Racor filter size

dlochner · Oct 23, 2023

The RS26T is the 10 micron filter. The coarser filter goes first, the finer filter picks up anything that slipped by. If the 2 micron is first it will block too much and get clogged faster than it should.

If you have small pinholes leaking fuel you are in line for a new fuel tank. They don't heal themselves and polishing the fuel doesn't fix the problem.

Alan Gomes · Oct 23, 2023

Tucson Sailor said:
We have a 1996 Catalina 30 MKIII #6374 with 390 hours on the MX 25 engine. It has the Racor 26RS spin-on filter as the primary, then the engine mounted 2 micron filter followed by the facet filter at the fuel pump. I believe the 26RS is a 2 micron filter. I had the tank polished a few years ago when some small pitholes were leaking. The engine runs fine.

I'm about to change the Racor. I've read that 2 microns on the primary is redundant. Should I switch to 10 microns for the primary Racor? If so, which # spin-on Racor should I install?

Thanks,
Tim

Yes, go with 10 microns instead. 2 microns is too restrictive and is hard on your lift pump. 10 is plenty good enough as far as filtering goes.

jssailem · Oct 23, 2023

You can always check with Universal.

Tucson Sailor said:
the engine mounted 2 micron filter

I believe that the on engine recommended filter #298854 is a 10 micron filter not a 2 micron. Looking up the cross reference filters with the above part number, they are identified as 10 micron filters. Looking at the M25 engine manual no spec is stated.

From a practical standpoint the 10 micron filter (in my opinion) is more than adequate to keep the harmful fuel particles out of your engine.

Here is a reputable source to help with your analysis of the micron size you might need.

How do I choose the right fuel filter?

help.summitracing.com

Stu Jackson · Oct 23, 2023

Forget about the filter on the lift electric pump, it filters nothing unless it is the first in line from the tank in which case you get a very nasty surprise one day. It should be after the primary.

There are two schools of thought on primary / secondary filtration:

1. Primary should coarser, secondary finer - this is borne out by filter manufacturers, who should know

, and everything we mechanical engineers learned in third grade.

2. Primary should be finer, secondary whatever it is, because the primary is almost always easier to access (the secondary is on the engine somewhere hard to get to). This is logical for a use case point of view.

The secondary on Universal engines is as John reported 10 microns, although I've read 25 to 30 in other fairly "researched" reports. I simply approach this as: it is what it is, 'cuz it's what fits on my engine and the equivalents from other filter manufacturers are the same rating.

I deliberately choose to have a finer primary on my boat because I CAN EASILY CHANGE IT.

And the reality is that because the filters we use are rated for much higher flow rates than any of our engines use, it really makes little difference.

I'd rather have my accessible filter clog first. Plus I can ignore changing my secondary for a long, long time.

I ran 2 micron primary for over 900 hours. I changed my secondary after 6 or 7 years. Engine still ran and still runs.

This is after 25 years of owning this boat and having seen and participated in more of these discussions than I could count. :beer:

Richard19068 · Oct 23, 2023

jssailem said:
You can always check with Universal.

I believe that the on engine recommended filter #298854 is a 10 micron filter not a 2 micron. Looking up the cross reference filters with the above part number, they are identified as 10 micron filters. Looking at the M25 engine manual no spec is stated.

From a practical standpoint the 10 micron filter (in my opinion) is more than adequate to keep the harmful fuel particles out of your engine.

It appears the stock on engine fuel filter might be a "25 micron" but we could really go down the rabbit hole with micron ratings. The problem is it is hard to compare one manufacturer's rating with another's.
Here is some interesting old stuff from Maine Sail, AKA RC:

Re: On to the secondary fuel filter!
« Reply #2 on: July 26, 2011, 12:47:34 PM »

If you want to go aftermarket I like the Wix, Donaldson or Baldwin filters. The factory filter is approx a 25 micron, "absolute" according to Joe J. at Westerbeke, and the Kubota, according to my local dealer, is a 24 micron (but I have never heard of a 24 mic paper).

That being said we have no clue what the filtration efficiency is for the factory filters so that 25 micron filter may be at 98%, 99% etc. and would possibly be a 10 micron filter at 50%.... So, it still could be a 10 micron rated filter if you look at different efficiencies.? I do know that Westerbeke on engine filters are 15-17 micron rated and Westerbeke actually publishes this..

