Raw water intake blocked twice in a weekend - Just unlucky?

Jokani

Jokani

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On my Westerly Centaur I moved the raw water intake from an awkward to access quarter berth that required a 90 deg hosetail, to just inside the engine compartment with a seacock and filter that could be rodded if required, I thought I was being smart, but maybe not.

This weekend the filter and intake twice blocked weed, the second time required me to quickly anchor adjacent to a freighter near to Ipswich lock whilst I cleared the filter out. Not a situation I would care to repeat.

I have only about 50 engine hours since I swapped and way less than that in the previous location, so can't really draw a direct comparison.

Would placing it between the bilge keels, only just offset from the centerline/propellor make it more sucseptible to blockage?

Without moving its location, is there anything else I can do to mitigate the problem?

Only think I can think of is to fit something like a clamshell fitting just in front of the thruhull.
 
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I've frequently had this weed problem occur, and it seems to be the ribbon slimy stuff that is the cause. This last week has been the exceptional spring tides here in Portsmouth/Southampton and Solent locations where the tide does seem to climb the beaches and drag all the flotsam into the waterways; this, combined with the algae being generated by the long period of hot weather results in the blockages.
I had a Westerly Tiger and the raw water intake aperture on her was only about 12mm dia, so suction pretty good!
just good access about the only cure and clearing the strainer after each sail/motor the only way to keep it clear.
We saw several yachts with clouds of steam following them this last weekend, no prizes for guessing what and why!!

Ian
 
The weed on the Orwell and Stour this year is beyond awful. I have heard of at least 2 instances of breakdowns due to overheating.
 
I'm assuming yours is the filter fitted on the seacock, I removed mine and fitted a large filter above water level in the engine compartment. It's now very easy to check the filter and clean, no prodding. I checked mine a few days ago and was surprised at how much weed was in the filter which was easily visible as it has a transparent lid. The water flow was still though. In the R Deben.
 
Weed in the Blackwater is really bad too and caught us out when running our generator the other weekend. Last year it also blocked the engine.
 
You do not mention what type of outletskin fitting you have,I assume you have the 'open' through the hull standard fitting 'not' one with a bronze strainer guard,
if it is part of the raw water seacock then I would fit a 'Vetus' type, I fitted mine directly above the sea cock and could be rod it out in seconds
Worse case scenario is the blockage is in the seacock itself so I kept an exact length of hose so the existing one could be exchanged quickly to clear any blockage
Good luck
 
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Caer Urfa said:
You do not mention what type of outletskin fitting you have
Click to expand...

Here is a picture, it is just below the waterline, but is rated as such:

MD2020B-raw-water-strainer.jpg
 
Not sure why you installed that type rather than the more common Vetus type bottom entry and exit strainer. Much better then to have it above the waterline and vertically above the intake. That way you can take the top off and rod vertically if you do get a blockage. Won't of course prevent the blockage but at least make it easier to deal with it.
 
Tranona said:
Not sure why you installed that type rather than the more common Vetus type bottom entry and exit strainer.
Click to expand...

Hi Tranona, I did previously have a Vetus, but the seal wasn't alway that great, and needed vaseline or something similar, and I wanted to swap plastic for bronze.

Previously I'd had trouble with priming, so I also wanted a strainer that is rated for under the waterline use. since fitted I have not had a ny further priming issues.

It is fitted directly above the seacock, so I can rod vertically, just wish I didn't need to quite so often :-)

I might take up one of the previous suggestions and install a backup. More often than not I'm single handing so the easier I can make life the better.
 
Agree with Tranona much better to have a higher strainer AND in line not sure what you previous problem was as I had a Vetus bottom entry strainer for 16 years with no problems
mind some people have not refitted the top correctly and maybe cross threaded the thread and buggered the seal.
 
GaryCottam said:
Hi Tranona, I did previously have a Vetus, but the seal wasn't alway that great, and needed vaseline or something similar, and I wanted to swap plastic for bronze.

