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Old 02-10-2019, 08:07 AM   #21
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I have not dealt with Sea Chests in over 30 years, but I would think on a boat the upper portion would/should be above the waterline? A large ship, no.

I guess it doesn’t matter in this case, because he will find out soon enough.
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Old 02-10-2019, 04:58 PM   #22
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I have the same type of seachest as shown in the op. Also the same fear when I first opened it. The top of mine is above the water line and has a tubular strainer which lifts out for cleaning. Two lines come out of mine, one to engine raw water pump and one for flushing the head. Also have a spare that’s not being used. Before you unbolt it make sure to mark the top and side so the top goes back where it came from. Also, take it easy prying the top off so no damage to the gasket. My guess is yours is above the waterline.
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Old 02-15-2019, 01:09 PM   #23
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You can find the water level relative to the strainer height easily by closing the raw-water valve, removing the hose from the seawater strainer and holding the hose up at different levels while slowly opening the raw-water valve. You may have to add a bit of hose on to the end you have removed from the strainer as the existing length may not be high enough. But it will be very low pressure. This will give you some comfort level to know exactly where the water level is before opening Pandoras box.
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Old 02-15-2019, 01:17 PM   #24
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We have a sea chest on MOJO and the top is several inches above the waterline. I suspect yours is the same. One thing you may want to watch for - bubbles running along the hull from the bow can find their way into the sea chest and displace the water. Over time the sea chest can fill up with air such that unless the lines coming off the chest are very near the bottom, you will end up sucking air rather than water. The solution is to install a very small fitting (1/8", 3/32", etc.) in the top of the sea chest to act as a vent and run a line up well above the water line and leave it open to the atmosphere. You can put a valve in it to close it off if your want, but it's really not needed as long as the vent line is secured well above the waterline. This will allow any air that enters the sea chest to escape out the top.

Regarding the plastic fitting, It's probably fine, but I'd change it out to either Marelon or stainless steel at the next haul out. You can find stainless fittings at agricultural supply stores and places where food processing equipment is sold.
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Old 02-15-2019, 01:31 PM   #25
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We have a sea chest on MOJO and the top is several inches above the waterline. I suspect yours is the same. One thing you may want to watch for - bubbles running along the hull from the bow can find their way into the sea chest and displace the water. Over time the sea chest can fill up with air such that unless the lines coming off the chest are very near the bottom, you will end up sucking air rather than water. The solution is to install a very small fitting (1/8", 3/32", etc.) in the top of the sea chest to act as a vent and run a line up well above the water line and leave it open to the atmosphere. You can put a valve in it to close it off if your want, but it's really not needed as long as the vent line is secured well above the waterline. This will allow any air that enters the sea chest to escape out the top..
You have described the sea chest on our DF (and most DFs) perfectly. There is a 1/2" valved line coming off the top for air release.
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Old 02-15-2019, 02:12 PM   #26
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You have described the sea chest on our DF (and most DFs) perfectly. There is a 1/2" valved line coming off the top for air release.
What Sunchaser said️..... I leave the sea chest vent valve open on our DF44, and the static and running water level is normally about 10-12" below top.

Our DeFever sea chests are about 10"SQ ID, as seen forward of stbd engine in picture. Which brought a question to mind when looking at the OP's picture.... My raw water requirements obviously greatly exceed that of the OP's boat, and 4" standpipe would starve my systems.

Salty's sea chest feeds twin JD mains, 12KW generator, A/C R/W pump, and an anchor washdown pump. Not uncommon for all systems to occasionally be in use at the same time.Click image for larger version

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Old 02-15-2019, 02:20 PM   #27
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Actually to me the ugliest thing in that picture is the battery switch etc, in the bilge in the background. WTH is that all about?
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Old 02-15-2019, 02:30 PM   #28
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Why would the top be below the water level? That seems nuts.

I'm not sure it is, the perspective in that picture is off, but until I get back and measure I can't say either way.

My Bruce Roberts had one with the cap below the waterline. I was always afraid to sail into Mexico because I was afraid some idiot drug search team would insist that I remove the top. It was an 8" pipe to the bottom of the keel and at one time contained a forward looking sonar. Previous owner had scraped the sonar head off on a reef. It was scary to have it there!!!!
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Old 02-15-2019, 03:39 PM   #29
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Actually to me the ugliest thing in that picture is the battery switch etc, in the bilge in the background. WTH is that all about?
looks like a batt switch feeding an emergency start jumper solenoid. The issue being?? There could be some exposed +12V, however.
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Old 02-15-2019, 03:40 PM   #30
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I have 3, one for each engine and one for the fire pump.
They are below waterline but on top of the seacocks.
They all contain filters but are easy to remove and clean.
Never have to worry about anything getting into the raw water pumps.
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Old 02-15-2019, 06:10 PM   #31
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Actually to me the ugliest thing in that picture is the battery switch etc, in the bilge in the background. WTH is that all about?
Oh, if that was the worst sin. Or the only sin. This boat has lots of warts, but I got me a big ol' file and a batch of gumption/optimism/stupidity or whatever you want to call it.