If you want to take advantage of multi-step sequential filtering, the primary taking some load and the secondary taking some load, a 30 mic on the primary and the good aftermarket or factory is a fine set up. If you have clean fuel a 10 mic on your primary will be fine and your spin on will catch virtually nothing as it is may already be filtered out beyond that spec. Parker / Racor filters are rated nominally at 95% efficiency so the 10 micron is theoretically capturing 95% of the particles at or bigger than 10 micron.. They consider "absolute" 98.6%-98.7%..

Universal advises against anything smaller than 10 mic for the spin on, though I don't believe you could even find one and of course we don't know if this is absolute or nominal..

Kubota apparently designed this product to run on 25 micron "absolute" filters, but at what efficiency we do not know, so over filtering to 2 micron is not really all that necessary.

« Last Edit: July 27, 2011, 11:59:07 AM by mainesail »

Logged
-Maine Sail

« Reply #5 on: July 26, 2011, 02:50:59 PM »

The problem with equivalents is they are rarely equivalents. The Wix for example is a 10 micron nominal rated filter with no definition of what "nominal" is for Wix. They don't know the "absolute" as I have spoken with their engineering department to try and find that out. The Universal is claimed to be a 25 micron by Joe J. at Westerbeke and the Kubota a 24 micron and some others like Donaldson a 17 micron etc. etc...... Fram simply chooses not to publish any micron specs for the "equivalent" filter? It is hard to know what the equivalent is when it is tough to get a straight answer out of Universal.

Slight changes in micron ratings with oil are one thing but with fuel it can mean injector issues which can get expensive. I suppose so long as the "equivalent" filter is less than the micron rating of the Kubota or Universal filters you should be fine. Of course even my local Westerbeke distributor does not know what the factory micron rating is. I had to email Westerbeke to find out and was told 25 micron "absolute" but as I mentioned above depending upon the efficiency rating it could still be a 10 micron "nominal" filter even if a 25, if that makes sense..
« Last Edit: July 27, 2011, 11:52:46 AM by mainesail »

Logged
-Maine Sail

« Reply #11 on: July 27, 2011, 05:58:37 AM »

I have emailed & called a number of manufacturers of filters to see if we can get to the bottom of this. As of yet only a few have responded.

Quote from: Baldwin Filters

"RC,

BF940 has a 4 nominal with a 15 absolute micron rating.

Thank you,

Sandra H."

I also re-confirmed with Westerbeke tech support in Taunton, MA, 5 minutes ago, that the on engine 298854 is a 25 micron absolute rated filter. Joe J did not know what the nominal rating of the 298854 is...

Quote from: Donaldson Filtration

RC,

The P550127 filter that cross references to your Kubota filter has a 17 micron absolute and 5 micron nominal rating. This filter fits a large number of applications and may not match Kubota's micron specifications exactly. I don't know what the Kubota filters are specified to.

Thanks

It should be noted that Donaldson defines "absolute" as 99% of the particles trapped to 17 micron...
« Last Edit: July 27, 2011, 10:28:42 AM by mainesail »

Logged
-Maine Sail

Alan Gomes · Oct 23, 2023

Stu Jackson said:
Forget about the filter on the lift electric pump, it filters nothing unless it is the first in line from the tank in which case you get a very nasty surprise one day. It should be after the primary.

There are two schools of thought on primary / secondary filtration:

1. Primary should coarser, secondary finer - this is borne out by filter manufacturers, who should know , and everything we mechanical engineers learned in third grade.

2. Primary should be finer, secondary whatever it is, because the primary is almost always easier to access (the secondary is on the engine somewhere hard to get to). This is logical for a use case point of view.

The secondary on Universal engines is as John reported 10 microns, although I've read 25 to 30 in other fairly "researched" reports. I simply approach this as: it is what it is, 'cuz it's what fits on my engine and the equivalents from other filter manufacturers are the same rating.

I deliberately choose to have a finer primary on my boat because I CAN EASILY CHANGE IT.

And the reality is that because the filters we use are rated for much higher flow rates than any of our engines use, it really makes little difference.

I'd rather have my accessible filter clog first. Plus I can ignore changing my secondary for a long, long time.

I ran 2 micron primary for over 900 hours. I changed my secondary after 6 or 7 years. Engine still ran and still runs.

This is after 25 years of owning this boat and having seen and participated in more of these discussions than I could count.

Vacuum gauge for Racor fuel filter

Has anybody installed a vacuum gauge to indicate status of the standard Racor 225 fuel filter? If so, any tips (parts, where to locate the gauge, etc.) ?

forums.sailboatowners.com

Tally Ho · Oct 23, 2023

I think the OP just to know what the Racor part # is for the10 micron filter….

Greg