Micron Rating for Water Separator

[TBOT422]

We have a Racor 500MA water separator on our M35B. There are 3 options for replacement elements 2 micron, 10 micron, and 30 micron. I'm not sure which replacement element that I should buy without taking it apart and see if I can see what's already in it. From what research I've done (after figuring out what a micron rating was) it appears that the downstream secondary fuel filter mounted on the engine (Universal 298854, WIX 33390) is a 10 micron filter. That implies the primary water separator element should either be a 10 micron or a 30 micron. Anyone have any recommendations as to which is proper?

Thanks
Gary
The Best of Times (Hull 422)

[wolfe10]

No question. If you have confirmed that the secondary fuel filter is 10 micron, the primary should be 30.

Brett

[R.B.]

I would actually go the other way. If you look at the little on engine filter, it is not very big in size and I would guess would get clogged very quickly. It is not an easy filter to change when in heavy weather so I would personally go with the Racor filter that would catch all/most of the particles that it could before reaching the little on engine filter. Therefore I would use the 10 or even the 2 micron filter. I also use a vacuum gauge on my Racor to tell me when my filter is starting to get clogged up. No guessing if it is time to replace.

[wolfe10]

Ralph,

Actually, I teach diesel mechanics (over the road applications). The primary filter/water separator is often referred to as the "rock catcher" with the secondary filter the "sand catcher".

Were you to install a 2 or 10 micron primary filter element, that filter would clog up quicker than a 30 and you would be giving the secondary/fine filter a free ride. Were the system designed as you suggest, there would be no reason for two filters.

Brett

[R.B.]

I agree Brett about the secondary filter being useless. I read somewhere, the secondary filter is difficult to obtain and that some people just remove it without replacing it. It really does not make sense to have 2 filters in line. Especially when one is sufficient and easier to change in an emergency. I only have 1 fuel filter on my diesel for the car too. A better system would be to have 2 Racor filters in parallel with a valve to switch to either. I may just do that when I weld up a 2nd fuel tank and install it.

[TBOT422]

Thanks for the inputs.

I'm pretty sure the secondary filter mounted on the engine is a 10-micron. The C36ia website listed several replacement options for the standard Universal 298854 (http://www.c36ia.com/node/1103).

When I looked up the technical specifications for the WIX replacement 33390, it states it is a 10-micron (nominal rating) filter (http://www.wixfilters.com/filterlookup/ ... Part=33390)

I haven't tried to buy the replacements yet, but with NAPA, Purolator, Kubota, and WIX numbers I suspect they should be pretty easy to locate locally. I see them widely available on the internet for around $6 (whereas the Universal filter (probably made by WIX) is about $16).

The 30-micron filter for the Racor water separator makes sense, although the micron rating for both filters is a 'nominal' rating, meaning that the smallest particle they will catch 50% of the time on a consistent basis. There could certainly be an argument that two 10-micron filters in series might be better than a 30 and a 10.

I am a little surprised neither of you (or anyone else) mentioned what you actually have in your boats. I assume we all have the same M-35B with the 298854 fuel filter and some sort of water separator upstream from that one. Is my boat significantly different than all the other C350's? I also sort of expected that something this simple would have been discussed in the operator's manual. I just haven't found it.

Thanks
Gary
The Best of Times (#422)

[wolfe10]

I am a little surprised neither of you (or anyone else) mentioned what you actually have in your boats.
Thanks
Gary
The Best of Times (#422)

Yes, ours is an M35B with 30 micron primary (Racor) and Universal/Westerbeke OE secondary fuel filter setup. I get the secondary filter from our local Universal/Westerbeke dealer-- a routine stock item.

And, while talking about the on-engine secondary fuel filter on our M35B, be aware that there were quite a few fatigue failures of the bracket the secondary filter is mounted on. When it fails, the fuel filter is hanging by the fuel lines-- NOT a good thing, so check it. The new replacement is an improved design.

And, yes, some boat manufacturers (Caliber comes to mind) do install two parallel/series filter systems so if one clogs, all one has to do is open/close some ball valves and instantly you are on new filters and can change the dirty ones at your convenience. A couple of hundred more dollars, but perhaps some worthwhile insurance. On our 350, were I to contemplate this, I would parallel the Racor filter/water separator, with both feeding the engine mounted secondary filter. Ball valves at inlet and outlet of each filter (total of 4) for instant positive switching from one filter to the other.

