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Last weekend, my raw-water cooling system got clogged again. This seems to happen about once each year. It only seems to happen when the boat is not moving as when the engine is idling at the mooring or just started. A clump of seaweed gets stuck in the through-hull. There are only two reliable ways to unclog the through-hull, either dive under the boat and pull the weed out or back-flush it with a water hose. I’ve tried using the shower hose to back-flush but it doesn’t seem to have enough flow. I need to bring the boat to a dock and use a garden-hose. Here in the northeast, the water is typically cold and I’m reluctant to dive to pull the weed, so backflushing is the beast solution. I bought a sink drain snake but I haven’t tried it yet. My guess is that simply pushing the clog out an inch or two will only result in the weed getting sucked right back in.
I’m thinking of adding an external screen to the outside of the hull. I’m not sure that this will cure the problem however. The weed might just as easily get stuck on the screen. Has anyone installed one of these and have comments?
http://www.defender.com/product.jsp?path=-1|311|314196&id=673926
Rich
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Rich,
Unabated had a screen like that when I purchased her. Never had an issue and sodus bay is very weedy esp. at the dock.
AlanSent from my iPhone
On Jul 16, 2013, at 12:55 PM, wrote:
Last weekend, my raw-water cooling system got clogged again. This seems to happen about once each year. It only seems to happen when the boat is not moving as when the engine is idling at the mooring or just started. A clump of seaweed gets stuck in the through-hull. There are only two reliable ways to unclog the through-hull, either dive under the boat and pull the weed out or back-flush it with a water hose. I’ve tried using the shower hose to back-flush but it doesn’t seem to have enough flow. I need to bring the boat to a dock and use a garden-hose. Here in the northeast, the water is typically cold and I’m reluctant to dive to pull the weed, so backflushing is the beast solution. I bought a sink drain snake but I haven’t tried it yet. My guess is that simply pushing the clog out an inch or two will only result in the weed getting sucked right back in.
I’m thinking of adding an external screen to the outside of the hull. I’m not sure that this will cure the problem however. The weed might just as easily get stuck on the screen. Has anyone installed one of these and have comments?
http://www.defender.com/product.jsp?path=-1|311|314196&id=673926
Rich
BlackSheep #47_______________________________________________
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Rich,
I was advised against using a scoop type screen on my engine intake
thru-hull by Deatons Yard in Oriental, NC. The reasoning was that the
scoop (mine was a slightly larger Groco), when sailing, could force water
through the system and eventually get water into the exhaust system and
into the cylinders.
I was skeptical of this reasoning, but unwilling test it so I left the
strainer off the engine intake, and just put one on the intake for the
frig, A/C and galley faucet. That intake was the one that was causing me
trouble on the Chesapeake. I ran the frig whenever dockside and it would
usually clog with sea nettles once a week. Since installing the scoop
screen I have not had a single clog.
I left the engine intake without a screen and have never had a clog, but I
also use a 1-1/2″ thru-hull and strainer. That intake serves both the
Yanmar 4JH4-AE and the Northern Lights M642 generator, which I rarely run
simultaneously.
This is the screen I intended to use on my engine intake:
http://www.defender.com/product.jsp?path=-1|51|2234255|2234259&id=1806778
I think Tor put something similar on his engine intake, and has apparently
had no problems after 1,000s of miles of sailing. If that is so, the
advice I got is probably baseless.Regards,
John Stevenson
http://www.svsarah.comOn Tue, Jul 16, 2013 at 12:55 PM, wrote:
Last weekend, my raw-water cooling system got clogged again. This seems
to happen about once each year. It only seems to happen when the boat is
not moving as when the engine is idling at the mooring or just started. A
clump of seaweed gets stuck in the through-hull. There are only two
reliable ways to unclog the through-hull, either dive under the boat and
pull the weed out or back-flush it with a water hose. I’ve tried using the
shower hose to back-flush but it doesn’t seem to have enough flow. I need
to bring the boat to a dock and use a garden-hose. Here in the northeast,
the water is typically cold and I’m reluctant to dive to pull the weed, so
backflushing is the beast solution. I bought a sink drain snake but I
haven’t tried it yet. My guess is that simply pushing the clog out an inch
or two will only result in the weed getting sucked right back in.I’m thinking of adding an external screen to the outside of the hull. I’m
not sure that this will cure the problem however. The weed might just as
easily get stuck on the screen. Has anyone installed one of these and have
comments?http://www.defender.com/product.jsp?path=-1|311|314196&id=673926
Rich
BlackSheep #47_______________________________________________
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As originally built, my 424 had the strainer attached directly to the top of the sea-cock with a bronze elbow. Sea-grass would get caught at the elbow. When I repowered, I removed the elbow and installed a new strainer. Power boats running through shallow water cut gobs of the stuff which floats along the channels. Grass doesn’t seem to cause problems anymore. I find it in the strainer which is easy to clean out. It’s the seaweed that has bulbs on it that gets stuck in the through-hull. Local fishing boats drag the bottom and pull up the stuff.
