Seacock Question

I have a 2001 Mainship 390. Can anyone tell me what the seacock in the well at the bottom of the steps supplies? It's right beside the sump pump that carries the shower and bath sink water overboard.
Thanks in advance,
Hawk

Seacock in 390

That seacock allows seawater to come into the electric head.

skipper724 said:

That seacock allows seawater to come into the electric head.

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Thank you!

I assumed the seacock under the engine on the starboard side went to the head.
ON my boat the starboard side has three seacocks, one for the muffler, one for the AC pump, and one I assumed went to the head. It has white hose attached to it.
Any idea what it supplies?

Thanks
Hawk

Have not seen a muffler that has a seacock supplying water to it. Maybe some sort of drain if it goes to the muffler.

May be an exhaust water separator for Genset to eliminate splash.


https://www.westmarine.com/buy/cent...laa1L_gx2wN-1a7GylieUOPIXDyQ_uCxoCu5cQAvD_BwE

Went to the boat yesterday and for some reason, that I don't understand, I have two seacocks that supply water to the head. One is slightly to the starboard side of the engine but almost under it and the other is under the cover at the bottom of the steps. the tee there and then it appears they go to the head. I am thinking the PO added it. It isn't bonded like all of the others. He also added a shut off at the head I don't understand. I am also interested to know why the boat has a supply line to the muffler.
Why would I have two supplies hoses/seacocks to the head?
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Hawk

If you care, as far as I can see.... none of them are true seacocks and slightly more dangerous than not having them true seacocks.

The one in the second picture is, as far as I can tell,, almost assuredly not, the upper one is harder to see completely. Neither is the one in the bottom pic.

If the bottom pic is the muffler, it may be an overflow drain line so the exhaust water doesn't back up into the engine. Assuming the muffler outlet is above the waterline.

Where exactly does the lower line connect to the head?

I think the upper one is original. I agree with you, the second one does not seem original. When I pull it I'll address that.
Thank you
Hawk

Original or not, seacocks are usually preferred over tnru-hulls with ball valves screwed on.

If the first and last picture have that set up, may want to think about replacing them at so m e point

psneeld said:

Original or not, seacocks are usually preferred over tnru-hulls with ball valves screwed on.

If the first and last picture have that set up, may want to think about replacing them at so m e point

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You are 100% correct. Many production boat builders used a straight threaded through hull with a straight nut to secure it.

That in and of itself was no problem until they connected a NPT ball valvt to the thing.

My boat has two of these and both will be replaced with regular pick your brand sea cocks next haulout.

Yes, the NPT and NPS threads do not work well together. Only a few threads will engage and the installation is suspect. Also through hulls are supposed to withstand 500 pounds sideways load for 30 seconds. It is likely that the install in the photos would not do that. I have no idea why there are 2 “seacocks” feeding the head. Sometimes you just can’t figure out the POs intentions. Just fix it and walk away shaking your head.

Comodave said:

Yes, the NPT and NPS threads do not work well together. Only a few threads will engage and the installation is suspect. Also through hulls are supposed to withstand 500 pounds sideways load for 30 seconds. It is likely that the install in the photos would not do that. I have no idea why there are 2 “seacocks” feeding the head. Sometimes you just can’t figure out the POs intentions. Just fix it and walk away shaking your head.

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Agreed, you also wonder why so many boat builders used the technique. Probably because a 1" ball valve is a lot cheaper than a 1" seacock, and costs add of.

OEM installation time would have been about the same.

Frankly I have not seen a production boat that used actual seacocks for anything other than the propulsion engines.

Probably the same reason people still use wire nuts.

90+ percent of them probably work for decades without mishap.....maybe failure but nothing serious.

Not saying it's the best way, but so many of TF posts are overly dramatic.

Sure, be safe do it the right way. I redid all my thru hulls when I bought my boat whether they needed it or not... but I also have enough experience that loosing your boat to a through hull failure ranks up there with being hit by lightning.

Psneeld, there is no shortage of scaremongers to be found on boating forums. My favorite "must-haves-just-in-case" are fuel polishing systems and dual Racor filter heads.

psneeld said:

Probably the same reason people still use wire nuts.

90+ percent of them probably work for decades without mishap.....maybe failure but nothing serious.

Not saying it's the best way, but so many of TF posts are overly dramatic.

Sure, be safe do it the right way. I redid all my thru hulls when I bought my boat whether they needed it or not... but I also have enough experience that loosing your boat to a through hull failure ranks up there with being hit by lightning.

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The head

On our 1997 390, that seacock next to the shower sump is for the seawater wash down hose outlet.

Duane Z said:

On our 1997 390, that seacock next to the shower sump is for the seawater wash down hose outlet.

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1997 was technically a 350. My 1999 350 has the head seacock right in the bilge space at the bottom of the stairs where the sump box is located. Technically, I think that is accessed inside of the door to the master.

In the OP's pictures, I also had the same quarter-turn plastic shut off behind the head (mine was red). The additional one looks like the OP's weird way of replacing hose and connecting (not sure why they didn't run a entire run.

The OP might has used that as a way to winterize the head.

What is the black tank?

Yep, meant to say 350, not 390. Our Vacuflush head uses fresh water, so it doesn’t have a seacock.

Duane Z said:

Yep, meant to say 350, not 390. Our Vacuflush head uses fresh water, so it doesn’t have a seacock.

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OP is using a Jabsco Electric Flush head. That is what was installed on my 350 and where the raw water was being drawn for.

I think I may know what happened. I know the precious owner liked to beach the boat on a sand bar because he had some glass a sand shoe onto the hull at the bow. I am guessing this caused a problem pulling fresh water from the original seacock so he added a second one in the engine room.
Always more to learn,
Thank you all.
Hawk

Agree with skipper724 - seacock in the well beside the sinks/shower gray water pump supplies water to the toilet. In my case, a Jabsco electric. In the 1st pic, that red handled ball valve must be a common supply to the toilet from either the original seacock or the engine room seacock, as you described. In the 2nd pic, the ball valve behind the toilet bowl allows water to the toilet bowl for flushing, and is the same as mine. The last pic looks like the muffler drain? Don't have that on our boat, so no clue. BTW, when moving our boat from Pensacola, after pumpout, to Gulf Shores on the first day of the 16 day passage up to our east Tennessee homeport, we discovered the holding tank was full to the vent. We had left the supply seacock open during this move and guessed the toilet internals were leaking by from the hydraulic pressure of the boat moving through the water, filling the holding tank. We pumped out the holding tank and kept the seacock shut the rest of the trip, unless we were using the head. Problem didn't recur. The red handled ball valve in 1st pic may have been installed for the same reason. With it shut, either or both supply seacocks could left open, and water wouldn't fill the holding tank while underway. Just a guess. I've got more troubleshooting to do on our head to solve that problem.

My 1997 350 came with that Thru hull/ball valve configuration from the factory. Every water supply is Thru hull/ball valve just different size to supply needs.