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Old 06-04-2017, 07:27 PM   #1
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Sea Chest

I have a sea chest in my boat. Boat spent the winter on land.
When we put it in the water there was a hiss sound as the air in the sea chest was forced out.

There is a thick piece of what I assume to be Lexan on top of a relatively thick rubber gasket. Numerous bolts from the top down to washers and nuts on the bottom.

The Question: are these nuts/bolts supposed to be really tight or just tight enough to keep the Lexan and rubber gasket snug?

Mine are NOT really tight and I have no problem but just checking.

Ken
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Old 06-04-2017, 07:47 PM   #2
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Greetings,
Mr. k. "...hiss sound as the air in the sea chest was forced out." Being forced out to where? PAST the rubber gasket? If so I would suspect the "lid" is not tight enough or the gasket is compromised.

If the nuts/bolts are too loose there could be a danger of vibrating off while being too tight might compromise the integrity of the gasket rendering it non reusable. Maybe use of nyloc nuts would eliminate the possibility of the nut/bolt vibrating apart while still allowing sufficient compression of the gasket to stop leaks.



I've seen these available in stainless and they are usually considered single use but for your application they'd probably last years.
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Old 06-04-2017, 08:34 PM   #3
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The top of the sea chest should be above the waterline. The air would need to be bled off so that water could get to the through hulls. The top should be secure but I wouldn't tighten it to Godzilla torque because the Lexan could crack. In theory you can pull the Lexan top off to clean out a through hull while the boat is in the water. That is the beauty of the sea chest.
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Old 06-04-2017, 09:29 PM   #4
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FWIW, the top of my seachest is above the waterline, but it is secured airtight with about a dozen large bolts around the perimeter.
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Old 06-04-2017, 10:10 PM   #5
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Thanks. The top is above the waterline as should be. The screws are more snug than tight. Wasn't sure they had to be airtight or was snug OK.
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Old 06-05-2017, 08:27 AM   #6
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On my Defever44 the sea chest has a valve and vent line near the top to prevent air lock. If you had air escaping from the top flange when you launched, maybe your vent valve is closed.
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Old 06-05-2017, 08:55 AM   #7
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Quote:
Originally Posted by greysailor View Post
On my Defever44 the sea chest has a valve and vent line near the top to prevent air lock. If you had air escaping from the top flange when you launched, maybe your vent valve is closed.
Grey, what do you think- during launch I get it, but should the valve be open or closed when we're in big seas?
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Old 06-05-2017, 09:50 AM   #8
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Sunchaser....
I leave my seachest vent open on my boat. As long as the vent line discharges outside of the hull I can't see a problem with that. However if your vent line just runs up to the top of the engine room and you are pounding in rough seas, you may get a few spurts of seawater from it. My cruising grounds are much calmer though. ��
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Old 06-11-2017, 07:22 AM   #9
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Our sea-chest has a lexan cover with four bolts. We just snug them up.
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Old 06-11-2017, 08:01 AM   #10
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When we launched our Defever 44 last week, I was initially surprised to see the water level in the seachest well below the lowest through hulls at the bottom--with a very solid air pocket holding it there. In previous launches, I hadn't noticed this. I'd replaced the hardware securing the lexan top this time (using the same gasket) and torqued all 24 (!!!) bolts down snugly and evenly--but not aggressively. (Spottsville, I really envy four bolts!) Apparently that better seal made the difference. Bleeding the air out with the top seacock allowed the chest to fill quickly.

The seacock at the top of our seachest IS a drain for the stabilizer cooling water and refrigerator condensate. It's perhaps an inch above the water line, depending on the boat's loading and trim.
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Old 06-15-2017, 06:12 AM   #11
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Yes the four bolts with toggle nuts makes it easy to remove but we don't seal it. We leave the plug hole open. Under what conditions would you need it sealed? We have at least a foot from the top to the water level below.

Oh, by the way (before someone ask) the wire you see through the plug hole goes to a Maretron water temp gauge for measuring raw water temp.)
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Old 06-15-2017, 08:12 AM   #12
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Quote:
Originally Posted by Spottsville View Post
Yes the four bolts with toggle nuts makes it easy to remove but we don't seal it. We leave the plug hole open. Under what conditions would you need it sealed? When you go to sea ??
We have about sixteen bolts holding the polycarbonate cover onto our 1 sq ft sea chest. It is not uncommon to have big enough seas and resultant boat motion for sea water to forcibly push against the cover and gasket and spray a bit through the cover seam.
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Old 06-22-2017, 01:11 AM   #13
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I've never had any water of any kind come up out of the sea chest and I been in very rough seas (my bad). Mine is the same as Spottsville water level is 1+ foot below lid. Some Defever have chest with water lever at the top of the chest. I have a 1/2" threaded opening in the middle of the lid as a vent. If necessary I could plug it but not a issue.
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