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  #1  
Old 02-24-2014
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Blocked Raw Water Intake

Hello All...

This past weekend I had the luxury of sucking up a jellyfish in through the raw water intake for the engine. Completely stopped the flow of water to the engine. After first checking the impeller on my beloved Sherwood pump (boy do I dislike that thing!) with no success in improving water flow, I found that the tentacles made it to the strainer, but the body of the jellyfish was stuck somewhere between the the hull and the seacock. Abosultely no water was getting to the strainer. We were at anchor so after a lengthy period of time trying to remove the blockage with a folded-up rounded wire, my jiggling down the seacock finally worked and in came a flood of water.

I know that this is something that is bound to happen from time to time...but does anyone have any better techniques/tools for removing obstructions between the hull and seacock? With the presence of numerous jellyfish in the water...I was not exactly excited to go over the side...
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Old 02-24-2014
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Re: Blocked Raw Water Intake

Did it do this despite an external strainer? or do you have an open intake through hull?

We sucked up a shiner in a similar manner once, enough blockage to starve the cooling system but when we tried to blow it back out it 'leaked by' enough to be ineffective and we ended up going for a swim. We had been trying to blow it back out with the inflatable dinghy pump in 'inflate' mode. This idea may have been more effective with a more solid blockage. Such blockages seem to respond to being 'backflushed' best. If you could've gotten a hose from your pressure water system there to do the same thing that might work too. But I think keeping the critters out of the piping/hosing in the first place is the best defence.

Jellyfish, though, can probably get sucked up through almost anything.
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Old 02-24-2014
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Re: Blocked Raw Water Intake

Fin fishes seem to be one way operations. They go in just fine but don't come out backwards worth spit. Their fins get suck if the hole is too small. Not much applicable experience with jelly fish.
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Re: Blocked Raw Water Intake

I do not believe there is an external strainer on the through hull...I believe it is open...That was a thought I had...whether adding some type of external screen/strainer on the through hull is a good idea. However, I wasn't sure if that would be more prone to blockage by allowing oysters or other critters/sea life to attach themselves to...

I didn't think of trying to blow the blockage back out with an air pump...didn't have a pump on board anyways, but we do have one that could be taken aboard...
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Re: Blocked Raw Water Intake

The jellyfish was quite a messy situation...it seemed that every attempt to pull it out/loosen it only resulted in long stringy tentacles coming out...now I have even more reason to dislike them!
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Old 02-24-2014
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Re: Blocked Raw Water Intake

I have a shortened length of broom handle I have for that very eventuality. It fits through the seacock and is long enough that I can detach the intake and hold the end of the hose above the waterline.

Strangely I have never had to use it (perhaps this post will change all that)

I removed the external strainer last year after reading ManeSails thoughts on the matter: External Strainers - OMG Photo Gallery by Compass Marine at pbase.com
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Re: Blocked Raw Water Intake

Our problem is kelp, especially the air bladders, just happens I sell a specially designed tool for the purpose. They come in packs of two in case you slip and launch one like a torpedo.
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Re: Blocked Raw Water Intake

I sail in the Raritan Bay/Atlantic Ocean area. I've had external scoop strainers on the intakes of both boats I've owned. Believe me, sailing through those waters after heavy rains with all the floating debris in the water gives one something to think about. I have never had a problem with the raw water intake sucking in any floating debris. Also, no problems with jellyfish entering the intake when sailing through schools of jellyfish in the latter part of the summer. Yearly maintenance of the intake strainer can help prevent growing blockages around the strainer.
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Old 02-25-2014
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Re: Blocked Raw Water Intake

i checked the water intake on a power boat that came to lake superior from the northern west coast. the engine temp would go up every time you tried to run at cruising speed. it did not have an outside screen on the intake. the sea water strainer was clean. i finally found pine cones in the 90 degree elbow on the sea water intake at the strainer after cleaning them out it worked fine.
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Old 02-25-2014
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Re: Blocked Raw Water Intake

Thanks for the replies...I guess its one of those things that I'll have to deal with now and again...does anyone have experience blowing air with an air pump to try and force it out that Faster described? Is the air pressure sufficient? The pump could either be a manual dinghy pump or a 12v dinghy pump...
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