Screen over raw water intake.

[Simi 60]

A few days back I had a preemptive water temp alarm go off at 45c . water flow was down so cleaned the weed screen and continued.

While that improved the water flow marginally it turns out the main offender was a blockage outside so this morning fired up the hookah and sorted it out.

Big lump of something that as soon as I touched it with a scraper it dropped off, so I doubt it was growing.
To my surprise, there is no screen/scoop over the raw water intake and no evidence of there ever being one.

Normal or not?

 

[Simi 60]

Just found this
Some yes some no

http://www.trawlerforum.com/forums/s31/your-raw-water-intake-7421.html

 

[psneeld]

I have had them and hate them.

No way to reem out from inside the boat.

My secret is to oversize the thru hull by at least 2X the required hose intake and the flow is so little, not much gets sucked up. If it does, clean the strainer, pull the hose and ramrod the through hull all from the inside.

I have 15,0000 miles on my trawler with only one instance of a blockage...3 small fish swam up and clogged the inside strainer....

Plus thousands of hours on an assistance towboat where the regular bottom strainer got clogged and I swirched to the non screened through hull to finish the tow and get home.

Marine Sail or whatever his new site is callex has some good insight on external strainers.

 

[LaBomba]

I had the exact same thing happen to me in 2016. Last spring I added a scoop to the bottom. The weeds on mine were sucked right up in the hole tightly. Had to put the washdown hose down the inlet hose to unblock. I feel better now.

 

[Simi 60]

No access on the inside for us.
Intake has a 90degree elbow and short run of stainless pipe to the strainer which is now in a convenient and easily accessible spot.

When we got the boat the strainer needed a midget contortionist to access so it was changed on the initial inspection/survey lift.

 

[psneeld]

have access over the through hull at all?

 

[Simi 60]

have access over the through hull at all?

Nope, 90 degree elbow and a short run of stainless pipe to strainer.
Gate valve on elbow and strainer

Like I said, need to be a contortionist midget to access through hull and first gate valve, hence the short run of stainless to the new position.

 

[HopCar]

Some boat builders are installing Groco APHS external strainers and eliminating the traditional internal sea strainer. I installed one on Possum but left the sea strainer inside. It got about a year of use and I never had to clean the sea strainer. https://www.groco.net/products/raw-water-strainers/hull-strainer/aphs-series

 

[D.Duck44]

If you install an internal intake strainer above waterline with a straight pipe run down to the seacock, you can just take the lid off and rod it out when necessary.

 

[Insequent]

You could replace the 90° elbow with a T. Then part of the T will run straight down.

 

[Simi 60]

You could replace the 90° elbow with a T. Then part of the T will run straight down.

Certainly something to think on if it can be done without getting someone with a TIG in to cut and redo the plumbing I had done previously.

It would need a sealing cap on top and several feet of pipe to screw in to get the top above the waterline.

To do that I would have to remove a section of floor, wind gate valve about 50 turns to close, remove cap, screw in pipe and stuff a stick down it.

Reverse procedure and its time for an adult beverage

 

[psneeld]

The T iconfiguration s what. I was getting at...it doesnt "have" to be all the way above the waterline.... and a ball valve on top instead of a cap makes shutting off simple.

Used one for years when the other thru hull would get packed with sand, mud, grass, weed etc....would just swap the intake hose to its barb and open the through hull. By the time I got back to the dock, often the regular strainer would be washed out enough to use again. Plugged strainers never prevented me from accomplishing a tow despite working in an area that stopped others quite often.

Heck, even cleaning the front of the oil cooler was easier than trying to free up the external strainer.

The grates Hopcar posted are less prone to weed, but I and with oversized intakes, much less so. As far as opening...not sure how much of an underway feature that really is.

 

[Tom.B]

No access on the inside for us.

Intake has a 90degree elbow and short run of stainless pipe to the strainer which is now in a convenient and easily accessible spot.



When we got the boat the strainer needed a midget contortionist to access so it was changed on the initial inspection/survey lift.

Umm... yea... the sea strainer seems to be important enough that you should really consider moving them the next time you are on the hard. Is that possible?

 

[aboatman]

Some boat builders are installing Groco APHS external strainers and eliminating the traditional internal sea strainer. I installed one on Possum but left the sea strainer inside. It got about a year of use and I never had to clean the sea strainer. https://www.groco.net/products/raw-water-strainers/hull-strainer/aphs-series

My boat has that and it works well. It has one on the engine intake and one on the AC intake.

 

[GoneFarrell]

Are any of you with the T fitting setup using that to flush the heat exchanger with fresh water at end of boating season? Methinks this could extend operating time between cleanouts for my heat exchanger.

 

[Vashon_Trawler]

Are any of you with the T fitting setup using that to flush the heat exchanger with fresh water at end of boating season? Methinks this could extend operating time between cleanouts for my heat exchanger.

Yes, I have engine flush with bronze valve, hose, and stainless strainer. I simply spliced the line and clamped. It will also function as an emergency bilge. I fresh water flush after every trip. I purchased mine through yachtsofstuff.com

 

[Simi 60]

Umm... yea... the sea strainer seems to be important enough that you should really consider moving them the next time you are on the hard. Is that possible?

What, like cut another hole in the timber planking and do some type of fill on the old?
Then get someone in at great expense to cut and reweld the s/s pipework again?