If I have the time I might slow release (for fun) all the terrible hacks that have been done to her. Is there an award given out for this?
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Old 02-15-2019, 06:12 PM   #32
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Seems this might have turned into show me your seachest and I'll show you mine. You all have some great chests... ermm....
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Old 02-15-2019, 06:27 PM   #33
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Oh, if that was the worst sin. Or the only sin. This boat has lots of warts, but I got me a big ol' file and a batch of gumption/optimism/stupidity or whatever you want to call it.

If I have the time I might slow release (for fun) all the terrible hacks that have been done to her. Is there an award given out for this?
Call me crazy.....but I've always enjoyed working on my boats! She'll be ship shape before you know it, and you'll know every inch of her systems!
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Old 02-17-2019, 08:30 PM   #34
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Left side of the picture, stainless.

Questions:
  1. Can you take the top off normally, in other words just unbolt it and reach in and clean out gunk? I assume the waterline is below it (I'll verify of course)
  2. Is there or should there be a strainer in there? If there isn't when I crack it, is that a problem (I'd think so, although I see a strainer inline in places.
  3. Confirm that the plastic elbow at the bottom is a bad idea. I think it is, no valve and could break easily.
  4. Is it OEM? Add on?
  5. Is it a plus for the boat, or a liability?
  6. I probably forgot a question, general opining encouraged.



This is the second time I have seen this type sea chest setup recently. I ran into it while looking at a boat last year. A mid 30's foot Carver, I think. The set up on that boat was vastly different. The sea chest was heavily supported against a bulkhead and set atop a brass or bronze seacock. It had a screen in it that was shaped kind of like a basket. The top was roughly 12 inches or so above the water line. It had an air fitting on top. I was lead to believe it was for relieving air pressure and also for blowing debris out of the sea chest and/or the seacock. It had several 3/4 and 1-inch valves connected to it. I never looked to see where all of them went. Most went to AC systems and the genset. The engines had their own seacocks.
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Old 02-19-2019, 08:21 AM   #35
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So I dove in. Took a line off generator to find the waterline level, found out the top of the sea-chest was easily about 6-8" above the water line. Top came off easily.

Here is a picture of the top taken off, upside down.

There was nothing else inside except some floaties. I cleaned it all. I suspect since there are strainers attached to this sea chest, that there was no strainer inside. Although there are holes in this tube which could imply a hook to some basket or something... In any case it's cleaned, back together. I might figure out an sacrificial metal situation at some point, but the service folks told me that stainless bonded to the boat should not have an issue, and it is bonded...

I always wonder what the motivation to add something like this is. It doesn't seem any more capable than a sea strainer except maybe isolating the floating trash to the top rather than sucking it into a strainer...
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Old 02-19-2019, 10:04 AM   #36
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With 9 seacocks in different locations on my 40 footer, some with dedicated strainers, I can appreciate having a simpler solution, but I am trying to fully appreciate the value of a sea chest beyond a central location for some (but never all - e.g. head discharge) thru hulls and related seacocks or (less ideal) ball valves and assorted fittings. There will likely be longer hoses and maybe more fittings. And the same number of holes in the boat plus a larger one of the sea chest that I don't believe can be closed. So how is that better/safer I still wonder?
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Old 02-19-2019, 10:05 AM   #37
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So I dove in. Took a line off generator to find the waterline level, found out the top of the sea-chest was easily about 6-8" above the water line. Top came off easily.

Here is a picture of the top taken off, upside down.

There was nothing else inside except some floaties. I cleaned it all. I suspect since there are strainers attached to this sea chest, that there was no strainer inside. Although there are holes in this tube which could imply a hook to some basket or something... In any case it's cleaned, back together. I might figure out an sacrificial metal situation at some point, but the service folks told me that stainless bonded to the boat should not have an issue, and it is bonded...

I always wonder what the motivation to add something like this is. It doesn't seem any more capable than a sea strainer except maybe isolating the floating trash to the top rather than sucking it into a strainer...
That is a very large cored hull penetration.

Is the hull penetration properly installed? Usually a large section of core is removed, well beyond the bolt hole pattern circumference. Then rebuilt with epoxy and maybe in this case mat. How this penetration should have been properly made is a lot like a stabilizer install it would seem, with a lesser backing plate. That job initially would be above my pay grade to do it right.
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Old 02-19-2019, 10:10 AM   #38
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I tapped around this penetration when she was out of the water, and nothing screamed poorly done. The boat was neglected, but certain things were done right. In the end, I can't say either way, I have a lot of work to do to get to the point where I'll truly know.
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