Sevee,
The holding tank vent on the Mainship 400 comes out of the front of the tank (bow end). It's accessible from the small floor hatch in the V berth. It goes forward on a 90 degree fitting, then goes to starboard, then turns toward the stern under the floor of the bathroom, then goes behind the air conditioner, turns to starboard again, goes up the gunwale to the vent. Makes sense, huh?
I've never seen a more ineffective and poorly designed system.
Remove it all and run a vent forward, straight, no major bends, slightly uphill, 1" line, next to the anchor locker drain.
Here's a picture of what my 90 degree fitting looked like. PLUGGED! The picture doesn't show that it's totally plugged at the bottom. Really really smelled foul!
Jeffrey Guttenberger
R Time
2005 Mainship 400
View attachment 75597