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1995 Mariner 330 shower drain

Posted: August 1st, 2025, 11:20 am
by bogrumpus
Hello, we bought this boat several months ago and have done alot of upgrades/repairs and the last thing (for now) is the shower. Water flow in works great but I'm trying to learn the drain system before I use it. It has a switch for the pump on the main panel and also next to the shower. When both are on, the pump runs continuously. Looking down the drain, it appears to drain directly into the starboard bulkhead. From the center bilge access, I can see a hose coming in to the pump and back out through the bulkhead wall. From there, it's hard to see anything. I ran it for a little bit and the pump seems to run but all I hear is the occasional gurgle and slight intermittent trickle from what I'm fairly certain is the external mid-hull starboard drain port.
I plan to get a scope to look further but curious if anyone else has journeyed down this road? I searched the internet and found some info about some models with a sump and some with a float pump. No other obvious access to get under the shower. Anyone??

Re: 1995 Mariner 330 shower drain

Posted: August 1st, 2025, 4:43 pm
by buster53
Ok, most likely, water drains into a sump pump, not the bilge itself. Basically, you have a small plastic box, maybe 8 x 10 with a bilge pump inside. You access this box thru a bilge access port that usually will be located fairly close to the drain, maybe within 1 - 3’ and it most likely will not be in the head itself, but outside the door in the cabin area. Open up all access ports in the area to find it. My boat has several ports just outside the head (bathroom) door, but they are covered by carpet that just needs to be lifted.
You need to access the sump box from time to time just to clean it as it can get ugly inside of it.

Re: 1995 Mariner 330 shower drain

Posted: August 1st, 2025, 8:06 pm
by bogrumpus
That’s what I was hoping, but I think it is unfortunately draining directly into the bilge! Looking down with a pen light, all I can see is fiberglass. I ran the water for a little bit and sure enough the center bilge started to fill. The pump is running, but doesn’t appear to be doing anything so I have no idea where the hoses are connected to. I’m going to run a scope tomorrow to check but I think I’ll have to take the shower pan out and install a new sump and pump. Would love to know its history, but probably never will. Thanks!

Re: 1995 Mariner 330 shower drain

Posted: August 1st, 2025, 8:53 pm
by Midnightsun
If indeed there is a shower sump you will have access to it from a small panel under the floor most likely under the carpet. I will look something like this. https://defender.com/en_us/rule-automat ... box-system

These boxes are not sealed and if either the pump or limit switch fail, they will overflow into the bilge. They do get filled with soap scum and debris and do require regular cleaning once a year or 2 depending on how often the shower is used

Re: 1995 Mariner 330 shower drain

Posted: August 1st, 2025, 9:28 pm
by buster53
bogrumpus wrote:Source of the post That’s what I was hoping, but I think it is unfortunately draining directly into the bilge! Looking down with a pen light, all I can see is fiberglass. I ran the water for a little bit and sure enough the center bilge started to fill. The pump is running, but doesn’t appear to be doing anything so I have no idea where the hoses are connected to. I’m going to run a scope tomorrow to check but I think I’ll have to take the shower pan out and install a new sump and pump. Would love to know its history, but probably never will. Thanks!


You are turning a simple procedure into rocket science. I can almost guarantee you have bilge access ports in the cabin just outside the bathroom door. Pick up the carpet and look. All your hoses and probably your sump pump box will be inside one of those ports. Also, FWIW, Carver is well known for putting access ports in out of the way, out of sight places. Get a good flashlight and go hunting. I’ve had my 356 for 7 years and I just found a couple access ports a few weeks ago I had no idea they were there.

Re: 1995 Mariner 330 shower drain

Posted: August 1st, 2025, 9:44 pm
by buster53
Ok, did a little digging on the 330. No promises, but take a good long look at the inside of both your bath vanity and the cabinet underneath the main salon wet bar. Check the floor of each as one of them may have a removable, false floor that might give you access to the bilge.

Re: 1995 Mariner 330 shower drain

Posted: August 2nd, 2025, 10:43 am
by bogrumpus
Aha! In the very back of the wet bar cabinet (I looked before and totally missed it) there is indeed a 6 inch round port that gets me access under the shower. Unfortunately, there is indeed no sump anywhere or drain pipe/hose from the shower pan. Will never know the story of why they were removed but they’re simply not there! But now I have way easier access to put them in. Thanks for the last tip and digging a little :)

Re: 1995 Mariner 330 shower drain

Posted: August 2nd, 2025, 11:04 am
by bogrumpus
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Re: 1995 Mariner 330 shower drain

Posted: August 2nd, 2025, 11:07 am
by buster53
ok, another question for you...
I assume you have an AC unit. Where does the condensation drain to? It should be draining to a sump pump. I'm guessing it is just going into the bilge, but worth checking out.

Re: 1995 Mariner 330 shower drain

Posted: August 2nd, 2025, 11:23 am
by bogrumpus
It didn’t come with an AC unit. I took out an aftermarket propane heater and put in an electric heat pump and have it draining overboard.