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Old 11-20-2015, 07:09 PM   #41
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When sensing insufficient fuel flow, I merely turn the lever 180 degrees to change filter.

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Old 11-21-2015, 11:46 AM   #42
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I can't imagine not having one. I transfer fuel back and forth between tanks through a 2 micron filter to make sure it is clean. With a new filter the gauge reads 2. I change it when it gets up to 10, does not happen very often. On the trip we just took I would open the hatch while underway and check the gauge. It never got over 3. Very reassuring to know when passing 20 or 30 barges a day in a narrow channel that your fuel supply is clean and flowing freely.
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Old 11-21-2015, 11:48 AM   #43
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Greetings,
Mr. R2G. "...that your fuel supply is clean and flowing freely." Same can be said about bowels...

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Old 11-21-2015, 01:14 PM   #44
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Unless your lift pump is located before the filter, it is atmospheric pressure that is forcing the fuel through the filters, even with top feed tanks and anti-siphon valves.

I have never seen a vacuum gauge calibrate for psi, although they could exist. There are other calibration units -- kPa and millibars -- and there are gauges that measure both vacuum and pressure. And there are gauges that measure absolute pressure (as if there were no atmospheric pressure) since atmospheric pressure varies slightly from day to day and one location to another.

Most people consider that they walk around under zero pressure, and the gauges most of us use make the same assumption. In fact, although it is a difficult concept to grasp, we are under under pressure from the atmosphere, and many of the phenomenon we experience every day are the result, like fuel going through our primary filters. If your boat were blasted into space, your lift pump would have to be replumbed before the primaries.
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Old 11-21-2015, 01:52 PM   #45
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@Doug. I don't think it is the absolute accuracy that is important here but the ability to 'see' the before and after differences in vacuum (however it is measured). As noted, all our boats idiosyncrasies have to be figured out individually. But being able to have a warning about fuel filter condition is very helpful to avoid embarrassing situations.
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Old 11-21-2015, 02:53 PM   #46
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Vacuum gauges are usually in mm of mercury (Hg). Pressure gauges can be calibrated to read "gauge pressure", pressure above atmospheric, or "absolute pressure", includes atmospheric pressure.
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Old 11-21-2015, 04:11 PM   #47
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My vacuum gage registers a vacuum as the filter element becomes dirty because the fuel pump has to draw the fuel thru the filter element. It's some thing I check regularly while underway along with the engine condition and shaft stuffing gland leak off. Seems to be a prudent procedure on a single engine trawler.
I'm very familiar with vacuum measured by a mercury column as was used on steam turbine driven Navy ships The column was scaled from 30" down to 20" with the other 20" of mercury in a reservoir.
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Old 11-21-2015, 05:19 PM   #48
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@Doug. I don't think it is the absolute accuracy that is important here but the ability to 'see' the before and after differences in vacuum (however it is measured). As noted, all our boats idiosyncrasies have to be figured out individually. But being able to have a warning about fuel filter condition is very helpful to avoid embarrassing situations.
You are absolutely right. I warned at the beginning that I was just being a PITA!
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Old 11-23-2015, 12:36 PM   #49
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I just bought a liquid filled on Amazon for under $10 , free freight.
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Old 11-23-2015, 12:45 PM   #50
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I should add that I am no expert on this. Others on this forum are more knowledgable.

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Not that I'm aware of (but I do know your skills sets a bit JD) unless you count the now banished RickB. Count me as another 30 micron primary guy.
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Old 11-23-2015, 10:15 PM   #51
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You are absolutely right. I warned at the beginning that I was just being a PITA!
If we were blasted off into space in our boats, there would be a lot more than just the gauges that would need to be recalibrated
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Old 11-23-2015, 10:19 PM   #52
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Not that I'm aware of (but I do know your skills sets a bit JD) unless you count the now banished RickB. Count me as another 30 micron primary guy.
Ditto
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Old 11-24-2015, 04:09 AM   #53
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Is there an electronic "read it on the bridge" version?
Maretron FPM100 module with a vacuum transducer PT-V-0-1BAR-01. Then it would be on a NMEA2000 bus.
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Old 11-24-2015, 06:23 AM   #54
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Unless your lift pump is located before the filter, it is atmospheric pressure that is forcing the fuel through the filters, even with top feed tanks and anti-siphon valves.
The lift pump pulls it thru the filter. "Lift" pump.
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Old 11-24-2015, 09:01 AM   #55
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Doug has it correctly, on all counts. The reference to vacuum "psi" was getting to me also but I let it pass. The reason youz guyz need vacuum gauges is because you have those junky Racor filters. Davcos are designed to show when the filter needs changed. Super simple, even a truck driver cant mess it up. And filters are WAY cheaper and more available.
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Old 11-24-2015, 10:35 AM   #56
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I can't tell you guys how many of those Racor vac gauges fail. I've replaced a bunch of them. Unscrew the thing and in your hand it reads 10"Hg. Great. Others read zero and you close off filter suction valve and the stupid thing still reads zero even as engine starts to starve.

Another one got an internal leak, air loaded the engine, then it stalled while the 90 footer was maneuvering in a current. He did hit with some damage. I redesigned his system so it had the gauges tee'd into the filter outlet line... with an isolation valve!! And got a commercial grade gauge.

If you guys want vac gauges, get something commercial quality, better yet, fluid filled. Not sure where Racor sources theirs, but the number of failures is off the chart.
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Old 11-24-2015, 11:49 AM   #57
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Never had any failures with the Racor brand, but I really like the Designated Engineer stuff.

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Davcos are designed to show when the filter needs changed. Super simple, even a truck driver cant mess it up.
I don't think the Davco's have the same water separation capacity the Racors or Fleetguards do, thus they are very rare on boats.
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Old 11-24-2015, 01:25 PM   #58
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Wrong. They have a better water seperation system and more water storage capacity. The have a provision for a water in fuel indicator switch, fuel heater (electrical or engine coolant), and they dont pretend to be "turbine centrifugal" or anything stupid like that. Just good dependable filter units that are used on lots of commercial boats.
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Old 11-24-2015, 01:48 PM   #59
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Wrong. They have a better water seperation system and more water storage capacity. The have a provision for a water in fuel indicator switch, fuel heater (electrical or engine coolant), and they dont pretend to be "turbine centrifugal" or anything stupid like that. Just good dependable filter units that are used on lots of commercial boats.
Interesting, I thought they got out of the marine market when they discontinued the SeaPro line. They don't seem to have "marine" listed as an application for any of their current filter systems, not that you couldn't use one.
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Old 11-24-2015, 01:53 PM   #60
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Greetings,
Re: Post #44...(from and off site friend-read expert)

Unless your lift pump is located before the filter, it is atmospheric pressure that is forcing the fuel through the filters, even with top feed tanks and anti-siphon valves."

Not necessarily. As long as the fuel level is above the pump and/or filter the the suction head is positive and fuel will flow through the filter without the pump. Even in a vacuum ... as is amply demonstrated by the ancient technology used to remove dead steam (condensate) from the bottom (hotwell) of the condenser of a steam plant, which normally operates at a vacuum of around 28 to 29"HG which is pretty darned high vacuum. It works because you always keep a couple feet of water above the pump impeller level.
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