I noticed the other day that there was negative air pressure in my engine rooms: the door felt like it was a tiny bit sticky when I opened it. The previous owner had built and installed an assembly to hold blue HVAC roll filter material to screen the top and side of the air inlet in the hull. We have been running for the past two years and almost 1000hrs on the existing filter medium, so I guess it was due.

I removed the filter housings and pulled off the old elements, they are just over 6’ long and the top was 14” wide and the onboard face was 10”. I got a roll of 1” filter material from the local HVAC supply house and swapped out the dirty old material. The old was still transmitting light, but was black and dusty on the side facing outboard while the new was bright blue and translucent. A quick start and run up of the engine on that side showed no lowered air pressure. The door swings open of its own accord while the engine is running now. It would not do so before.

I am guessing that these filters are one reason my Walker AirSeps stay clean and bright red from one year to the next and why I never have any dust in my engine room. I’m sure that this is a homemade assembly since there is no makers name on it. I still have to do the starboard side so if anyone wants pictures, I can take them tomorrow. A 36”x30’ roll was $100, Grainger has it in 1/2” and 1” for much less, but we are only here for a few more days.