390 Propane Locker/Vent

Our 2002 Mainship 390 came equipped with a propane compartment located under the port side seat topsides. The compartment holds the gas solenoid valve controlled by the propane on/off switch in the galley. The lid has rotating locks (never have had the key for them).

Only the smallest Worthington 1 gal propane tank fits, with just a little clearance for the compartment lid. To clear the compartment lid the tank sits in a plastic "pan" about 2" deep in, the pan sits in a hole cut in the compartment floor with a lip on the pan with screws.

The pan has fitting mounted in the side that connects to a hose that would drain any LPG gas leaks. It isn't apparent where the other end of the vent hose exits the propane locker. Anybody know where this vents? I guess I could bring a compressor or use a tank to push air though it to try to find the exit.

Also, I think it is supposed to be a dry locker. There is no drain other than the vent line from the pan the tank sits in, and that is a little above the bottom of the tank, is when water gets in the tank just sits and rusts. The compartment lid came without any weather seal, so water gets in the compartment. I've just purchased two replacement tanks (the spare will store in a garden deck box I've put topsides behind the stair rail). It looks like the lid could accommodate a 3/16 weather strip, which I'm looking for to try to protect the new tank. I think the lid locks can be adjusted to provide tension to make a seal. I could add pictures.

You need air coming in at the top to allow the heavier propane to exit out the bottom drain. Sealing the top is counter productive to the design.

The Other Gary said:

You need air coming in at the top to allow the heavier propane to exit out the bottom drain. Sealing the top is counter productive to the design.

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Sorry, this is incorrect. The compartment is required to be sealed except for the drain.

ABYC standards for propane are written for worst case scenario. I can only assume they are concerned that the vent tube might get clogged and that the propane will fill up the compartment spilling into the boat if not in a sealed compartment.

That said I think there are many safe ways to store propane on a boat that don’t require sealed compartments. There are also many ways to do it wrong.

Sealed Lid

I wouldn't think sealing the lid would prevent escape of the heaver-than-air propane, assuming the reason for the gas is a leak filling the compartment.

I'm still trying to figure out where the hose vents.

Think I'll take my shop vac to the boat and see if blowing air in reveals the exit. (Heck, it's probably time to vacuum water out of the swim step...before the next haul I'll pull the lid and see if I can find the source - the trim tabs are gone and glassed over.)

As far as the lock goes, you don’t want to lock the compartment in case there is a leak you want to be able to access the tank without having to look for a key. Our RV basement compartments all lock except for the propane locker, it does not even have a key slot, just a mechanical latch.

jbbmillar said:

I wouldn't think sealing the lid would prevent escape of the heaver-than-air propane, assuming the reason for the gas is a leak filling the compartment.

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Liquid propane expands about 270:1 when it vaporizes, so a leak will simply push the gas out through the vent hose regardless of it's relative density, and that pressure would be miniscule unless the hose is clogged. Having the drain on the bottom would help if air leaks in and/or when the lid is opened.

Technically, the location the propane is placed is simply a seat locker. That is not a 'propane locker'. Propane lockers are sealed and vented. That space is simply vented. The question is, where is the seat locker vent routed? Where will the propane fall if there is a leak? The side decks below?

I need a sealed and vented proper propane locker like is being discussed here. 10 or 20 pound.

I would buy a reasonably priced new one or a used one if I could find one.

Any help on this? Sorry for the hijack.

Trident makes them but they aren’t cheap.

https://www.fisheriessupply.com/tri...fsMclVJMtJzvYLa4n9VLCCGS0np3xyjxoCV5YQAvD_BwE

Larry M said:

Trident makes them but they aren’t cheap.

https://www.fisheriessupply.com/tri...fsMclVJMtJzvYLa4n9VLCCGS0np3xyjxoCV5YQAvD_BwE

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I know and cannot think of a reason why a simple box should be that expensive.

The NT factory quoted me $1500 for one like what comes on a new boat.

When my boat was new it was ordered without a factory installed stove or oven...gas or electric. It was to be dealer installed. The now defunct dealer installed a propane Princess stove/oven but put the propane tank in a non sealed wall storage locker in the cockpit. When I bought the boat my surveyor said this did not meet ABYC guidelines so I removed the tank from the boat and have not used the stove/oven.

One of these days (when I sell) I am going to have to find an approved box or take it all out and put in an electric stove/oven. The plumbing for the propane locker is already there. I just need a box.

Topsides seat propane locker vent outlet?

I'm reluctant to trust but not verify that Mainship vented this compartment properly.

I tried to use my shop vac to find when the topsides seat locker used for propane vent outlet is. Using the blowing side I hoped to hear where air exited from the hose at the bottom of the compartment. The shop vac noise may have been too loud, but I didn't find the exit. I suppose I could try an electrician's snake.

jbbmillar said:

I'm reluctant to trust but not verify that Mainship vented this compartment properly.

I tried to use my shop vac to find when the topsides seat locker used for propane vent outlet is. Using the blowing side I hoped to hear where air exited from the hose at the bottom of the compartment. The shop vac noise may have been too loud, but I didn't find the exit. I suppose I could try an electrician's snake.

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What's wrong with a cup of water?...if it indeed is going over board...or not. You'll find out pretty quick.

You are going to freak when you find out it vents into your bilge. LOL

jbbmillar said:

Think I'll take my shop vac to the boat and see if blowing air in reveals the exit. (Heck, it's probably time to vacuum water out of the swim step...before the next haul I'll pull the lid and see if I can find the source - the trim tabs are gone and glassed over.)

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You might want to reconsider using the shop vac in proximity to LP/propane- or ANY flammable for that matter. Most use a motor with brushes that create an arc, the vacuum can mix air/fuel and the motor provides ignition..... you could be setting yourself up for a very nasty experience.

tiltrider1 said:

You are going to freak when you find out it vents into your bilge. LOL

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That's right up there with open the valve for a bit and throw in a match, looking for flames! Ouch!