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Old 08-17-2016, 07:28 AM   #21
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And plus 1 for plastic strainers.
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Old 08-17-2016, 07:47 AM   #22
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Ted, I believe the failure of the stainless baskets with plastic bottoms (maybe other than plastic also) might be from (help me Boatpoker if I use the wrong terminology) crevice corrosion. The bottom of the strainers usually have some junk in them after awhile and the stainless just loses its protective barrier. Maybe also from the plastic interlock.


18-8 Stainless steel, 304, 316 Stainless Steel Corrosion


2. Crevice Corrosion - this is a problem with stainless fasteners used in seawater applications, because of the low PH of salt water. Chlorides pit the passivated surface, where the low PH saltwater attacks the exposed metal. Lacking the oxygen to re-passivate, corrosion continues. As is signified by its name, this corrosion is most common in oxygen restricted crevices, such as under a bolt head.
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Old 08-17-2016, 08:15 AM   #23
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I have a stainless rudder on my charter boat. Without a zinc, it pits and deteriorates. With a zinc, there is no noticeable pitting or corrosion. What is the process that causes this deterioration and how is it any different than what happened to the strainer basket?

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Old 08-17-2016, 08:27 AM   #24
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When an "expert" uses the term "electrolysis" I know that marine corrosion is not their field of expertise. In my tenure with ABYC I helped develop the ABYC Marine Technician Corrosion course. In boats, the corrosion we most often deal with is galvanic corrosion. An application of sacrificial anodes is usually involved. We sometimes see stray current corrosion, but not very often. With stainless steel in salt water we sometimes see crevice corrosion. Adding anodes will not make any difference if crevice corrosion is the issue. As one who has SS sea strainer baskets, I see the corrosion start at the welds. This is a good indication that the issue is indeed crevice corrosion. Our boat was built in China in 2008 and some of the sea strainers are US products and some are Chinese. I have fewer problems with the baskets from Buck Algonquin, and can order replacements. I cannot seem to find replacement baskets for the Chinese knock off sea strainers.
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Old 08-17-2016, 08:57 AM   #25
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When an "expert" uses the term "electrolysis" I know that marine corrosion is not their field of expertise. In my tenure with ABYC I helped develop the ABYC Marine Technician Corrosion course. In boats, the corrosion we most often deal with is galvanic corrosion. An application of sacrificial anodes is usually involved. We sometimes see stray current corrosion, but not very often. With stainless steel in salt water we sometimes see crevice corrosion. Adding anodes will not make any difference if crevice corrosion is the issue. As one who has SS sea strainer baskets, I see the corrosion start at the welds. This is a good indication that the issue is indeed crevice corrosion. Our boat was built in China in 2008 and some of the sea strainers are US products and some are Chinese. I have fewer problems with the baskets from Buck Algonquin, and can order replacements. I cannot seem to find replacement baskets for the Chinese knock off sea strainers.
Since this deterioration isn't at or near a weld (plastic bottoms on the basket), are you thinking it's more likely galvanic corrosion?

Don't know if that "expert" swipe was directed at me; am not one and never claimed to be one.

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Old 08-17-2016, 09:12 AM   #26
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My comment was not directed at anyone here. I interact with the cruising/boating/boatyard community in many ways and many levels. The professionals I wor with in the field of marine corrosion do not use the term electrolysis
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Old 08-17-2016, 11:08 AM   #27
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We will be replacing our original raw water strainers with these marelon units from Forespar:

https://youtu.be/00xpK1C9ktY
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Old 08-17-2016, 11:14 AM   #28
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We will be replacing our original raw water strainers with these marelon units from Forespar:

https://youtu.be/00xpK1C9ktY
I used them and hate them because they clog easy.

Everything else is nice, but the tripod top holder allows fairly small objects to clog them....and then they are a bitc* to clean out.

Yes, outside the hull thru hull covers may prevent that, but I prefer an open thru hull for excellent reasons and other strainers wouldn't clog like the Forespars.

If I was in the market again, I would look closely at the Raritan strainers.
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Old 08-17-2016, 11:41 AM   #29
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We will be replacing our original raw water strainers with these marelon units from Forespar:

https://youtu.be/00xpK1C9ktY
My generator had one of those when I bought the boat. Lid was cracked from the retainer hole out to the edge. Be careful not to over tighten the retaining nut.

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Old 08-17-2016, 02:14 PM   #30
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Never use a plastic strainer basket! They last way too long and I can't get rich selling replacement baskets! Seriously, the plastic does seem to last longer. The holes are usually a little bigger but I've never heard of anyone having a problem because of that.



