Sea Chest

John Brownlee · Post by **John Brownlee** » Oct 13th, '09, 14:22

Capt. Patrick (or anyone else):

I'm going to install a sea chest in the Bertram to supply my two livewells with raw water. I'm tired of replacing the pumps, which now sit directly on top of the two through-hulls, and burn out after only a month or two.

I have seen many of these chests, including the ones at Tropic Star, and the pumps in them seem to last much longer. I was going to buy one from Fred Herman in Miami, but he has retired. I did find one at Hopkins Carter in Miami, though. Twin 2000 gph Rule bilge pumps, a 1 1/2" inlet and two 1 1/4" supply lines to the wells.

I'll have to replumb everything and install a new 1 1/2" seacock, but here's the question: does the chest need to be mounted higher than the seacock yet still below the waterline? Seems like that would make sense so air would pass though it.

And does anyone have a diagram on how to set one up? Any thoughts or help would be appreciated, thanks!

JB

Charlie J · Post by **Charlie J** » Oct 13th, '09, 14:36

john
i usred to go thru pumps every year. i finally went with the shurflow extreme blaster 5.3 gpm, i have it y wash down hose and bait well, going on 5 years now with out a problem.. bait well runs anywhere from 5 hrs to 8 hrs non stop. there about $200 i think

JP Dalik · Post by **JP Dalik** » Oct 13th, '09, 14:42

This is sort of the gold standard:

The fiberglass ones inevitably leak at some point. You will need to supply a vent above the water line to be sure you can fill the chest.

Bruce · Post by **Bruce** » Oct 13th, '09, 14:46

Doesn't need to be higher than the thru hull as the air can be purged by removing an outlet hose.

Also make sure the thru hull pickup has a speed scoop. Without it centrifical pumps such as bilge pumps are not self priming and will not suck the water at high speed.

This pump works well as a bait well circulating:
http://www.rule-industries.com/products ... /index.htm

Plumb right to thru hull.

CaptPatrick · Post by **CaptPatrick** » Oct 13th, '09, 15:58

John,

Basically a tub glassed to the hull, mostly below the water line. But the top should be high enough above the waterline, when the boat is at rest, so that it can be opened and cleaned without hauling the boat.

Rectangular is most convenient with as many valved through hole fittings as necessary. You can also have just one large fitting to the chest and manifold from that. An additional filter screen can be added over the port if deemed necessary.

Not shown in the diagram, is an 1/8" rubber gasket between the acrylic and the flange of the chest.

pacific marlin · Post by **pacific marlin** » Oct 13th, '09, 16:42

Sorry,
I do not understand this at all,

Am I right in saying that this device, deliberately forces water into
a holding tank, which then supplies said water to whatever?

Seems to me that unless this is 100% ,copper bottom,absolutley,without doubt etc, etc ,etc, add infinitum ,done properly (what ever is )?.

Then the Germans would have used this to scupper their fleet at Scapa Flow, rather than just open their sea cocks .

Perhaps I'm wrong but I wouldn't go there,

Sorry, no disrespect intended, just dumbfounded.

Ian.

Bruce · Post by **Bruce** » Oct 13th, '09, 17:01

Not really a holding tank. More of a central distribution box.

There are many factory boats that come with sea chests.

A good many of your large aluminum hull yachts also use them in the engine room area.

They work very well as it keeps all the valves in one area and allows for cleaning of thru hulls without going overboard.

pacific marlin · Post by **pacific marlin** » Oct 13th, '09, 17:14

Bruce,

would you put one in a B31?

Ian.

CaptPatrick · Post by **CaptPatrick** » Oct 13th, '09, 17:18

Ian,

Sea chests are quite common, especially on larger boats that may otherwise have as many as 15 or 20 through hull fittings scarttered around the hull. The sea chest is a simple way to get a large supply of clean raw water to a central location and then distribute it from there.

While not a beginner's project, they can be built correctly and with confidence...

would you put one in a B31?

Probably not, but I wouldn't be intimidated in the least to do so...

pacific marlin · Post by **pacific marlin** » Oct 13th, '09, 17:26

Capt Pat,

Thats good enough for me,

regards Ian.

Bruce · Post by **Bruce** » Oct 13th, '09, 17:51

would you put one in a B31?

If an owner wanted one, yes.

In my own, no. Only because there is not enough thru hulls to warrant the work involved in putting one in.

pacific marlin · Post by **pacific marlin** » Oct 13th, '09, 18:03

Would a single through hull and a manifold do a similar job?

CaptPatrick · Post by **CaptPatrick** » Oct 13th, '09, 18:45

pacific marlin wrote:Would a single through hull and a manifold do a similar job?

It would depend on the size of the through hull and the demand of the items manifolded from it... For example if you have three items requiring a 3/4" flow, that's 0.44" x 3 = 1.33" of demand, so your single through hull fitting would have to be 1.5" to supply all three items at once.