I always thought the elbow mount used by Pearson was a bad idea. The strainer hangs on the pipe fitting. If this fails, the boat will flood. Even if the fitting never fails, it’s a natural place for stuff to get caught.
http://www.richardcarter.net/boat/pix/vdrivePan.JPGRich
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Thanks John,
I see two types of screens, one is round and the other is scooped. I see no mounting instructions so I don’t know which way the scoop is supposed to face. If I put the round type on, I don’t see how it could force water into the system. I’m not convinced that it won’t still get weed caught in it and eventually clog. Unlike the raw-water strainer, there is no convenient way to clean it however. Draggers pull up great clumps of weed. This sometimes finds its way into our mooring area. These are big clumps of weed. If I sucked one into even a 1.5 inch intake, I think it might clog though I might be able to pull the weed through.Rich
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Rich,
I agree, going with the round (no scoop) screen would not force water into
the system. The yard also said if I put the scoop on backwards (facing
aft) I would not have a problem, but that would defeat the purpose of the
scoop. For now I have left the engine intake un-screened. Again that
advice on the scoop screen may be baseless.I sized the screen such that even when half the screen was clogged by
debris I would still have full flow into my 1-1/2″ thru-hull. I recommend
doing the same with the round screen.
I think you will find that most of the debris that might collect on the
screen will be brushed off once you are underway.
I don’t know which is worse for clogging seawater systems, weeds or sea
nettles, but I am sure the sea nettles are worse to remove. My frig would
suck in 2 or 3 then they would die and turn into super glue. Often they
didn’t get to the strainer and just die in the hose from the valve. With
the screen on this intake I’ve never had a sea nettle clog the system.Regards,
John Stevenson
http://www.svsarah.comOn Tue, Jul 16, 2013 at 1:31 PM, wrote:
Quote:Thanks John,
I see two types of screens, one is round and the other is scooped. I see
no mounting instructions so I don’t know which way the scoop is supposed to
face. If I put the round type on, I don’t see how it could force water
into the system. I’m not convinced that it won’t still get weed caught in
it and eventually clog. Unlike the raw-water strainer, there is no
convenient way to clean it however. Draggers pull up great clumps of weed.
This sometimes finds its way into our mooring area. These are big clumps
of weed. If I sucked one into even a 1.5 inch intake, I think it might
clog though I might be able to pull the weed through.Rich
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The whole ‘forcing water into the engine’ thing is, in my mind, bs. The
amount of pressure required to force water through the whole system
including the raw water pump is ridiculously high. By that I mean 10s of
pounds per square inch – far more than you could ever generate moving at 8
knots through the water. There are boats that use speed through the water
to cool engines but they move very fast and have very large scoops.But I could be wrong.
Bob
On Tue, Jul 16, 2013 at 1:56 PM, John Stevenson wrote:
Rich,
I agree, going with the round (no scoop) screen would not force water into
the system. The yard also said if I put the scoop on backwards (facing
aft) I would not have a problem, but that would defeat the purpose of the
scoop. For now I have left the engine intake un-screened. Again that
advice on the scoop screen may be baseless.I sized the screen such that even when half the screen was clogged by
debris I would still have full flow into my 1-1/2″ thru-hull. I recommend
doing the same with the round screen.
I think you will find that most of the debris that might collect on the
screen will be brushed off once you are underway.
I don’t know which is worse for clogging seawater systems, weeds or sea
nettles, but I am sure the sea nettles are worse to remove. My frig would
suck in 2 or 3 then they would die and turn into super glue. Often they
didn’t get to the strainer and just die in the hose from the valve. With
the screen on this intake I’ve never had a sea nettle clog the system.Regards,
John Stevenson
http://www.svsarah.comOn Tue, Jul 16, 2013 at 1:31 PM, wrote:
Thanks John,
I see two types of screens, one is round and the other is scooped. I see
no mounting instructions so I don’t know which way the scoop is supposedto
face. If I put the round type on, I don’t see how it could force water
into the system. I’m not convinced that it won’t still get weed caughtin
it and eventually clog. Unlike the raw-water strainer, there is no
convenient way to clean it however. Draggers pull up great clumps ofweed.
