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Old 03-23-2020, 07:24 PM
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Polishing filter upstream of mechanical fuel pump?

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?
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Old 03-23-2020, 09:49 PM
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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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Old 03-24-2020, 09:32 AM
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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!
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Old 03-25-2020, 09:25 AM
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Quote:
Originally Posted by Surcouf View Post
...the more pressure loss at the suction, the higher the chance to get air ingress...
Interesting, thanks! I'll have to take a look at the pressure drop across that filter.

Quote:
Originally Posted by Surcouf View Post
I go by a simple rule: I do whatever Don Moyer recommends!
Yeah, I may end up just doing the standard installation right at the carb. It's certainly doable. I just like the idea of better access to the filter and connections out by the other filter.
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Old 03-25-2020, 11:36 AM
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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??
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Old 03-25-2020, 09:09 PM
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Originally Posted by joe_db View Post
Pressure side filters like putting a RACOR after the fuel pump are not legal for boats or at least won't pass ABYC.
I'm not sure I understand what you're telling me. I have a bronze Perko before the fuel pump, and I bought a polishing filter that's recommended to put after the pump. But I'm considering putting the polishing filter before the pump for ease of access.
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Old 03-25-2020, 09:34 PM
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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).
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Old 03-25-2020, 10:17 PM
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What do you think the inline filter will do for you?
Good point. I guess I want to make sure I get everything the primary filter missed, mostly to maximize engine reliability. The primary is an old Perko and the element looks like a sea sponge (slight exaggeration) so I can't imagine it's better than 20-30 microns.
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Old 03-25-2020, 10:37 PM
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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.
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Old 03-26-2020, 09:35 AM
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Quote:
Originally Posted by ndutton View Post
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.
This is all part of a general fuel system overhaul because my A4 got harder and harder to start at the end of the season (I've been through numerous other threads on that topic so that's not my intention here). Anyway, I rebuilt my fuel pump and carb as part of a potential fix, and figured I'd go ahead and address the filters while I'm at it. I intend to replace the Perko with a newer Racor or similar at some point, but probably not now just for budgetary reasons.

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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Old 03-26-2020, 09:52 AM
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Quote:
Originally Posted by scratchee View Post
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.
That's not my experience with ethanol blended fuel at all. I have run a steady diet of E10 for 15 years with no chalky white residue. I suspect you have ingested water in the system that made it to the carburetor and remained there for some time. What you have described could explain your hard start problems. Whenever the budget allows, a higher grade, better condition water separating main filter may solve everything.

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).

edit:
If there is water in the system, where did it come from? That is the real problem, not how to manage it.
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Last edited by ndutton; 03-26-2020 at 09:55 AM.
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Old 03-26-2020, 10:22 AM
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Originally Posted by ndutton View Post
If there is water in the system, where did it come from? That is the real problem, not how to manage it.
I'm thinking along the same lines. The Perko does have a water separator, and I didn't see any standing water in it when I drained it for this project. But I have read that E10 absorbs water, even from humid air (I'm in very humid Maryland), and I thought this could be the source of the chalky buildup which in turn could have clogged passages in the carb. So I'm hoping a fuel system overhaul, potentially including a new tank (I have to measure to see if it requires cutting up the cockpit!), might at least remove the fuel as a source of uncertainty.

I really appreciate the help by the way!
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Old 03-26-2020, 09:14 PM
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Did you find this thread from three years ago?
http://www.moyermarineforum.com/foru...d.php?p=103779
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Old 03-27-2020, 08:56 PM
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Did you find this thread from three years ago?
http://www.moyermarineforum.com/foru...d.php?p=103779
Actually, I hadn't seen that. Thanks a bunch! Very informative.

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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Old 03-27-2020, 11:56 PM
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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 ˝ teaspoon in a 20 gallon tank, worst case. You probably get more than that from the swill pumped in at the fuel dock.


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Originally Posted by scratchee View Post
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.
This sounds like a much more logical source of water (how often do you replace the fill plate O-ring?) in the fuel. There's another thread about that. The O-ring is mentioned in post #1, water separating filter discussion starts at post #7.
http://www.moyermarineforum.com/foru...ad.php?t=11084
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Old 03-28-2020, 12:30 AM
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"Replace the o-ring?"
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Old 03-28-2020, 12:07 PM
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That's the o-ring on the filler cap!

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Old 03-28-2020, 01:46 PM
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My water issue was solved with a new O ring
Note that ethanol corrodes the metals in our cabs and water, even water you can't see in suspension with the ethanol, makes it much worse. I got ahead of this issue by getting a new carb, a new O-ring, and adding SeaFoam to the gas every fill. SeaFoam is cheap and has decent anti-corrosive properties. I think once the carb gets eaten into beyond a certain point, it will keep corroding. It may not be there yet for you, but the water HAS to be kept out from now on. I actually have heard good things about those old Perko filters, they are easy to drain and easy to clean. The Moyer polisher will catch anything that gets past it.

