[MediumRareBagel]

I also own a 38 Open but its a 2003 and have looked for the filter several times but have not been successful to date.. I contacted Tiara several years ago and they said its on the starboard side of the boat in the engine room close to the forward bulkhead and the hull. Above/around the hot water tank. Couldn't find it. Maybe you will have better luck.... Not sure if that's the source of the smell but I've been told the filter has to be replaced if liquid from the holding tank gets to the filter as a result of overflowing the holding tank. Where is the smell coming from, the engine room, the head itself, ?????

Found the filter directly in front of the starboard engine on our 2004 38 480-ce. Mounted horizontally.