diesel fuel filters


New member
BC Canada
Can someone help me? I'm new to diesel motors and trying to learn what all the bits and pieces on mine are and how they work.

This (attached image: Baldwin BF791) is the primary fuel filter for our Yanmar 3YM30. Diesel flows from it to the tank to the motor. There's another smaller version of it on the motor itself. I feel that I should have a Racor style spin on filter with a clear bowl? Should I replace the Baldwin filter with a Racor one? Should I add a Racor filter closer to the fuel tank and keep the Baldwin one too? What's best practice here?



Son of Hans

San Diego
I hope for your sake you meant that fuel flows from the tank to the filter to the engine!  What you have here is purely a fuel filter.  The devices with clear bowls are also water separators.  Whether you need that or not is an open question.  I have never found any water in mine, but YMMV.  Be aware that if you install one with a clear (plastic) bowl in the engine compartment, ABYC regulations (by some interpretations) and some insurance companies demand that it be equipped with a fire shield, although we all know that's not particularly important for diesel.  There's a thread or two on that.



Overlord of Anarchy
San Diego
^^^ Wot he said. Nothing inherently wrong with what you've got, but a Racor type filter will also remove water from the fuel. Also the larger bits of crud will stay in the clear bowl giving you a better glimse into your fuel health. The fire sheild is a ss bowl mounting under the plastic bowl. Just takes a bit more room to install.

And on another front, that cockpit drain fitting is nylon - those gradually weaken from UV exposure. At some point, they will break off quite easily.



Super Anarchist
Unless you've got a contaminated tank (water and/or diesel bugs) or are running your engine for hundreds of hours per year, this should be plenty adequate. The Baldwin is a 9 micron filter, which is what you want for that Yanmar. Change both filters every year, add a dose of Biobor with each fill, keep your tanks full in the off season, and make sure you've got a decent o-ring on your deck fill to keep liquid water out and you should be fine. 



Super Anarchist
I have picked up water (in quantity like 0.5-1 L) a few times. First boat had a big opaque filter housing with an inside cartridge. Second had a Racor 500. Both were good at water separating while this type is not. But... you'll probably be fine.

If you do replace it with a water separating one you can just sell this one. No need for two primary + engine mounted filter.


The Q

Super Anarchist
Built My own diesel polisher, whenever I'm working on the boat I stick the inlet and outlets into the fuel tank and leave it running..

it goes.

Inlet, long copper pipe into tank

rubber to glass demijohn,

copper pipe through bung to bottom of demijohn,

copper pipe  from 3/4 way up demijohn through bung

to pump, 

to filter,

to rubber pipe back into tank.

The Demi john allows water and gunge to settle out, reducing filter changes and you can easily see what's happening..

Doesn't need a huge pump as I'm not in a hurry, the copper pipe reaching the bottom, draws off water  and gunge from the  tank..

First time a couple of gallons of water were drawn out, since then, not a lot...

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Turgid Member
Always have at least one spare filter on board. In rough weather it is not uncommon for gunk in the bottom of the tank to go into suspension and plug the filter. Have a cut-away milk jug to catch any drips.

The see through bowls are nice if you are in the habit of checking them often. I caught water in a tank with one before it became a problem.



Super Anarchist
Land of the locks
One small advantage of a Racor bowl type filter is the stopcock at the bottom. If some gunk or water settles out and you are in a diffcult situation you can drain the bad stuff and keep going for a while before changing out the filter. This implies you are checking it pretty often, which I never do.

It also makes filter changes cleaner by draining the fuel from the filter before removing it. It is hard to get the one piece ones off without slopping some fuel.



Super Anarchist
Great Wet North
I regard a Racor as an essential piece of gear - I had canister filters on one boat and hated them - you can't tell what's going on.

My current setup has the Racor, the water strainer and the seacocks all in one place so everything gets checked every time I open or close the seacocks - basically twice every time the boat goes out - I really like it.

Engine 5.JPG



Super Anarchist
I have a filter question, too!

One of my Racor 225R filters has gone bad -- a combination of fuel gunk and decay. I don't think rebuilding it makes sense. It looks like the 225R is no longer easily available (or my google-fu is poor). The filter is for a yanmar 2gm20. It looks like the 230R is a plug in replacement plumbing wise but it takes different filters and has a lower flow rate. I have a small fortune of R26S filters. I have two engines with the same setup.

As I've been contorted in the engine room huffing diesel fumes I'm thinking I may not be thinking very well (even by my usual modest standard). Options that come to mind:

Find a 225R replacement but that looks to be hard and/or expensive.

Replace the bad filter with a 230R and deal with two different filter types aboard.

Replace both and donate my cache of R26S's to a good cause.




Super Anarchist
I've taken apart a few Racor's to clean out. They are quite simple. I'd go the re-build route.
Thanks. That was my first thought, too. However, there is some deterioration of the casting and the primer pump parts all need replacing. Parts and labor considered I think it's time to replace it.



Super Anarchist
^^^ that is an immaculate engine space. 

I just dug the ~~tar~~ out of my 225.  Apparently my fuel tank is not immaculate. I need to do some serous fuel polishing and tank cleaning.


Rain Man

Super Anarchist
Wet coast.
If you are making changes, and time and money is no object, consider putting a two stage Racor system in.  The big advantage of this is that you almost never need to change the filter on the engine, since the two-stage will remove virtually all the gunk before it can get to the engine filter.   If you don't need to change the engine filter you will probably not have to bleed the system after a filter change provided you keep a small quantity of fresh diesel on board to fill the Racor up with.  So, the scenario where you are at sea and the filter clogs requiring a change becomes less of a nuisance.

We have a two-stage filter and, since they hadn't been changed since we bought the boat in 2020, changed all the filters a few weeks ago.  The two filters in the Racors were a bit ugly, but the one on the engine was pristine - we could have left it but changed it anyway.  

One of the PO's also put in an electric fuel pump switchable to the outlet of the Racors and plumbed in a return to the fuel tank, creating a fuel polishing system.  We can run the entire tank of fuel through the filters if we want - also eliminating any air bubbles left after a filter change.   It also means we don't have to carry fresh diesel for filling up the filter after a change because the pump is strong enough to pull fuel up out of the tank to fill the filters. 

We thank our PO, where-ever he/she is, for doing that.  There is some other stuff they could have fixed though.

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