This sometimes finds its way into our mooring area. These are big
clumps
Quote:of weed. If I sucked one into even a 1.5 inch intake, I think it might
clog though I might be able to pull the weed through.Rich
Original Message
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Silverheels had no thru-hull screens when I got her. I installed a big one
over the engine intake. It may be what you’re calling a scoop. (The wifi
where I’m anchored right now is too weak to visit the URL’s you guys are
providing as illustrations.) My bronze screen cover is shaped like a wedge
of cheese and perforated all over with small holes. I mounted it with the
tapered end facing forward. Perhaps this provides some scooping effect, but
it has not caused any problems in 6 years that I know of, and nothing has
ever clogged that intake. I put a half-round bronze screen cover over
Silverheels only other intake thru-hull, which feeds the seawater intake
manifold that services everything that uses seawater besides the engine.
Nothing has ever clogged that, either.I don’t sail with nettles or masses of weeds, but the ocean contains of all
kinds of debris including plastic. I’ve always thought some kind of screen
is necessary over intake thru-hulls.Tor
Silverheels, P-424 #17
http://www.silverheels.us
Quote:
Original Message
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Bob,
I’m at least skeptical. However I noticed that MainSail (Compass Marine)
posted the same warning on a forum a few years ago (
http://www.cruisersforum.com/forums/f115/external-raw-water-strainer-65505.html).
This guy is pretty knowledgeable, and generally not an alarmist.Regards,
John Stevenson
http://www.svsarah.comOn Tue, Jul 16, 2013 at 3:15 PM, Robert Fine wrote:
The whole ‘forcing water into the engine’ thing is, in my mind, bs. The
amount of pressure required to force water through the whole system
including the raw water pump is ridiculously high. By that I mean 10s of
pounds per square inch – far more than you could ever generate moving at 8
knots through the water. There are boats that use speed through the water
to cool engines but they move very fast and have very large scoops.But I could be wrong.
Bob
On Tue, Jul 16, 2013 at 1:56 PM, John Stevenson <
wrote:
Rich,
I agree, going with the round (no scoop) screen would not force waterinto
the system. The yard also said if I put the scoop on backwards (facing
aft) I would not have a problem, but that would defeat the purpose of the
scoop. For now I have left the engine intake un-screened. Again that
advice on the scoop screen may be baseless.I sized the screen such that even when half the screen was clogged by
debris I would still have full flow into my 1-1/2″ thru-hull. Irecommend
doing the same with the round screen.
I think you will find that most of the debris that might collect on the
screen will be brushed off once you are underway.
I don’t know which is worse for clogging seawater systems, weeds or sea
nettles, but I am sure the sea nettles are worse to remove. My frigwould
suck in 2 or 3 then they would die and turn into super glue. Often they
didn’t get to the strainer and just die in the hose from the valve. With
the screen on this intake I’ve never had a sea nettle clog the system.Regards,
John Stevenson
http://www.svsarah.comOn Tue, Jul 16, 2013 at 1:31 PM, wrote:
Thanks John,
I see two types of screens, one is round and the other is scooped. Isee
no mounting instructions so I don’t know which way the scoop is
supposed
to
face. If I put the round type on, I don’t see how it could force water
into the system. I’m not convinced that it won’t still get weed caughtin
it and eventually clog. Unlike the raw-water strainer, there is no
convenient way to clean it however. Draggers pull up great clumps ofweed.
This sometimes finds its way into our mooring area. These are big
clumps
Quote:of weed. If I sucked one into even a 1.5 inch intake, I think it might
clog though I might be able to pull the weed through.Rich
Original Message
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I agree, in order to force water through the engine you’d have to push past the water pump impellers.
AlanSent from my iPhone
On Jul 16, 2013, at 3:43 PM, John Stevenson wrote:
Bob,
I’m at least skeptical. However I noticed that MainSail (Compass Marine)
posted the same warning on a forum a few years ago (
http://www.cruisersforum.com/forums/f115/external-raw-water-strainer-65505.html).
This guy is pretty knowledgeable, and generally not an alarmist.Regards,
John Stevenson
http://www.svsarah.comOn Tue, Jul 16, 2013 at 3:15 PM, Robert Fine wrote:
The whole ‘forcing water into the engine’ thing is, in my mind, bs. The
amount of pressure required to force water through the whole system
including the raw water pump is ridiculously high. By that I mean 10s of
pounds per square inch – far more than you could ever generate moving at 8
knots through the water. There are boats that use speed through the water
to cool engines but they move very fast and have very large scoops.But I could be wrong.
