Raw Water Strainer 101

ttmott

ttmott

PhD in OCD
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TECHNICAL Contributor
Apr 3, 2012
8,127
Space Coast Florida
Boat Info
2006 52 Sedan Bridge
Engines
Cummins QSM11
Whenever I pull a strainer assembly I usually rebuild it. I was taking some measurements to run new hard pipe sanitary lines and noticed the bridge HVAC/watermaker raw water strainer had a drip coming from the bottom of the bowl. Looking closer at it was a crack in the plastic filter bowl. It's one of those moments you think - what if this had failed. This picture looks benign and normal for a boat of seventeen years old right? Couldn't be further from the truth.
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So, I thought I stimulate some priorities to get these older strainers refurbished. If you live in Florida you know that it is a weekly thing to pull the HVAC strainer basket and clean it. How many notice the plastic handle on the basket gets broken and we just reuse it? How many of us just put it all back together and don't take a good look at it? Here are a few things to stir a bigger interest in these simple devices for not only proper function but to ensure the boat won't fill up with water and worst case go to the bottom.
First the basket and that plastic handle. It is that handle that when the cap is screwed down holds the basket in the housing body retainer; if not seated in the retainer and held down the basket will lift and the flotsam that needs to be captured in the basket is flowing all through the system.
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That bowl - age takes it's toll on the plastic and cracks will develop around the bolts attaching the bowl to the housing. Get under there and look closely at the plastic bowl. You definately don't want to see this but actually not that uncommon.
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So, maybe it is time to pull the strainer assemblies and get them refurbished. The bowl for this one is $75, a cap $30, and gasket kit $30. It's the cheapest piece of mind you can buy.
When refurbishing flat-file the mating surfaces to remove the hammer sins of the past.
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SKybolt said:
Tom have you thought of removing the strainers and replace them with south bay strainers? Ocean yacht's do not come with internal strainers at all and only these South Bay ones. You may not know them as South Bay, but as Rectangular Scoop Strainer.

https://www.go2marine.com/Rectangular-Scoop-Strainer-with-Slide-Out-Screen?quantity=1&fits=124

https://www.deepblueyachtsupply.com...y321Ikt9hDMUlhMnCXPP4V-aGfraztRcaAlsPEALw_wcB
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I take it these attach to the hull over the intakes?
 
I've seen those on the big blue water boats. But, in our area where grass and other growth are prevalent, they would be a problem to keep clear, I'm sure.
 
Carpediem44DB said:
I take it these attach to the hull over the intakes?
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Yes they come in different sizes to accommodate the through hull size. As mentioned Ocean Yacht's uses these and do not have any strainers inside the boat. The previous owner of my boat installed these on the AC and both engines. I use to check the engine strainers regularly but not so much any more, they never have anything in them. When it's time to replace the raw water hoes's I am considering removing the strainers.
 
ttmott said:
I've seen those on the big blue water boats. But, in our area where grass and other growth are prevalent, they would be a problem to keep clear, I'm sure.
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If you have any Ocean Yacht boats near you, you should talk with the owners and see what they say. My buddies boat is a 48 Ocean that came out of Palm Beach and has had zero issues.
 
SKybolt said:
If you have any Ocean Yacht boats near you, you should talk with the owners and see what they say. My buddies boat is a 48 Ocean that came out of Palm Beach and has had zero issues.
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The only one I've seen here is kept in the port on the other side of the locks; clean clear water. I saw them on a large boat in the yard my mechanic was working on, I don't know the owners. I'll get a photo of the strainer basket when I pull it again so you can see that it would be an issue with an underwater strainer.
 
I know a guy who’s AC strainer bottom fell off I guess from fatigue and the water just started pouring in luckily he was servicing the strainer at the time.
These things get brittle for sure good point Tom.
 
