carbon monoxide goes off - could it be the flappers?

Brite Eyes

We took our boat for a trip and sure enough the alarm went off again even with all the isenglass in the back down and the front center off. It was very bad to the point captain on board was affected and friend on board passed out. Had to shutdown for awhile to recover. Luckily we had oxygen on board to help.
A friend mentioned to have the Flappers checked out on the engines (merc 350) as they had a similar problem. Had a mechanic check at dock but couldnt smell anything. Still waiting patient ly for our mechanics to come, but probably will be another 3 weeks so asking everyone to gain knowledge. I know I posted something similar a month ago but I apologize I cant find the post on my tablet. The captain sent an email to Randy then as well and Randy requested our number to discuss but we are still waiting for his call.

As you can imagine I'm not comfortable taking her out anymore and we really like cruising. Next trip scheduled to Baltimore and Annapolis and would hate to miss it.

Any other suggestions appreciated. 2008 350 cruiser

bat32

WOW!! A person who passed out from CO was in need of medical treatment ASAP.  Lucky for them to revive with no help. 

frodo13056

Another "WOW" from me - you are certainly very lucky. I recall your previous post and I mentioned that I have a CO monitor in my cockpit to ensure I don't have any CO issues like what you've had - not only while underway but also while at anchor or at the dock when folks are running their engines or generators. Something doesn't quite add up - your engines exhaust do not use "flappers" - unless someone modified the exhaust to exit thru the hull rather than out the lower units (it's not likely that your 2008 350 exhaust was modified). Most boats exhaust thru the lower unit into the water which creates a back pressure on the exhaust system because it it harder to push the exhaust out under the water. Many performance boats often have a thru hull exhaust system which pushes the exhaust out just above the water line which reduces the backpressure and in theory, provides a faster boat. The thru hull exhaust systems typically use "flappers" to allow exhaust to exit the hull but prevents water from backing up into the exhaust manifolds - basically the flappers act as a check valve to let exhaust out and keep water from entering. In your situation, as was mentioned before, you are most likely creating the "station wagon" effect where your exhaust is being sucked bak into your cockpit while underway. You did say that you had air flow thru the boat while underway but you did not mention if you were moving with a breeze or against the wind. If you were moving at say 20 mph and you have a 20 mph tailwind, then your airflow through the boat would be essentially zero since the tailwind would push air into the boat if you we're going any slower than the tailwind. It's possible that one (or more) of your exhaust manifolds or exhaust hoses are leaking exhaust into the engine compartment since the manifolds do corrode over time in saltwater environments and the exhaust hose clamps can loosen over time. If I was trying to troubleshoot this issue on my boat, I'd start off with checking the exhaust hoses and ring clamps and fix any problems found. then I'd be getting a decent CO monitor that has the digital readout. I'd then remove the canvas front, rear and side curtains then open the engine hatch, place the CO monitor in the engine compartment and start one engine, and wait a few minutes, shut that engine down and see if the CO reading went up and then do the same with the other engine. This would tell you if you have an exhaust leak in the engine compartment. Obviously, if you try this, you keep your head out of the engine compartment :-) Good luck and let us know what you find!

TikiHut2

That was a VERY close call and you're certainly right to halt all use of the boat until the issue is completely corrected. So glad that nobody was permanently injured. My guess is in line with Frodo. An exhaust leak perhaps combined with a major failure of the engine compartment firewall to prevent gas fume migration or as mentioned, following seas and wind during an extended run in the same direction.

I took the last CO post to heart and got serious about sealing the engine compartment and getting additional high quality CO monitor/detectors. I then put this Youtube video together two days before this very post to more easily show what I found. It seems eerily relevant to this most recent VERY close call.

(YOUTUBE LINK Pt1 and 2)

Man, That's a scary post. Hope others follow suit to see what they can do to prevent this from happening to them. Don't assume it won't happen to you. Check that firewall and update maintenance and warning systems as needed. Mike

Be safe, Mike

brianluck

glad everyone is ok, hope you can solve this issue! 

Black_Diamond

@TikiHut2: great video, the second one answered my question with my 342: huge openings past the firewall that would be impossible to block. I should have a CO monitor waiting for me at home to try out next weekend.

TonyWalker

Brite Eyes, That is really scary and extreme.  What ever it is, it should be a problem that is readily identifiable and correctable given its magnitude.  As this thread develops, we should all become more knowledgeable.  Tiki, that is one awesome video.

 

Tony

Salt Shaker 342

TikiHut2

Thanks guys. Hope the vid helps. After Brite Eyes story I'm not giving up on the firewall actually being one yet.

 I forgot to mention that I tested my new CO detector(s) by holding it at the stern while the engine was running and it quickly registered. So I figured I'd test my smoke(s) too. Pressed the test button and alarm sounded fine, and I don't know why but I thought I'd also try a real smoke test too......which it failed miserably. Out it went.

Double check everything....

212rowboat

Re: finding exhaust leaks...

Talk about tricky.. but, here is the best trick I've ever discovered, Fwiw..

Ever heard of seafoam? I don't care to discuss its merits as a cleaner or tuning compound, because "who knows". There is good and bad in that capacity.. if you allow it to siphon into the intake manifold via a vacuum port, it will draw fast enough to induct it, and slow enough not to kill the engine, or hydrolock it..

Once its all in there, kill the engine and allow it to rest for about ten minutes..

It will smoke like a Hollywood smoke machine when you refire it.. it will also smoke where the leak exists, if in fact there is one..

Brite Eyes

Thank you for all your suggestions and comments. The video was in lighten. Frido and tiki hut, we were traveling into the winds and seas only able to go 10knots so the station wagon affect could be happening. We did take down all canvas in the back as per previous recommendations. The captain and I took it out for about 4 miles and sure enough it went off again last week just to get a better understanding. Seems going up on plane and coming down off seemed to trigger the alarm. He ran the engines at the dock for a while and could not smell any exhaust.. As always once the problem is diagnosed and fixed ill report back so every one learns.

212rowboat

Some exhaust leaks only manifest under load and RPM, such as the case with stretched bolts that allow a float effect to happen.

mvn

Hmmm.. reminds me of the exhaust leak I found at the head/exhaust manifold gasket last summer. I couldn't smell anything but you could hear a louder than normal ticking sound.

BTW, there were flappers or shutters in my exhaust hoses past each riser (standard thru-drive exhaust).

Mark

Brite Eyes

We took your suggestion and bought a digital CO detector. Tested with port engine for ten minutes at the dock didnt register anything. Then tested stern engine it did register 30 and captain said didnt sound right. The last port on again and highest registered was 92. Engine hatch closed for each test. Next plan to test with more time in between each test and verify I reset the CO each time. Just sharing info for everyone's knowledge.

TikiHut2

Here's the link from the other CO post where @Bat32, being a fire fighter, commented that if readings are over 40ppm they'll enter the area with breathing devices. I think I'll also do what you've done and take my digital readout CO detector and lay it in the engine compartment to see what it reads in there with the engine running. If nothing else it'll be a benchmark.

Interesting update.  Mike

Former CO post (LINK)

212rowboat

Hold up..... Is that a catalyst engine?