Previously I'd had trouble with priming, so I also wanted a strainer that is rated for under the waterline use. since fitted I have not had a ny further priming issues.

It is fitted directly above the seacock, so I can rod vertically, just wish I didn't need to quite so often :-)

I might take up one of the previous suggestions and install a backup. More often than not I'm single handing so the easier I can make life the better.
Click to expand...

OK, I see the point of doing it that way and it is easy to inspect - just don't like the idea of being below the waterline, but that can be managed.

Don't think the problem of weed is in anyway affected by the layout of the strainer - just Prof. Sod having fun in this unseasonal weather which seems to have resulted in greater weed growth. Equally installing a second intake is overkill.

Odds on that you recent troubles are just random.
 
Caer Urfa said:
You do not mention what type of outletskin fitting you have,I assume you have the 'open' through the hull standard fitting 'not' one with a bronze strainer guard
Click to expand...

This is very important! Just in case the OP is not sure what Caer Urfa means, your skin fitting should look like this...

1731400b.gif


and not like this...

DOORB.png


The fact that you can "rod" it if blocked sounds a bit odd, as the skin fitting would kinda stop that from happening unless you were using a rod that was literally only a few mm wide. Have you got the right skin fitting?
 
Iain C said:
This is very important! Just in case the OP is not sure what Caer Urfa means, your skin fitting should look like this...

1731400b.gif


and not like this...

DOORB.png


The fact that you can "rod" it if blocked sounds a bit odd, as the skin fitting would kinda stop that from happening unless you were using a rod that was literally only a few mm wide. Have you got the right skin fitting?
Click to expand...

My inlet skin fittings were like the upper one, the one you recommend, but had to remove all the bars so I could clean out all the little critters that took up residence and grew blocking the inlet.

I did have a faciliter to rod from inside but still could not clean then all out effectively.
 
The upper type has long gone out of favour because it restricts water flow and tends to cause blockages, made worse over the years by owners painting over with antifouling so further reducing water flow. Engine manufacturers are very clear in recommending a clear bore (as in the second image) of a minimum diameter (usually 3/4" on small diesels) to ensure adequate water flow.

The OPs setup is excellent for the rare occasion weed does block the intake accepting that water will come in until he replaces the top. The more common setup of the strainer above the waterline but immediately above the intake allows clearing without water getting into the boat. The OP has explained why he changed from this method.

So, to answer your question, he does have the right skin fitting.
 
Cool, I'll bow to other's engineering knowledge here. However, in 10 years with the upper type, I never once had a blockage, so it can't be all bad (although I was careful with the a/f and used a needle file to keep the "slots" at the correct size...)

Also, my current boat has a sail drive, and the manufacturer fitted intake holes on the leg are also very small with no ill effects...
 
Iain C said:
Cool, I'll bow to other's engineering knowledge here. However, in 10 years with the upper type, I never once had a blockage, so it can't be all bad (although I was careful with the a/f and used a needle file to keep the "slots" at the correct size...)

Also, my current boat has a sail drive, and the manufacturer fitted intake holes on the leg are also very small with no ill effects...
Click to expand...

Blockages are rare in most places, but common for example going through the canals. Like you, I have never had a blockage in either a conventional intake or a saildrive in 40 years boating. If you look at your saildrive intakes the total area is large and it would impossible to have that in one big hole as there is not space on the casting, but it is not ideal as there are other problems with the intakes such as beasties going in as fry then growing inside to block the waterways. Mussels often do this if you are located where mussels are common.

Think you will find just about all new boats with through hull intakes use plain skin fittings.
 
Cool...thanks for the heads up...I know you know your onions on this kinda thing. You live and learn!!
 
I have had the 'distinction' of two blockages with saildrives, the first was most likely a carrier bag or similar which we picked up just off Greenwich maritime museum.

The second was the type of weed mentioned in some the earlier posts which was cleared using the dinghy pump attached to the hose going into impeller.
 
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