I've just reinstalled my mechanical fuel pump and carb after a rebuild. I have the polishing filter kit from Moyer (a new addition to my fuel system), and in looking at the installation location, I'm wondering if it would really be a problem to put that filter right next to my primary filter a few feet away. I know that ideally I'd want it immediately before the carb, but if I put it next to the other filter the only thing I'm adding to the post-filter path is a few feet of hose and the mechanical fuel pump. And I'm thinking that if the mechanical fuel pump is putting debris into the fuel line then I'm probably not going to be running much longer anyway. The advantage, on the other hand, would be fewer fuel connections (and a shorter and more direct path) in a less accessible area right next to the engine. Has anyone done something like this?
Polishing filter upstream of mechanical fuel pump?
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Another consideration.. I had a polish filter right before the carb that was sending its own corrosion products to the carb! Filter was of steel construction, and corroded internally due to moisture in the fuel. I lost a lot of sailing time one summer tracking that one down.
If you install one, check it with a magnet. I think an aluminum one is good to have - catch the corrosion products from the main filter. DO NOT use a plastic one - fire hazard.
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back to my design engineering days... it is "harder" for a pumping system to have pressure loss at the suction that at the discharge. I think it is called friction loss.
Moreover the more pressure loss at the suction, the higher the chance to get air ingress, as you increase your negative pressure at the pump suction.
but this is just engineering... reality is different, and I go by a simple rule: I do whatever Don Moyer recommends!Surcouf
A nostalgic PO - Previously "Almost There" - Catalina 27 (1979)
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Originally posted by Surcouf View Post...the more pressure loss at the suction, the higher the chance to get air ingress...
Originally posted by Surcouf View PostI go by a simple rule: I do whatever Don Moyer recommends!
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Pressure side filters like putting a RACOR after the fuel pump are not legal for boats or at least won't pass ABYC. Besides for that, if you get a load of crap in your fuel do you want to be changing elements or fuel pumps?
The Moyer filter is "sort of" OK because it doesn't come apart or unscrew. Speaking of, mine has been on for ages and ages. I need a new filter, not a whole new kit. Where is the listing for just the filter??Joe Della Barba
Coquina
C&C 35 MK I
Maryland USA
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Originally posted by joe_db View PostPressure side filters like putting a RACOR after the fuel pump are not legal for boats or at least won't pass ABYC.
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What do you think the inline filter will do for you? The answer to that may determine where in the fuel path it belongs. MMI lists their inline filter as 7-10 micron, MMI's Racor filter is 10 micron, if using something other than the Racor, most of them are 10 micron too (the Sierra 18-7945 for example).Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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Originally posted by ndutton View PostWhat do you think the inline filter will do for you?
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Okay, it sounds to me like the primary filter needs a lot more attention (replacement/upgrade?) than placement of the polishing filter.
Consider this:
If you place the polishing filter where you're suggesting you'll have no filtration after the filters, through the pump and all the way to the carb. With the polishing filter in the MMI position it is the last line of defense before the carb. I'm thinking you might be giving up the intended benefit of the polisher.Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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Originally posted by ndutton View PostOkay, it sounds to me like the primary filter needs a lot more attention (replacement/upgrade?) than placement of the polishing filter.
Consider this:
If you place the polishing filter where you're suggesting you'll have no filtration after the filters, through the pump and all the way to the carb. With the polishing filter in the MMI position it is the last line of defense before the carb. I'm thinking you might be giving up the intended benefit of the polisher.
By the way, while working on the carb I discovered a) a bunch of the chalky stuff that I assume is related to ethanol, and b) the two halves didn't mate well, so I machined them for a better fit.
In the next few days I should have everything back together and I'm sure it'll fire right up!
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Originally posted by scratchee View PostBy the way, while working on the carb I discovered a) a bunch of the chalky stuff that I assume is related to ethanol, and b) the two halves didn't mate well, so I machined them for a better fit.
Any reaction to the discussion about the position of the polishing filter? That is really what you asked about before I deflected to the main filter (and continue to do so).
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If there is water in the system, where did it come from? That is the real problem, not how to manage it.Last edited by ndutton; 03-26-2020, 09:55 AM.Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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Originally posted by ndutton View PostIf there is water in the system, where did it come from? That is the real problem, not how to manage it.
I really appreciate the help by the way!
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Did you find this thread from three years ago?
Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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Originally posted by ndutton View PostDid you find this thread from three years ago?
http://www.moyermarineforum.com/foru...d.php?p=103779
My filler cap is on the cockpit sole, and it has gotten flooded with rain a couple times when the drains clogged. I've never seen any water in the separator but it's quite possible that water did get into the tank.
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The purpose of the math exercise in that old thread was to calculate for ourselves the real world insignificance of assumed water contribution to the fuel stored in a vented tank of typical volume due to atmospheric humidity. Without the word salad, it's less than ½ teaspoon in a 20 gallon tank, worst case. You probably get more than that from the swill pumped in at the fuel dock.
Originally posted by scratchee View PostMy filler cap is on the cockpit sole, and it has gotten flooded with rain a couple times when the drains clogged. I've never seen any water in the separator but it's quite possible that water did get into the tank.
Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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