On a 30' boat there aren't many things requiring a constant supply of raw water, other than the main engines, generator, and livewell. I won't rob water from an engine, so a dedicated through hull for the livewell is installed. In all cases, the through hull fitting must be sized to meet the demand...

I also wouldn't pull water from a sea chest to supply engines or generator.

Pete Fallon · Post by **Pete Fallon** » Oct 13th, '09, 20:08

John,
I've been running a Rule 3000 gph pump, off of a 1-1/4" dedicated thru hull with scoop slotted strainer about a foot forward of the port transom, 6" off the centerline. This pump supplies 2- 40 gallon above deck oval poly plastic live wells, an 1-1/2'' tee fitting for the supply hoses for each well, then reduced to a 3/4" stainless gate valve style hose bib at the port and starboard cockpit side panels. Plenty of flow for both wells and a wash down hose, you can control the flow rate to each well, 4 years of use with no problems. Gravity fed over board discharge hoses out thru the old 1-1/4" above waterline transom fittings, all hoses are under the cockpit sole. Sea chest might be a pain in the butt, especially in weed prone areas.

Ironman · Post by **Ironman** » Oct 13th, '09, 20:32

John: I run a couple pumps for baittanks... My secondary pump below the waterline a (Rule 1100) was found sucking air a few times from cavitating or whatever.. I drilled a few 1/4 min holes in the front of the raw water scoop & that solved the dry running .
Hope this saves a lot of extra work
Wayne

Bruce · Post by **Bruce** » Oct 14th, '09, 09:36

I also wouldn't pull water from a sea chest to supply engines or generator.

If the sea chest is appropriatly sized, you'll have no issues.

I've got a few customers that have this setup factory.

Rawleigh · Post by **Rawleigh** » Oct 14th, '09, 09:44

Pete Fallon wrote:John,
I've been running a Rule 3000 gph pump, off of a 1-1/4" dedicated thru hull with scoop slotted strainer about a foot forward of the port transom, 6" off the centerline. This pump supplies 2- 40 gallon above deck oval poly plastic live wells, an 1-1/2'' tee fitting for the supply hoses for each well, then reduced to a 3/4" stainless gate valve style hose bib at the port and starboard cockpit side panels. Plenty of flow for both wells and a wash down hose, you can control the flow rate to each well, 4 years of use with no problems. Gravity fed over board discharge hoses out thru the old 1-1/4" above waterline transom fittings, all hoses are under the cockpit sole. Sea chest might be a pain in the butt, especially in weed prone areas.

Pete: Do you have the plastic Rule pump plumbed below the waterline? I don't trust any plastic below the waterline, even a plastic centrifugal pump. I want the pump above the waterline on mine!!

John Brownlee · Post by **John Brownlee** » Oct 14th, '09, 13:48

Thanks for all the good advice guys. I'm looking at a rectangular, self-contained chest that is essentially a fiberglass box with a clear acrylic lid. It doesn't get glassed to the hull as in Patrick's diagram but it does the same thing. It is fed by a single large hose from a seacock rather than from holes in the bottom of the boat. It has fiberglass tabs on it so you can screw it down wherever you want to mount it. It also has a small clear tube (actually aquarium air tubing) with a check valve in it so you can purge air from the system.

I think it will work fine as long as it's mounted below the waterline. I'm feeding two 40-gallon deck wells and need a lot of supply capacity. The dual 2000 gph Rule pumps ought to do it.

Capt.Frank · Post by **Capt.Frank** » Oct 14th, '09, 17:10

John,
Would like to see pic's when you get it done.

Thanks
Frank

Pete Fallon · Post by **Pete Fallon** » Oct 14th, '09, 18:54

Rawleigh,
The 3000 Rule is connected to the 1-1/4" sea cock with a 12" piece of Sheilds wire re-inforced hose, pump body is bolted horizonal to deck support, below the waterline about 18" above bottom of aft compartment. High water alarm switch in that compartment, intake hose can be taken off the thru hull fitting and the pump can be used as a back up bilge pump if needed. I don't hard couple anything plastic to the thru hulls, seen to many broken off pump bases over the years.

John Brownlee · Post by **John Brownlee** » Oct 27th, '09, 12:29

Just got the pump this morning and I'm attempting my first photo upload. Here goes nuthin.

As you can see, the sealed box houses two 1500 gph Rule bilge pumps. It's fed by a single 1 1/2" supply line and the pumps supply the wells through two 1 1/4" hose barbs. It's pressurized and has a relief valve (the clear tubing) for letting out any air that gets in.

Now all I have to do is remove the two 3/4" through hulls currently in place, install a 1 1/2" through hull/sea cock, and replumb the entire livewell system. I hope this is worth it!

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Sea Chest

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