Bob
On Tue, Jul 16, 2013 at 1:56 PM, John Stevenson <
wrote:
Rich,
I agree, going with the round (no scoop) screen would not force waterinto
the system. The yard also said if I put the scoop on backwards (facing
aft) I would not have a problem, but that would defeat the purpose of the
scoop. For now I have left the engine intake un-screened. Again that
advice on the scoop screen may be baseless.I sized the screen such that even when half the screen was clogged by
debris I would still have full flow into my 1-1/2″ thru-hull. Irecommend
doing the same with the round screen.
I think you will find that most of the debris that might collect on the
screen will be brushed off once you are underway.
I don’t know which is worse for clogging seawater systems, weeds or sea
nettles, but I am sure the sea nettles are worse to remove. My frigwould
suck in 2 or 3 then they would die and turn into super glue. Often they
didn’t get to the strainer and just die in the hose from the valve. With
the screen on this intake I’ve never had a sea nettle clog the system.Regards,
John Stevenson
http://www.svsarah.comOn Tue, Jul 16, 2013 at 1:31 PM, wrote:
Thanks John,
I see two types of screens, one is round and the other is scooped. Isee
no mounting instructions so I don’t know which way the scoop is
supposed
to
face. If I put the round type on, I don’t see how it could force water
into the system. I’m not convinced that it won’t still get weed caughtin
it and eventually clog. Unlike the raw-water strainer, there is no
convenient way to clean it however. Draggers pull up great clumps ofweed.
This sometimes finds its way into our mooring area. These are big
clumps
Quote:of weed. If I sucked one into even a 1.5 inch intake, I think it might
clog though I might be able to pull the weed through.Rich
Original Message
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Tor’s experience convinces me that the warnings are overblown, but I think
if I ever put a screen on the engine intake it be a round one that is
over-sized and can be opened to clean the thru-hull. No sense in tempting
fate.Regards,
John Stevenson
http://www.svsarah.comOn Tue, Jul 16, 2013 at 3:46 PM, Alan wrote:
I agree, in order to force water through the engine you’d have to push
past the water pump impellers.
AlanSent from my iPhone
On Jul 16, 2013, at 3:43 PM, John Stevenson
wrote:Bob,
I’m at least skeptical. However I noticed that MainSail (Compass Marine)
posted the same warning on a forum a few years ago (http://www.cruisersforum.com/forums/f115/external-raw-water-strainer-65505.html
).This guy is pretty knowledgeable, and generally not an alarmist.
Regards,
John Stevenson
http://www.svsarah.comOn Tue, Jul 16, 2013 at 3:15 PM, Robert Fine wrote:
The whole ‘forcing water into the engine’ thing is, in my mind, bs. The
amount of pressure required to force water through the whole system
including the raw water pump is ridiculously high. By that I mean 10sof
pounds per square inch – far more than you could ever generate moving
at 8
knots through the water. There are boats that use speed through the
water
to cool engines but they move very fast and have very large scoops.
But I could be wrong.
Bob
On Tue, Jul 16, 2013 at 1:56 PM, John Stevenson <
wrote:
Rich,
I agree, going with the round (no scoop) screen would not force waterinto
the system. The yard also said if I put the scoop on backwards (facing
aft) I would not have a problem, but that would defeat the purpose ofthe
scoop. For now I have left the engine intake un-screened. Again that
advice on the scoop screen may be baseless.I sized the screen such that even when half the screen was clogged by
debris I would still have full flow into my 1-1/2″ thru-hull. Irecommend
doing the same with the round screen.
I think you will find that most of the debris that might collect on the
screen will be brushed off once you are underway.
I don’t know which is worse for clogging seawater systems, weeds or sea
nettles, but I am sure the sea nettles are worse to remove. My frigwould
suck in 2 or 3 then they would die and turn into super glue. Often
they
didn’t get to the strainer and just die in the hose from the valve.
With
the screen on this intake I’ve never had a sea nettle clog the system.
Regards,
John Stevenson
http://www.svsarah.comOn Tue, Jul 16, 2013 at 1:31 PM, wrote:
Thanks John,
I see two types of screens, one is round and the other is scooped. Isee
no mounting instructions so I don’t know which way the scoop is
supposed
to
face. If I put the round type on, I don’t see how it could force
water
into the system. I’m not convinced that it won’t still get weed
caught
in
it and eventually clog. Unlike the raw-water strainer, there is no
convenient way to clean it however. Draggers pull up great clumps ofweed.
This sometimes finds its way into our mooring area. These are big
clumps
of weed. If I sucked one into even a 1.5 inch intake, I think it
might
Quote:Quote:Quote:Quote:clog though I might be able to pull the weed through.Rich
Original Message
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A lot of boats here on chesapeake have these big round strainers over genset intake thru hulls to prevent sea nettle jellyfish from stopping water flow. I think they work by dispersing the flow sufficiently that the jellyfish aren’t held against the thru hull.
