my Racors work just fine.

Now is a good time to do a racor filter change and fuel system air bleed. It's something every diesel trawler owner needs to do. The sooner the better since the filter condition is still unknown.

RedRascal said:

Doing some detective work on my buddy's CHB 34. The primary Racor filter has some visible "sludge" in an internal part of the housing inside the bowl. The bottom of the bowl is apparently clean. This looks like trouble brewing to me and I wonder if this is indicative of a particular issue with the fuel. We don't know the age of the fuel in the tanks or what additives may or may not have been added along the way. We do know the boat was probably lightly used over the past 5-10 years and probably only ran in calm lake water. Since my buddy took ownership it's only seen one freighter wake bow on and got rolling from a wake pretty good once at anchor. So it hasn't been operating in conditions that would really stir up the tanks. Motor is a single Lehman 120.

Question, is this a common sight to a particular fuel issue?

Click to expand...

Diesel fuel has minute parts of heavy distillate ends (basically asphalt) in it. Over extended periods of time it can accumulate. I have seen it twice in my life. Once I had to remove the Racor housing and disassemble it on a bench to remove the filter cartridge.

Change all the filters. You cannot see inside them. Remove and clean out the bowls too.
Also I suggest installing a fuel polishing system on board the boat.
10+ years ago, no one objected (in the condos) if the bladders were unrolled, used during dock side fuel polishers. These days, I'm not sure if walking and sneezing is permitted outside the boat. I suspect the current condos don't fully understand the need to run the main engines and generator every now and then. I have heard complaints that ran from diesel smell to "your boat is block my view of the water." I bought my 75ft slip in a particular place so I didn't block any condo views. Now I have both a 75ft slip and a 55 ft slip. I still dont block any views from the condos.
Someone needs to 'splain to the condo owners, this is a marina and marinas have boat and sometimes boats to smell when first started.

Best Racor article online

https://www.racornews.com/single-post/2016-1-25-mythbusters-fuel-filters


Explains all you need to know.

alvasurg said:

https://www.racornews.com/single-post/2016-1-25-mythbusters-fuel-filters


Explains all you need to know.

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Now this is a great contribution to the forum!
Thanks!

My 1976 trawler had accumulated asphaltines to the point that you could feel them with a dipstick. Made rough water a little more tense thinking about the stirring up the particles and plugging the Racor. Finally had the tank pumped out and fuel polished. Now, after two years on the same filter, no particles and the Racor gauge hardly moves.

I had the 300 gal tanks cleaned on my 43 Ocean Alexander. They were opened and a man went inside and removed 5 gal of red sludge from each tank. I recently took the boat in a 700 nm trip across the Sea if Cortez and had some lumpy seas for a few hours. Some sludge appeared in the Racors. I will have the fuel polished and tanks inspected before my next trip.

Once you have sludge in your tank the Biobor treatment is useless until you have your tanks polished and start from a clean sheet. If you continue to use Biobor treatment in this case it exasperates the sludge problem and does not cure it or add any value to the process.

If your tank is infected it will require a different additive.

Ultimately you should have the fuel tank polished for peace of mind, getting caught in rough water and low fuel levels can become an unwanted and potentially dangerous situation.

alvasurg said:

https://www.racornews.com/single-post/2016-1-25-mythbusters-fuel-filters

Explains all you need to know.

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Yes this is great article, thanks for the reference and good on Racor for posting content like this. It would be another world if all vendors had the means to post this type of content.

As for my buddy's fuel situation it is pending and may be so for awhile. I think he'll monitor the filters to see if they pick up less sludge each time he does a change. The boat is mainly operated in calm waters. This is part of the problem because the boat hasn't been in any seas to stir up the tanks. So far the stirring has been limited to one trip where we caught 2 wakes from ships. It's encouraging to read that some of you have been able to get your tanks to clear up in time. I am sure he'll get the tanks cleaned if he keeps getting sludge in the filter.

RedRascal said:

Yes this is great article, thanks for the reference and good on Racor for posting content like this. It would be another world if all vendors had the means to post this type of content.

As for my buddy's fuel situation it is pending and may be so for awhile. I think he'll monitor the filters to see if they pick up less sludge each time he does a change. The boat is mainly operated in calm waters. This is part of the problem because the boat hasn't been in any seas to stir up the tanks. So far the stirring has been limited to one trip where we caught 2 wakes from ships. It's encouraging to read that some of you have been able to get your tanks to clear up in time. I am sure he'll get the tanks cleaned if he keeps getting sludge in the filter.

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Then he should make sure he is proficient with filter changing and system bleeding if necessary.
His fuel system will be fine, until it isn't.
He just needs to be prepared.
I have that T shirt.