Brett

[R.B.]

Ah I see where the confusion is, I was thinking of the little filter by the fuel lift pump not the screw on filter on the engine. Sorry. I still use the 10 micron for the Racor though.

[TBOT422]

Brett,

Thanks for the comment about the fuel filter bracket. I was already aware of that from other threads on this board, and of course, mine is cracked. I've already received the replacement from Westerbeke but haven't installed it yet. I will install it when I replace the fuel filters.

So I see we have 1 vote for a 30/10 combination and 1 vote for a 10/10 combination. Apparently it doesn't matter and they are essentially the same price. I think I will go with the 10/10 combination. That combination might produce slightly better filtration, but its probably not necessary. The only down side I see of that is that the Racor filter may become clogged faster if it is a 10 micron versus a 30 micron.

Thanks
Gary
The Best of Times (#422)

[wolfe10]

The only down side I see of that is that the Racor filter may become clogged faster if it is a 10 micron versus a 30 micron.

Thanks
Gary
The Best of Times (#422)

Gary,

Correct. And not wanting the engine to starve for fuel at critical times is why divide the filtration duty. As you suggest, less chance of a clogged filter stopping the engine. If you only cruise in safe areas where changing a filter is not hardship, really not an issue.

But in our trip this winter from Texas to the Abacos and back, there WERE times when an engine failure would have been more than just an inconvenience.

BTW, we run the same fuel filter configurations on diesel motorhomes: Course primary filter/water separator and fine secondary filter-- often with manual primer pump. This is the accepted configuration in the industry.

There are also some "best practices" for diesel fuel: Keep tank FULL. Any moisture in the air in the tank will condense when tank temperature reaches the dew point. And, each day as the temperature rises, air exits the tank through the vent and as temperatures fall in the evening, air (cool, humid air) is sucked back into the tank where it condenses as the temperature again falls to the dew point. Repeat XXX days.

If storing diesel over 2 months in the summer or 3 months in the winter, I add a BIOCIDE. And, if filling in the summer or early fall in an area where the winter temperatures will get below freezing, add an anti-gel additive (from Walmart, etc). If you purchase fuel in the winter, it is already "winter blend".

Brett

[TBOT422]

Brett,

Good point. I suppose it comes down to which filter is easiest to change. Having not changed either yet, I don't have any first hand experience, but it looks like the Racor might be the quickest to change in an emergency (a lean toward the 10/10 configuration).

Right now, most of our sailing is relatively safe. We live in Clearwater, FL and can be in the open Gulf in about 30 minutes. So we are mostly under sail. Of course, docking would be our worst scenario for the engine to decide to quit.

Texas to the Aboacos and back. You had to go right by us. How long were you gone? We went to Walkers Cay in the Abacos via power boat several years ago. I understand your concern about times when an engine failure would be more than an inconvenience. I lost power on our (single) engine in the middle of the Gulf Stream on one passage (electrical problem). Luckily we were making the transit with another boat who helped us out.

That's one of the reasons I am trying to learn as much as I can about our new Catalina so that I can diagnose and implement fixes as quickly as possible. So far, we've only had time for one "shake down" cruise to Port Charlotte and back (about 200 miles round trip). We learned a lot about the weaknesses in the refrigeration system (now much improved thanks to comments on this board), replaced one of the 4 battery banks that couldn't hold up for a week long trip, and battled a persistent small coolant system leak. From what I have observed so far, I suspect it will take me close to a year to find out where all the critical components are and how to diagnose and fix them. Then, of course, some supposedly non-critical item will fail and create havoc. Such is the boating life. My philosophy is that if you're on a boat, and you're not on fire and you're not sinking or at risk of sinking, then you don't have a problem. It's merely an inconvenience.

Thanks
Gary
The Best of Times (#422)

[wolfe10]

Gary,

Changing both fuel filters is easy-- it always sounds more complicated than it is. Best to do it at the dock under no stress, so in an emergency you will not have to learn under duress.

Have the correct Racor filter for the primary filter/water separator and Universal/Westerbeke secondary filter.

