Seatwater strainers

C

commander bill

Well-known member
Joined
Feb 4, 2009
Messages
292
Fluid Motion Model
C-248 C
Vessel Name
Lenabell
LENABELL still on trailer & I am trying to complete mods to get her back in water soon. I went to flush antifreeze from the AC & Genset seawater lines and clean the strainers & discovered one of the small plastic strainer cover for the GENSET was broken. I did a quick failure analysis and decided it had not frozen but was likely due to being overtightened. Must have been the first mate as I know I couldn't have done that. Anyway, does anyone know of a source for these small clear plastic covers. Might have had an existing flaw but who knows. Seems like a waist to have to buy a complete strainer to replace cheap plastic cover. I checked the cover on the AC seawater strainer and it was OK. Both strainers appear to be identical except that the GENSET has a finer mesh screen than the screen on AC strainer. I was not able to read the manufactor name on the strainer and it does not look like any stainer shown in any of the boat supplies catalogs I have (WM, BW, Defender, etc)
 
What kind of antifreeze did you use? Automotive antifreeze will slowly deteriorate the clear plastic cover and cause it to crack. Go to the below web site for "Sea Dog Line." Replace the installed screen with a 1/16" mesh screen to allow better water flow as a 50 mesh screen is to easily clogged with vary small particles resulting in an overheating generator.
Henry

http://www.sea-dog.com/PDF/364135.pdf
http://www.sea-dog.com/maincatalog.html
 
I was using automotive antifreeze. And before all the envirnomentalist jump onboard I drain and save the fluids before I launch the boat. I did not know about the impact of using automotive antifreeze. Also, the fine mesh strainer had required frequent cleaning several times during the season so I will consider replacing it with courser mesh.
 
Also note that the PDF sheet for the strainer says it should be mounted "above the water line". I don't know about yours, but mine are mounted below the water line such that if the plastic housing cracked, the boat could sink. I think I've got three of those: one on the air conditioner inlet, one on the generator and one on the deck washdown pump. Some later boats may have combined some of these into the bronze engine cooling strainer. Looks like another afternoon of re-plumbing to move the plastic strainers up higher so that if they crack open, the water won't run in. Otherwise, you must remember to close the through hull fittings when the boat is unattended to make sure it doesn't sink. I think the boating construction standards also do not allow plastic strainer housings to be used below the water line since they are prone to cracking or otherwise easily damaged and could let water in.
 
So, is this another thing i have to worry about doing? Re routing strainers or whatever? For those of us who are not the mechanics of this world these posts raise images of sinking while enjoying dinner or something.
Maybe Andrew could chime in on this...should i be telling my maintenance people something?

tom
 
I have been told that the R-25 now has NMMA certification. I wonder what NMMA had to say about those inexpensive (AKA cheap) raw water strainers being used below the waterline? On the plus side, they are made in the USA rather than China.
Henry
 
With a fairly early hull, number 59, it would interest me to know if i should take some action on this.

terraplane
 
You should close your sea cocks when leaving a boat unattended in the water. There are several reasons:

Sea cocks that are not exercised from time to time tend to corrode, freeze, and ultimately break off.

Rubber hoses age, crack, and fall off in 10 to 20 years.

Critters like to live up in holes, and shutting the sea cock limits how far up they can live. (Also a reason to shut them when the boat is on land.)

Marine toilets have a variety of parts that can stick, jam, or break, and have probably sunk more boats than any other single piece of equipment.

Last but not least, sea strainers can be damaged and let in more water than bilge pumps can remove. This is even true of higher end ones made of marine bronze and glass. The glass and the rubber gaskets are vulnerable parts.

If you put a sea strainer above water level and it is not air tight, you will wind up with an air bubble. That will be a real problem for some pieces of equipment such as air conditioners that may not be able to suck the bubble through. I would not do it.
 
terraplane":12ewy00z said:
With a fairly early hull, number 59, it would interest me to know if i should take some action on this.

terraplane
Click to expand...
Suggest you might ask the manufacturer about locating their strainers below the waterline. If your strainers are Sea-Dog contact the below.
Henry

techserv@sea-dog.com
phone 425-259-0194
 
Tom Ray is absolutely correct on this issue. This is why we use seacocks and I always reccomend shutting them off if they are stored in the water. This is a seadog strainer and you are welcome to order one direct from us here at the factory. Just send an email to the dealer you purchased the boat from and they can turn in a parts request form if thats the route you wish to choose.

Nmma or Abyc has nothing to say about using these sea strainers on our generators or airconditioners.
 
Andrew Custis":gxx7y7hv said:
Nmma or Abyc has nothing to say about using these sea strainers on our generators or airconditioners.
Click to expand...
I don't mean to dwell on the subject about using Sea-Dog strainers below the waterline. However, one tends to wonder why the manufacturer comes right out an says, "Filter should be mounted above water level line." Possibly they are trying to cover their hind sides in the event their in line strainer fails and the unthinkable happens.
The Polycarbonate lens probably failed because automotive Ethylene Glycol antifreeze was utilized rather than Propylene Glycol. Ethylene Glycol will cause Polycarbonate to crack and then fail.
Henry
 
I am sure that use of automotive antifreeze could lead to long term failure but in this case I am fairly sure I broke the cover by tightening too tight. The crack is completely contained in the threads away from the wetted surface in the filter body. I just wanted a replacement cover for the existing filter. WM has a part number that appears to be the same cover for about $5. I guess I will use the pink stuff in future.
 
Since I am putting together a spare parts kit to build an entire Ranger Tug, does anyone have the part number and order info to purchase a plastic cover for these strainers. (We already have a spare for the big seawater strainer that fees the engine, because my husband broke that on this first try and it took a few days to get a new one.)
I see one on the sea-dog site but would prefer to get it from West Marine. Or Ranger.

Sparky
 
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