Havana Shamrock said:
I know a guy who’s AC strainer bottom fell off I guess from fatigue and the water just started pouring in luckily he was servicing the strainer at the time.
These things get brittle for sure good point Tom.
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The bottom falling off would not cause water to pour in anywhere. These are just a screen that covers the through hull fitting. The through hull is completely separate.
 
ttmott said:
The only one I've seen here is kept in the port on the other side of the locks; clean clear water. I saw them on a large boat in the yard my mechanic was working on, I don't know the owners. I'll get a photo of the strainer basket when I pull it again so you can see that it would be an issue with an underwater strainer.
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I guess it could be an issue. I have this on my AC strainer as well. And recently went to an area of the bay that has an incredible amount of jelly fish and clogged my strainer, the south bay on the outside of the hull, nothing on the inside at all. So I can say that it could be an issue, but that much grass I would think causes an issue no matter what strainer you have. I have a tee inside just after the through hull and before the inside strainer for blowing off anything that might get stuck to the bottom of the strainer. It is also the fitting I use for Barnacle Buster and how I dealt with the jelly fish.
 
@ttmott Either way, great thread on strainer maintenance and nice that you brought this light. You should add in how you keep the bronze looking so nice in the bilge of a boat. Your engine room looks cleaner then a new boat a year later.
 
SKybolt said:
@ttmott Either way, great thread on strainer maintenance and nice that you brought this light. You should add in how you keep the bronze looking so nice in the bilge of a boat. Your engine room looks cleaner then a new boat a year later.
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When I pull any of the bronze things from the boat that show corrosion, I mix a 20% solution of Muriatic acid (pool acid) and water and put that in a spray bottle. First clean the bronze with Z-Cleaner to remove any oils or wax then liberally spray on the acid solution and let it sit for about 20 minutes. Then scrub it with a SS wire brush (repeat if necessary) and rinse then soak in a bucket of baking soda and water. That's it. Before I reinstall a light coat of Corrosion X gets sprayed on. The last batch I did when we rebuilt all of the running gear.
IMG_5472 cropped.jpg
 
Our 320 had the external strainers never had an issue but if it did get clogged it would mean a dive on the boat. Was recently at a transient dock this summer with a ton of sea grass. Dockmates kept having to dive the boat to clear the clogs to their ac pickup. I just made it a routine to check and clean my strainer baskets twice a day from the comfort of my engine room. Not sure if neighbors had the external strainers but for me clearing from in the boat was very easy.
@ttmott, I didn't realize that the handle on the basket helped seat it in the bowl. This explains a lot as when I was clearing my strainers the sea grass had wedged it in as it was floating higher than it should be. Will be ordering a replacement, thanks! BTW my gen has one that is metal and my ac pickup has the plastic one. Similar make up for the caps as well (one is metal the other is plastic). Any reason for plastic vs metal?
 
I have recently completed the installation of a fresh water flush in line AFTER the strainers with ball valves.

This way, not only can I can flush the salt water out and leave a pickling of SALTAWAY in the raw water system, I can (and have on my 10 meter) the ability to BACKFLUSH any trash/debris/seaweed/plastic bag/whatever that may be in the system quickly and easily.

This really comes in handy when you are anchored out overnight and your AC or genny quits at 2 AM because it sucked up some seaweed and cant get enough raw water flow.

BEST !

RWS
 
Seems like the bowl could benefit from some metal "spreaders" that would distribute the clamping force more than just below the head of the screw.
 
SKybolt said:
The bottom falling off would not cause water to pour in anywhere. These are just a screen that covers the through hull fitting. The through hull is completely separate.
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I wasn’t referring to the South Bay strainers I’m well aware of them all my boats had them I was on SS for many years I’m talking about the inside strainer with the plastic basket .
 
Seems everyone is confusing which strainers Tom is talking about here. NOT the Buck Algonquin exterior scoop type strainer to block Eel grass etc.
he’s referring to the raw water strainer with the basket located in the ER . If not serviced this will sink your boat.
 
Havana Shamrock said:
Seems everyone is confusing which strainers Tom is talking about here. NOT the Buck Algonquin exterior scoop type strainer to block Eel grass etc.
he’s referring to the raw water strainer with the basket located in the ER . If not serviced this will sink your boat.
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Yes, a few post's up I asked why not try the South Bay instead. Not sure anyone confused them, just me derailing another thread.
 
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