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Old 08-17-2016, 02:25 PM   #31
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I used them and hate them because they clog easy.

Everything else is nice, but the tripod top holder allows fairly small objects to clog them....and then they are a bitc* to clean out.

Yes, outside the hull thru hull covers may prevent that, but I prefer an open thru hull for excellent reasons and other strainers wouldn't clog like the Forespars.

If I was in the market again, I would look closely at the Raritan strainers.

If it's not a Groco, I won't go.
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Old 08-17-2016, 03:43 PM   #32
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I rolled my own plastic strainers using a plastic mesh canvas, similar to this.
Darice® Stiff Canvas Mesh, Clear

All I recall was it was white mesh my wife had some and said she got from the craft store.

If it is too stiff to bend tight, I used a heat gun to soften into a roll. Then I used copper wire to secure the ends like a stitch thru the holes. Monofilament I could have used instead.

I did this many years ago and it has never failed. It cost me nothing but time.
It works, I mean it passes the water just fine.And I suppose strains out stuff. Our water does not have much trouble regarding the need for strainers. Nothing stops jellyfish from clogging the line.

When I pull them out every so often to see, they look just like when I made them. These are fit into 2 Sendure Y strainers.

I have a Perko bronze strainer with SS basket. It must be decades old. The SS basket is in fine shape, who knows, maybe it is Monel. The Perko strainer has a clear plastic tube maybe 4 inches across and thick outer part that is crazed. Where do you get new ones?

The pipe size for it is 1/2 inch.
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Old 08-17-2016, 11:42 PM   #33
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I rolled my own plastic strainers using a plastic mesh canvas, similar to this.
Darice® Stiff Canvas Mesh, Clear

All I recall was it was white mesh my wife had some and said she got from the craft store.

If it is too stiff to bend tight, I used a heat gun to soften into a roll. Then I used copper wire to secure the ends like a stitch thru the holes. Monofilament I could have used instead.

I did this many years ago and it has never failed. It cost me nothing but time.
It works, I mean it passes the water just fine.And I suppose strains out stuff. Our water does not have much trouble regarding the need for strainers. Nothing stops jellyfish from clogging the line.

When I pull them out every so often to see, they look just like when I made them. These are fit into 2 Sendure Y strainers.

I have a Perko bronze strainer with SS basket. It must be decades old. The SS basket is in fine shape, who knows, maybe it is Monel. The Perko strainer has a clear plastic tube maybe 4 inches across and thick outer part that is crazed. Where do you get new ones?

The pipe size for it is 1/2 inch.
Does your Perko strainer have a single large wing nut on top or two small ones that hold the lid on? I'll see if I can find the part number for you.

If your basket is old enough, it might be Monel. Groco still offers Monel baskets, I don't think Perko does.
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Old 08-18-2016, 11:26 AM   #34
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Does your Perko strainer have a single large wing nut on top or two small ones that hold the lid on? I'll see if I can find the part number for you.

If your basket is old enough, it might be Monel. Groco still offers Monel baskets, I don't think Perko does.
It has a single large acorn nut that holds on the top cover plate. Cover plate is 1/4 thick bronze smooth with no ridges, like a large thick washer.
Strainer is from 1970.
I think it is a Groco since all the Perko have 2 bolts holding the top cover?
It is plumbed with 1/2 inch NPT. It was installed with the Onan generator decades ago.
The basket I recall gets a greenish tinge, so it really might be monel. The basket is in perfect shape.
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Old 08-18-2016, 12:13 PM   #35
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I use a Groco ARG series strainer on my A/C, which runs almost all the time. It was eating the SS baskets almost yearly. I switched to a Monel basket, which still looks new after 2 years, not even any stains or discoloration. In hindsight, I suppose I could have chosen Plastic and saved some money, but Monel definitely makes a difference.

Here is a link to a list of replacement parts and gaskets for Groco strainers. It lists SS, Plastic and Monel replacements for most models.

YMMV
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Old 08-18-2016, 12:34 PM   #36
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Back in those days both Perko and Groco made center rod style strainers. The name and model number will be cast in it some where. They were proud of what they made.

As I recall, Groco always used a big wing nut and Perko used an acorn nut or wing nut.
At any rate, if you want to disassemble it and measure the clear cylinder, I'll check to see if either Groco or Perko has it available. I need the diameter and height.

With the crazing in the cylinder that you describe, it's time to replace it. If you can't get a new cylinder (and gaskets) it's time for a new strainer.
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