The Racor filter comes with new O rings. Open the drain first with an old jar or can under the petcock. Remove the lid, then the filter. If "crud" in the bottom of the filter, I use an old ketchup bottle filled with diesel, one with a squeeze top to squirt loose the crud and let it drain. Lube the o rings in diesel or motor oil. Install the new filter DRY. Yes, you can fill it, but the electric pump will fill it in less than 30 seconds in the last step.

To change the secondary filter (the one on the engine) buy an oil filter wrench sized for the filter. Put paper towel, etc under the filter so you don't get diesel in the bilge (actually in the engine pan). Remove and install the new one-- again use oil or diesel on the O ring.

On the top of the secondary filter is a bleed screw. Loosen it. You then need to activate the electric fuel pump. It can be done using the key. But, it is also easy to disconnect the positive wire near the fuel pump (near primary filter) and touch it to the hot side (large lug) of the solenoid to activate it. When bubble-free fuel comes out the bleed screw, tighten the screw and you are done.

Brett

[sailorbob]

Back when "Second Wind" was new and I was assembling spares, I contacted Westerbeke for a recommendation on the Racor. Joe Joyce, the service manager, replied "Westerbeke recommends a 10 micron filter element be used. We do not like to see anything smaller than 10 micron." That should rule out the 2 micron and 30 micron options. I don't believe the fuel filter on the engine comes in different filtration sizes. Am I wrong there? Also, the engine fuel filter bracket with the correct bend (rounded rather than knife edge) can be obtained from Westerbeke - it's a pain to replace because the hoses are in the way, but not impossible. Ratcheting open end wrenches help.

Bob
"Second Wind" #301

[wolfe10]

Bob,

Having worked with OTR diesels for 30 years, I would love to hear the reasoning behind installing a 10 micron primary followed by a 10 micron secondary filter. Would make a good story.

Brett

[sailorbob]

Joe Joyce's email is JJoyce@westerbeke.com. Perhaps he has an explanation. But have you confirmed that the engine-mounted filter is in fact 10 microns? I get confused by the "primary/secondary" terminology - which filter is primary and which is secondary?

Bob

[Triumph]

Wow, lots of opinions on this one. Since we're voting, I vote for the 10 micron primary (first, Racor) filter, and a 2 micron secondary (on the engine). This kinda goes along with the rocks and sand comment made.

[wolfe10]

Joe Joyce's email is JJoyce@westerbeke.com. Perhaps he has an explanation. But have you confirmed that the engine-mounted filter is in fact 10 microns? I get confused by the "primary/secondary" terminology - which filter is primary and which is secondary?

Bob

Fuel flows from fuel tank to PRIMARY fuel filter (Racor) to electric lift pump to SECONDARY fuel filter (on-engine Universal/Westerbeke) to injection pump.

I also e-mailed Joe and asked for him to comment on this discussion. Look forward to his comments.

Brett

[TBOT422]

Triumph,

As far as I can tell, you do not have any choices for the secondary filter mounted on the engine. And as best as I can tell it is a 10-micron filter, so a 10/2 option is not possible.

Whereabouts in Tampa are you? What year 350 do you have? We live in Clearwater, and recently purchase a 2007 model. Maybe we'll run into each other some time.

I can't wait to see Joe Joyce's comments.

Gary
The Best of Times (#422)

[sailorbob]

Brett, did you ever hear back from Joe Joyce at Westerbeke, for an explanation of his choice of fuel filters?

Bob
Second Wind #301

[wolfe10]

Bob,

Your fuel system is as follows:

Fuel tank to PRIMARY fuel filter/water separator (Racor) to lift pump to SECONDARY fuel filter mounted on the engine (Universal/Westerbeke) to injection pump.

If all the hundreds of diesel applications I am familiar with, the primary filter, since it is the first one the fuel gets to is the course filter. In fact, many refer to it as the "rock catcher". The secondary is the fine filter (smaller micron rating).

To use two of the same micron rating means the primary filter will clog up MUCH faster, since it is catching not only large, but all particles down to it's micron rating. AND, the secondary filter serves no function if it is the same micron rating as the primary filter. Since filters are generally replaced at the same time, it makes no sense to clog up one quickly and give the other one a free ride.

Brett