No, can't see that happening, current through hull has been OK in that position since 1977.

This might be a suitable and faaaaar more affordable option

https://m.ebay.com.au/itm/Drill-Pow...473273&hash=item4412798d7f:g:-OQAAOSwA~VaL3CK

 

[diver dave]

Some boat builders are installing Groco APHS external strainers and eliminating the traditional internal sea strainer. I installed one on Possum but left the sea strainer inside. It got about a year of use and I never had to clean the sea strainer. https://www.groco.net/products/raw-water-strainers/hull-strainer/aphs-series

That would have to have a throw away screen to work in a high fouling area, like S FL. I had that external weed strainer that was a large, tilted, bronze plate with 1/8" perforations, and it was close to a nightmare to keep growth off it. Yes, I used Trinidad and at the 12 month mark had even oysters on it.

 

[Simi 60]

That would have to have a throw away screen to work in a high fouling area, like S FL. I had that external weed strainer that was a large, tilted, bronze plate with 1/8" perforations, and it was close to a nightmare to keep growth off it. Yes, I used Trinidad and at the 12 month mark had even oysters on it.

My thoughts exactly.

 

[Lepke]

You can see the bonding wire between the strainer and thru hull. Without a metal connection, in similar, but bad installation, the zincs don't protect the strainer and the bronze will shed zinc becoming porous. The basket, too depending on the material.
My current boat had a rubber hose from the seacock to the strainer and another hose from the strainer to the salt water pump and no bonding. When inspecting the strainers (solid cast iron) the strainer baskets were gone. So the po had been running the engines w/o a strainer for years. I also had copper pipe sink drains I had to replace because there was no bonding with a hose connection. You could see the parts below the water line where the pipe was paper thin.

 

[Lepke]

Some boat builders are installing Groco APHS external strainers and eliminating the traditional internal sea strainer. I installed one on Possum but left the sea strainer inside. It got about a year of use and I never had to clean the sea strainer. https://www.groco.net/products/raw-water-strainers/hull-strainer/aphs-series

I went to their site. The screen is 304 stainless. I wonder how long that lasts submerged in salt water.

 

[Capt. Peter]

Easy fix for clogged raw water inlet screen

Twice in the last two weeks of cruising in the NW our boat started uo in the am overheating. Both times the problem turned out to be weeds in the inlet after spending a night in a marina.

After a long diagnosis process the first time, we launched the dinghy and scrubbed the face of the cooling inlet screen with a brush on a long handle. That did the trick.

The 2nd time we quickly ascertained that it had to be the inlet screen, loosened the coolant inlet hose coming into the tranny cooler, inserted and clamped a 1/2” flexible silicone hose into the coolant water hose, and blew out. The sounds and bubbles coming from under the hull told the story. All was well again.

It’s clear that there are way more weeds in marinas than there used to be…

 

[rwidman]

Some boat builders are installing Groco APHS external strainers and eliminating the traditional internal sea strainer. I installed one on Possum but left the sea strainer inside. It got about a year of use and I never had to clean the sea strainer. https://www.groco.net/products/raw-water-strainers/hull-strainer/aphs-series

I have the very same screens on my engine intake and AC intake. They work fine and don't seem to clog.

https://www.trawlerforum.com/forums/attachment.php?attachmentid=73426&stc=1&thumb=1&d=1519787797

 

[rwidman]

I went to their site. The screen is 304 stainless. I wonder how long that lasts submerged in salt water.

One of mine is 21 years old. In salt water.

 

[diver dave]

In high fouling waters, they r more trouble. I had to toss mine and put on internal grocos. Oysters set up camp inside and out.

 

[Dougcole]

Chiming in here late.


When we bought our boat there was no external screen on the inlet for the generator, only a Marine Hardware internal strainer. Something about the location of the through hull, I think maybe because it is close to the keel, causes weeds to collect under the hull around it. In weedy anchorages (like our favorite one in the Bahamas) on an outgoing tide the generator would shut down every 30 minutes to 2 hours, depending on how thick the floating weed was.


Additionally, it would jam with weed not only in the strainer basket but also in the through hull, the hose leading from the through hull to the elbow, the elbow, and in the inlet to the strainer itself. Clean out meant pulling the hose off of the strainer and the through hull, jamming a rod through the whole works and using needle nose pliers to pull the packed weeds out of the strainer inlet. No fun at all. Especially at Midnight, 3:00 AM, 4:00 AM etc.


We installed a groco mushroom type strainer over the inlet, the hinged kind you can open for cleaning. Fixed the issue. I haven't had a big problem with fouling, even when we had the boat at Sunset Bay in Stuart which is a VERY high fouling area.


On our last trip the Genset clogged so I dove under the boat to check it. The cover was gone as the hinge pin failed. Most likely in a rough gluf stream crossing, but who knows? It lasted five years, so I replaced it.


Oddly, I've never had one of my engine strainers clog, or the AC strainer which is the same size as the genset. No external screens on those.

 

[FF]

OF course for the folks that tire of the plugged dance there is always the keel cooler. for the engine coolant.

No more expensive than huge intake filters, and sea cocks that need servicing.

If the exhaust manifolds are part of the circuit , only a small pump is required to dump water into the exhaust stream.