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Old 03-28-2020, 09:29 PM
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Yeah, I've kept an eye on the o-ring on my filler cap. I've always been a little nervous about the filling port being essentially on the bottom of a bathtub if my cockpit drains get clogged (most likely with leaves while on the hard). The o-ring seems to be in good shape, but I've never replaced it.

When I think about water in the fuel, I assume there are two dangers: fuel that won't burn, and/or corrosion that puts sediment in the fuel stream. I think my problem, if indeed it is caused by water, is the latter. My symptoms are the engine not starting after it has sat for several days. It will crank and crank and crank, and when the battery is about dead it will finally fire weakly for a turn or two. If I'm lucky enough to get it started before the battery goes dead, I can nurse the throttle and choke for a couple minutes until she's warm. After that, it runs fine for as long as I need. So if I had actual water in my fuel line, I would think there would be enough good fuel in the carb and pump to get me started the next time.
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Old 03-29-2020, 10:08 AM
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Quote:
Originally Posted by joe_db View Post
My water issue was solved with a new O ring....
What issues were you having?

Quote:
Originally Posted by joe_db View Post
Note that ethanol corrodes the metals in our cabs and water, even water you can't see in suspension with the ethanol, makes it much worse.
Thanks, this addresses my original question, because I figure that if the carb is effected the mechanical pump probably is too. Last week I removed the sediment bowl in the newly-overhauled pump, and it was already covered with a fine powdery coat. Nothing that would interfere with the engine, I don't think, but certainly an indication that something is getting added to the fuel. So putting the polishing filter after the pump is probably what I'll do. And I'm going to look at discarding the existing fuel in the tank, as well as a possible tank replacement, or at least an internal inspection. I have a cheapy inspection camera that I may be able to use without blowing myself up.
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Old 03-29-2020, 11:18 AM
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Quote:
Originally Posted by scratchee View Post
The o-ring seems to be in good shape, but I've never replaced it.
How long have you owned your boat?
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Old 03-29-2020, 11:34 AM
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Exclamation Residue

If you are getting residue in the freshly rebuilt carb and pump you have bad fuel. The powdery stuff you see is from condensation attacking the body of the carb. No amount of filters will filter it out as it is emulsified into the fuel as a liquid. This liquid flows through the filters freely and shows once the fuel begins to evaporate.
I see a few things in your posts that need clarification.

Hard to start can also be from a weak battery not spinning the beastie fast enough. Have the battery tested and check the connections.

The choke may not be all the way closed check it visually. OR a vacuum leak at the carb base.

Have you checked for a good spark?

Did you prime the carb with the bail on the pump?

Next thing is fuel. This is a lot of fuss for something so easily checked out. Get a small gas can with fresh regular grade gas and hook it to the carb and gravity feed or to the pump and let it feed the carb. If it starts and runs don't use the fuel in the boats tank!!!

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Old 03-29-2020, 11:46 AM
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Original 1977 FRAM gas/water separator

I've had one of these on my Pearson since new. It is steel and aluminum cap. It has been dependable. I have never had a problem with water in fuel or phase separation. It would take a lot of water to saturate today's 10% ethanol fuel- remember "Dry Gas" was simply a dose of ethanol alcohol to absorb water in fuel system to prevent icing. The Pearson has a MONEL tank which is a real premium material for gasoline tanks. My inlet is also in the cockpit sole and has the original chrome plated bronze inlet. I do not use an O-Ring but I keep the threads in the cap heavily greased. Standing water for days or weeks over the gas inlet may overcome any effort to keep the gasoline 'dry'.
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Old 03-29-2020, 12:24 PM
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Exclamation Filter water separaator

Fuel/water separators work very well at letting the "WATER SETTLE" to the bottom of the filter for extraction/storage. They are for filtering particulate matter down to there micron rating and do a very good job. They will not filter out "emulsified water or goo" as they just pass on through. It is bad fuel and then it gets to the fuel system and in the carb. When the fuel evaporates away the emulsified water or goo precipitates out to deposit and cause havoc to the carb body and orifices.

No matter how many filters you add bad fuel is bad fuel and the "bad" won't filter out unless it is a particulate!

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Old 03-29-2020, 09:06 PM
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Quote:
Originally Posted by Dave Neptune View Post
Next thing is fuel. This is a lot of fuss for something so easily checked out.
No worries Dave, the carb and fuel pump rebuilds were due just on general principle, and they were fun winter projects. How else would I have ended up with this beauty hidden behind the lower drawer in my saloon?



The two barbs are where I'll be putting that polishing filter.

Your other helpful tips I've either already done or have reason to believe they're not an issue at the moment (battery, spark, etc). I do expect to discard the fuel in the tank. Thanks!
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