Might want to bear in mind that barnicles love to grow inside the strainers and they might need periodically to be cleaned. I seem to remember seeing one that was hinged for this purpose.
Quent -
No need to hinge a screen. They’re usually held to the hull by several
screws. Easy enough to unscrew them during haul-out and clean things up
inside. I’ve found that spraying bronze – screens, props, shafts, etc – with
Petit Barnacle Barrier, a spray-on zinc product, not only serves as an
anode, but also acts like a primer and enables copper-based bottom paint to
stick to the bronze fittings long-term – even on the propeller! So my
screens are anti-fouled and don’t tend to fill up with critters.Tor
Silverheels, P-424 #17
http://www.silverheels.us
Quote:
Original Message
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Tor, are you saying that you apply bottom paint over the Pettit Zinc Coat Barnacle Barrier 1792 ? The description through Jamestown Distr. says not to, but I’d take your word on it if it has been sticking for you. I’ve always painted inside and out of my bronze clam shell shaped strainers and never had problems, other than I remember a few barnacles always finding it comfy. Never enough to make it a problem between haul outs.
@Tor wrote:
No need to hinge a screen. They’re usually held to the hull by several
screws. Easy enough to unscrew them during haul-out and clean things up
inside. I’ve found that spraying bronze – screens, props, shafts, etc – with
Petit Barnacle Barrier, a spray-on zinc product, not only serves as an
anode, but also acts like a primer and enables copper-based bottom paint to
stick to the bronze fittings long-term – even on the propeller! So my
screens are anti-fouled and don’t tend to fill up with critters.Tor
Silverheels, P-424 #17
http://www.silverheels.us
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I hadn’t seen that Jamestown warning about painting over the zinc spray. So,
yes, I put copper-based antifouling over it and was amazed at how well the
bottom paint stuck, even (as I said) on the prop blades. I sprayed & painted
my bronze screens inside & out, too.Putting zinc anode in between bronze (which I believe contains copper) and
copper-based bottom paint does seem like a potential electrolysis issue,
although the zinc is what’s going to go first. Anyway, last haul-out I
cleaned and re-painted the bronze and saw no problems.Tor
Silverheels, P-424 #17
http://www.silverheels.us
Quote:
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Good morning ALL – Tor, at the time I met you in the Bahamas, I was not
using bottom paint over my Pettit Zinc Coat Barnacle Barrier 1792 per
instructions and with great success. At haul out the follow the following fall,
growth on the prop was virtually little to none.
As you know, I work the summers at WEST and this stuff flies off the shelf
in the spring/fall and has left “Prop Speed” dead in the water. I have
since learned that it is the same Petit product as their transducer paint,
simply re-packaged because of its success and marketed as “Barnacle Barrier.”
Paint your prop as well if you wish, but doing so is superfluous and may
indeed impede the Barnacle Coat’s effectiveness.~~~ ~ (_~~ (_~ ~ ~ fair winds ~ ~ (_
Capt Bill Tice, aboard s/v CHARISMAIn a message dated 7/17/2013 4:58:31 A.M. Eastern Daylight Time,
writes:Pettit Zinc
Coat Barnacle Barrier 1792
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I use the same Zinc based spray paint on my stainless prop. I follow with a coat of tin based outdrive spray paint. This keeps growth off the prop. The outdrive paint seems to adhere better if I first coat with the zinc spray paint. The zinc paint alone works OK but not as well as the tin paint.
Rich
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Good to know. Thanks, Rich!
On Wed, Jul 17, 2013 at 9:33 AM, wrote:
Quote:I use the same Zinc based spray paint on my stainless prop. I follow with
a coat of tin based outdrive spray paint. This keeps growth off the prop.
The outdrive paint seems to adhere better if I first coat with the zinc
spray paint. The zinc paint alone works OK but not as well as the tin
paint.Rich
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This just keeps getting better.
Thanks,
Tor
Silverheels, P-424 #17
http://www.silverheels.us
Quote:
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Good info, Bill. Thanks. Next time I’ll do it au natural.
Tor
Silverheels, P-424 #17
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haha – your mileage may vary!
Stay safe…~~~ ~ (_~~ (_~ ~ ~ fair winds ~ ~ (_
Capt Bill Tice, aboard s/v CHARISMAIn a message dated 7/17/2013 5:03:41 P.M. Eastern Daylight Time,
writes:Good info, Bill. Thanks. Next time I’ll do it au natural.
Tor
Silverheels, P-424 #17
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