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cp4000 · 08-28-2023, 01:38 PM

Hi everyone,
Went on a fishing trip last night and the carbon monoxide at the helm was very strong. I was cruising into the wind @20 MPH so not sure how it could be coming from the exhaust ports? It was so strong that my Carbon Monoxide detector went off inside my cabin. (I did have the companion way door open.) All exhaust tubes were replaced over the winter so I don't think there is any kind exhaust leak. I also noticed a strong smell when were trolling but that was just probably wind direction at trolling speed and exhaust coming up and over the side.
Any experience or thoughts on this? Don't want to risk anyone passing out on board.
Thanks as always,

Newbie7749 · 08-28-2023, 04:32 PM

(08-28-2023, 01:38 PM)cp4000 Wrote: Hi everyone,
Went on a fishing trip last night and the carbon monoxide at the helm was very strong. I was cruising into the wind @20 MPH so not sure how it could be coming from the exhaust ports? It was so strong that my Carbon Monoxide detector went off inside my cabin. (I did have the companion way door open.) All exhaust tubes were replaced over the winter so I don't think there is any kind exhaust leak. I also noticed a strong smell when were trolling but that was just probably wind direction at trolling speed and exhaust coming up and over the side.
Any experience or thoughts on this? Don't want to risk anyone passing out on board.
Thanks as always,

Was your canvas up? Do you have a generator? I would definitely re-check all of your exhaust ports and connections.

cp4000 · (This post was last modified: 08-28-2023, 10:20 PM by cp4000.)

Yes my bimini canvas was up and the center window was open?
Next time out I will lift the hatch and see if it smells down there. That should tell me if there is a leak or it is being sucked up over the sides. I did all exhaust work and doubt there could be a leak but who knows…
I wonder if it is like a vortex behind the boat sucking it back up on the deck over the transom?

And no genny…

hiccup · 08-29-2023, 07:48 AM

Gasoline engines generate much more CO when they are running rich than when the air/fuel is dialed in. I would suspect something is up with your engine(s) that is causing it to run rich.

With that said, the fact you were working on the exhaust system this offseason is a red flag as well. I don't understand the logic that because you had it all disassembled that it can't be the problem.

cp4000 · 08-30-2023, 12:24 PM

Thanks hiccup,
I'm not saying it can't be, just unlikely in my eyes as I am pretty meticulous in my work. I will recheck the hoses and clamps.
My engines do run rich, no question about that. I will work on that as well.
I was just curious if this was a common thing or something I needed to dig into further, sounds like I need to do some digging.

hiccup · 08-31-2023, 06:55 AM

Very unusual, and dangerous.

Running rich and recent exhaust work, I'd say you know where to start digging!

cp4000 · 09-05-2023, 08:59 AM

Update,
Checked over entire exhaust and re-tightened all exhaust hose clamps, nothing really jumped out.
Ran the boat at the dock for quite a while then lifted the floor hatch to see if a leak in the engine bay was present, nothing down there so have to assume it was probably coming up and over.
Took another group out for an 8 hour trip and not one sniff of exhaust the entire time.
I do think it may have been the weather conditions on that previous trip as well as the center windshield and door positions.
Will get carbs rebuilt in the off season and continue to monitor.
Thanks,

cp4000 · 06-09-2025, 10:19 AM

Update...
Installed new carbs, installed electric choke conversion kits and had the carbs adjusted by a pro. Much better but started getting that smell again. Think I finally got it! The 90 degree elbows just in front of the mufflers were sagging due to me climbing all over them running cabling from the radar arch among many other projects causing some small areas to open up and let fumes into the engine bay. I also noticed some winterizing coolant under the exhaust in that area this past Spring. (Self-induced after all) I cut out those hoses and installed a custom fitted 4x4 under the elbows for support and then replaced the hoses again.
Nice long 8 hour fishing trip this Saturday and all seems good...

hiccup · 06-10-2025, 07:45 AM

Make sure your flame arrestors are clean as well. Friend's boat was having a similar problem, and the solution was to ultrasonically clean the flame arrestors. Turned out they were absolutely filthy, although tough to see that before removing them. They were choking off air and causing a rich condition, bad exhaust smell and CO detector going off.