Fuel Filter Replacement

Jun 7, 2016
312
Catalina C30 Warwick, RI
Another thread about fuel tanks has me thinking about my fuel filters. I have a Racor filter/water separator as my primary and the engine mounted fuel filter as my secondary. The Racor has a vacuum gauge with a drag needle so I can see if it is getting restricted. If there is no water in the bowl and my drag needle has not moved off of 0, is there any reason to replace the filters after X amount of time or hours?

My thought would be no, being that if there is no restriction / vacuum in the primary then I should be good, but I just wanted to make sure I wasn't missing something.
 
Sep 25, 2008
6,316
Alden 50 Sarasota, Florida
It’s not expensive to replace a filter annually but to answer your question by example, if there was a hole in the filter fabric making it useless, the vacuum gauge would read exactly what you describe. Likely no but possible?
the moral of that example is - your choice.
 
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Jun 7, 2016
312
Catalina C30 Warwick, RI
I have always been of the annual filter replacement mindset, but that was on my old boat with no primary filter or vacuum gauge. Never knew if I was "over replacing" them.
 
Feb 10, 2004
3,510
Hunter 40.5 Warwick, RI
I have vacuum gauges on both of my primary filters for the auxiliary and the genset. Neigther seem to move off zero either, or at least very little. So I replace the primary about every 4-6 years mostly from a guilty feeling.
I put 130-150 hours each year on both of the engines.
At $30-35 for each Racor filter, I don't see the point of just replacing yearly. I'm happy to replace if needed, but otherwise I continue using. Maybe I never get a batch of dirty fuel?
 

NYSail

.
Jan 6, 2006
2,742
Beneteau 423 Mt. Sinai, NY
I have a racor 500 as a primary. I check the filter a couple of times during season…….. replace every other year unless I was to notice water/ debris. So far in past 15 years with two separate boats every other year it has been. And when I change primary I do the secondary as well. have 2 spares on hand of each filter always.

good luck
Greg
 
Jan 4, 2006
3,912
Hunter 310 West Vancouver, B.C.
So I replace the primary about every 4-6 years mostly from a guilty feeling.
Exactly the route I've gone after religiously replacing them annually after the first couple of years.

I did tear apart a several year old used filter and found it to be every bit as robust as a new filter so why bother ? Another reason for not bothering is that we have good fuel in this area. I just keep my finger crossed up north.

Someone here once made the statement that fuel filters absorb water hence you should replace them frequently. I put this idea to someone at a major filter dealer here in Vancouver and walked away feeling like an idiot for posing such a dumb question.

Lesson learned: Be careful not to repeat what you may have read on a forum unless you know exactly what you're talking about.
 
Feb 26, 2004
21,959
Catalina 34 224 Maple Bay, BC, Canada
Rich & Ralph are right. My last filter was replaced after 900 hours. How come my engine kept running?
 
Dec 14, 2003
1,320
Hunter 34 Lake of Two Mountains, QC, Can
I'm also of the opinion that if your fuel is clean there is no need to replace the filter annually. But in order to rest my mind a few years back I did install a vacuum gauge. Not to hijack this thread but I do have a question pertinent to that vacuum gauge ? Needle never ever moved anywhere from zero since installed but 2 years ago I did have a fuel starvation problem with the needle still at zero. So I wonder why the needle had never moved to point to the starvation issue ? The gauge is teed on the fuel line in-between the Racor and the fuel pump. When it happened (to make matters worse it was in the middle of the shipping lanes on the lower St.Lawrence River), I replaced the Racor filter, cleaned the fuel and it's been running without a problem since. Been a couple of years and coming up on 200 hours in ! Until I can figure out why that gauge is not working, I know after close to 200 hours I should perhaps change the Racor filter as it is fairly cheap insurance. Ideas anyone ?
 
Jun 15, 2012
628
Hunter 50 AC St. Petersburg
I'll bet that unless your fuel supply gets contaminated with algae, it will be good for 10+ years. I have owned my boat almost 6 years, and even after 2 trips by engine from NY to FL I have not changed the filter. The engine runs perfectly. I do however keep 2 spare filters on board.
 
