Sweater or co detector? I use a $40 detector from amazon with a readout. The ones in the cabin are just on/off alarms.
Would suspect all you have to do is pressurize the cabin. Wouldn't take much I would think. It is done all the time with equipment and even autos that run in dirty environments. Their systems filter the incoming air but would not be required on a boat. Probably just a small blower. Is it possible the engines are causing a negative pressure in the cabin? Just a thought.
Do you get co in the cabin without the boat moving? If you do you have a exhaust leak, if you only get it when you are moving it's sucking it up because of the low pressure cabins. Just pressure up the inside just a little bit.
I would put all the side curtains up so it’d be nice and chilly, then ask the gal to lend me her sweater…….
Your comment made me switch things up a little. Previously, I had ran with the back flap and front vents open. Tonight, I left the back flap closed. Opened the front vents and took off. This kept my CO numbers at 0 for almost the entire night. Twice, they crept up to 35 but that is far less than what I used to see with that back flap open.
We run with the camper enclosure on a ton. When its nice out we will remove the aft panels. I have found that if I crack the forward windshield vent even slightly, I will not get spray or mist on the aft panels. I suspect the gas smell is a bit more pronounced than diesel but we don't even get a whif of it while underway.