CO2 issues

[SeaBassBill]

Hello, I am new to this forum but wanted to see if anyone else has this problem / fix.
I have twin Volvo/Penta 5.0 in a 2007 Four Winns 318 Vista, they run fine and sound like new.
After I return to the dock I run the blowers at least an hour, usually about 5 hours later my CO2 monitors start going off, it's not the monitors that came with the boat, it's a plug in that reads the ppm and 2 others that just go off when CO2 is present at a specific level. I run the blowers again, stick a fan in the door blowing out and sometimes run the exhaust fan in the head. This continues about every 2 hours until the next day. The CO2 level never reads above 90 or so but enough to have me worried and keeps me up. I know there must be a leak but it's not evident where. Any thoughts?

 

[alldodge]

Welcome
If its in the bilge then sounds like gas fume monitor and not a CO detector

If gas fume then can you smell gas?

 

[tpenfield]

Wondering why you are running the blowers for an hour after you return to the dock? Is there an issue we are not hearing about?

CO2 monitor would be in the cabin and a fume detector would be in the engine bay/bilge.

Assuming it is the CO2 . . . then you probably have an exhaust leak. Salt water or fresh water?

Got any pictures to share?

 

[tpenfield]

FWIW - I had an issue with the exhaust 'down elbows' on my Mercruiser 7.4 (I know you have a V-P, but could be a similar situation). Saltwater took its toll on the aluminum exhaust duct.
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There was a faint exhaust smell whenever I checked the engine bay while the engines were running, but I did not track it down until I did some work on the exhaust manifolds. However the CO2 alarm never went off. Your issue may be more severe.

So, have a good look at your exhaust . . . the clamps, rubber couplers, and the various elbows/pipes.