Jan 4, 2006
3,912
Hunter 310 West Vancouver, B.C.
I got two nickels and a ball of lint in my right rear pocket that says the gauge is at fault. I know that after I first installed my vacuum gauge, I just HAD to close the fuel supply line to see what happened. The engine was idling and the vacuum slowly increased to about -15" Hg before the engine started to slow down. Every few years I'll test the gauge to see if it's still in working order. I have an isolation valve in front of the gauge and always leave it closed. The bourdon tubes in those gauges are paper thin and I don't need an unexpected leak under the aft bunk.

DSC_0511_Fotor.jpg

Just a thought, but back in the day we never used vacuum gauges ONLY. They were always compound gauges as shown above. If the gauge is in a location where a positive pressure can be generated (usually as a result of temperature increase when shut down) and something acts as a check valve, the gauge can be damaged by being driven in the opposite direction.
 
May 7, 2012
969
Hunter e33 Maple Bay, BC
I have a Racor filter/water separator as my primary and the engine mounted fuel filter as my secondary. The Racor has a vacuum gauge with a drag needle so I can see if it is getting restricted. If there is no water in the bowl and my drag needle has not moved off of 0, is there any reason to replace the filters after X amount of time or hours?
No . . . but as suggested, you should close the fuel line valve while the engine is running to confirm the vacuum gauge is working. When I installed my Racor vacuum gauge with drag needle 4 years ago, I posed this question to Racor Tech support with their response following:

How do I know when it's time to change my Racor fuel filter if I have an RK19671 fitted?

Ideally, you use a vacuum gauge to monitor filter restriction, and change your filter when the gauge reads 5 to 8 inHg above the starting vacuum (about 7 to 10 inHg is typical). This insures that your filter is still removing water at high efficiency. You can change out at higher vacuum, but water removal efficiency will be impacted as the vacuum goes up. If no gauge is installed, filters should be changed at least once a year, or at the first sign of engine power loss.
 
Jan 4, 2006
3,912
Hunter 310 West Vancouver, B.C.
This insures that your filter is still removing water at high efficiency. You can change out at higher vacuum, but water removal efficiency will be impacted as the vacuum goes up.
Any thoughts on how vacuum impacts water removal ? No chance of the water vaporizing at 10" Hg (temp. around 190 deg. F.) so what changes ?
 
May 7, 2012
969
Hunter e33 Maple Bay, BC
Any thoughts on how vacuum impacts water removal ? No chance of the water vaporizing at 10" Hg (temp. around 190 deg. F.) so what changes ?
Ralph chemistry is not my strong suit. But from what I read in the link below “At 15 inches of vacuum, diesel fuel will boil.”. So assuming that is accurate and given that the boiling point of diesel fuel ranges between 150 to 380 deg C, just maybe the temperature is actually higher than the boiling point of water??? Thinwater HELP!

Racor Mythbusters: Fuel Filters
 

dmax

.
Jul 29, 2018
503
O'Day 35 Buzzards Bay
The boiling point of a liquid is dependent on the atmosperic pressure around it - at 30 Hg of vacuum, water will boil at less than 70 degrees Farenheit. The 150 - 380 C range for diesel boiling assumes sea-level air pressure.
 
Oct 2, 2008
3,589
Pearson/ 530 Strafford, NH
I'll bet that unless your fuel supply gets contaminated with algae, it will be good for 10+ years. I have owned my boat almost 6 years, and even after 2 trips by engine from NY to FL I have not changed the filter. The engine runs perfectly. I do however keep 2 spare filters on board.
My racor 500 has replacement filters for less than $15 so if I see any accumulation in the bowl, it gets replaced regardless of the drag needle.
 
Jul 5, 2011
598
Oday 28 Madison, CT
I have vacuum gauges on both of my primary filters for the auxiliary and the genset. Neigther seem to move off zero either, or at least very little. So I replace the primary about every 4-6 years mostly from a guilty feeling.
I put 130-150 hours each year on both of the engines.
At $30-35 for each Racor filter, I don't see the point of just replacing yearly. I'm happy to replace if needed, but otherwise I continue using. Maybe I never get a batch of dirty fuel?
I am with Rich. Fine screen in the lift pump get cleaned annually and the engine's fuel filter also. The Racor is nice insurance but no need to "renew the policy" yearly if you are getting clean fuel in my view. My usage is light, 10-20 engine runs a year or so. (I do have a spare ready to go just in case.)