Fuel Vent Line

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Bud Cary

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Jun 12, 2026, 2:33:48 PM (6 days ago) Jun 12
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Hi All

There are two vent outlets near the top of the transom on my J40

I'm looking to insert a dehumidifier in the fuel tank vent line and it's hard to follow where the it goes as it seems to wind around in the open transom area and in places I can't easily see or follow, but as far as I can tell it exits at the vent outlet on the starboard side of the transom. So my question is, is that correct (and generally standard on the J40)?  

As a note, my fuel tank is what I believe is the standard 33 gallon fuel tank located under the starboard side quarter berth but the vent line is initially routed over and under a water tank in the port side transom located behind the lazzarette.

The other question then is what is being vented out the outlet on the top of the port side transom as that hose disappears behind a bunch of stuff

Thanks

Bud
S/V Pooh (J40 #82)

Michael Murphy

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Jun 12, 2026, 3:04:56 PM (6 days ago) Jun 12
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Bud - on my J/40, hull #83, the starboard side vent is for fuel tank, and the port side vent is for the aft head holding tank, which on my boat sits in the cockpit locker (and likely yours tops since we’re just one hull number apart). 

I’ve seen/smelled them both in action, thankfully only very briefly on the fuel side. 
-Murph
J/40 Semper Quaerens
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Bud Cary

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Jun 12, 2026, 3:17:31 PM (6 days ago) Jun 12
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Murph

Great  Thanks for confirming

My holding tank is on the port side in the port side lazzarett but under and covered by a board to protect it from whatever is on top of it in the lazzarett 

Given the adjacency of our builds I may have some other questions for you as I learn my boat if that's ok

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