Carbon minoxide detectors going off!

Marcdohc

Hello, I have a 2005 300 FV with twin Merc 5.0 mpi's. We usually travel at 24 mph with the front and side glass up as well as the front bimini. After around 10 or 15 minutes the CO detectors in the cabin go off. If I run the engine blowers full time, which im not comfortable doing they dont go off. Any suggestions?

MarkB

This happens on all of out boats. The problem is at speed there is a backdraft created that pushes exhaust fumes into the cabin. The fix is to have the windshield portal open, the portals in the cabin open, and cabin door closed. If you are still having an issue, and can depending on the wind, you should run your blower. It is not a problem to keep the blower running, in fact it introduces fresh air into the engine compartment and keeps the engine running cooler.

Capt Ron

Keep the cabin door closed during cruising and open up the center screen to get some airflow through the boat... that should help a lot. Running the blowers will only help the engine compartment and not the cabin or deck area. The gas is entering from engine exhaust through an effect called the station wagon effect. When you leave the back of the boat open and closed up the rest this effect takes place every time. You just need to crack a window open a bit in the front pf the boat and the station wagon effect will be lessen if not avoided entirely.

TonyWalker

This problem happens to us from time to time.  I was really surprised the first time it happened.  The cabin door was closed but enough found its way in to trigger the alarm.  I found an alarm at Wal-Mart that gives the levels on a read out at all times and triggers if the level rises to the perscribed threshhold.

If anyone is curious about how much CO there is in the garage when you run your car (garage door open)  take one of the detectors in the garage.  It will scream immediately.  I have it in mind to take the unit with the readout to the garage and make note of the levels.

Tony

Salt Shaker 342

TikiHut2

Station Wagon effect for sure. Can be deadly if not addressed. Numerous cases have been discussed by BoatUS and Seaworthy articles. For a little more on CO detectors there was a good thread on RBOC last spring found at this link ((HERE))

I have a similar CO det that has a readout and I held it back by the swim platform with the boat on a trailer to test it (while running on a water hose) and it didn't take 3sec to sniff a problem. I don't recall at what level it went off but it didn't take much. Rest assured it'd nearly wake the dead. I also placed it in the engine compartment  with the hatch down and the engine AND Genset running and thankfully got no CO leakage detected on the readout version nor my secondary basic house style detector.

Here's a label from a typical home CO det. These min levels are very high and Fire rescue personnel will be in full gear to enter a house at even the lowest levels listed here. I think their threshold is 40ppm for full gear. Your typical home device won't sound for 4hrs after reaching 150% of the EMS max level... Yikes
Be safe. Mike

Marcdohc

Hmmm, We run in some pretty rough seas from time to time, running with portholes and the center windshield open would make for a pretty wet ride. 

MarkB

Then I suggest closing back canvas up. You can open up the front canvas a little to get a breeze through. Should be high enough to avoid getting water in the boat.

Black_Diamond

Read the link to a thread on this from last year. Well worth your time: http://rinkerboats.vanillaforums.com/discussion/comment/7330/#Comment_7330

Marcdohc

How does the fumes get in the cabin? I keep the cabin door closed. 

Regarding ventilation in the cockpit, I usually unzip a side curtain 6" to allow air in. It does get pretty hot in the heat of the summer.

Capt Ron

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Marcdohc said:

How does the fumes get in the cabin? I keep the cabin door closed. 

Regarding ventilation in the cockpit, I usually unzip a side curtain 6" to allow air in. It does get pretty hot in the heat of the summer.

The cabin door is far from air tight. I had to add a foam seal around mine to keep the mosquitoes from coming in.

Black_Diamond

I know on my 342, the engine compartment is not sealed from the cabin.  Once you get the backdrafting going on, the CO will go everywhere.

TikiHut2

BD is right, There isn't a cabin door in any of these boats that'd seal tight enough to safely keep CO fumes out.

RY It'd take a huge effort with far more than just foam to seal that bulkhead, but in my opinion it should be done (although I haven't). The engine room bulkhead in my 270 has holes and gaps that a kid could crawl through which extend throughout the void between the liner and the hull from stem to stern on the port and starboard sides. I was shocked to think that in a worse case scenario raw gas fumes could infiltrate the entire boat as easily as having the engine right in the cabin and seek an ignition point far away from the higher rated motors/switches found in a typical engine room.

CO is a lot more insidious than raw gas and equally deadly, even for our diesel guys. Of course those cigars could be killin' you too...

MarkB

Yes, I have found the engine compartment is not sealed 100%, which is why running the blower prevents CO from building up in the cabin.

TikiHut2

Nothing quite like the smell of a diesel boat cabin and not much will prevent it once it migrates into the bilges under the floor and permeates the interior. It's just a part of the ambiance of most larger vessels.

CO on the hand is not eliminated as a crew hazard by simply running a blower. Even a tiny exhaust manifold leak can overwhelm a blowers ability to vacate the engine room of gases that can easily migrate throughout a cruising boat with a compromised/marginal fire wall/bulkhead......like many of us unfortunately (and often unknowingly) share.

This became a real concern of mine when I was looking at engine room fire suppression. Like RY I thought I'd just get a little foam to really seal off the compartment....... until I actually got the foam and went in head first to do the job. Yikes, I'd use up the better part of a half sheet of marine ply on that rear bulkhead with a hundred angles in at least 4 or 5 spots (most are now impossibly hard to reach with a screw gun, much less a caulking gun) along with all the trial cuts and control wiring/cables to even get close enough to use foam/caulk. All that said, if I was doing a major engine pull (or was 20yrs younger)  I'd make that bulkhead seal a high priority.

A properly sealed firewall/bulkhead would have made the original manufacturing a little more difficult but not impossible and would have most certainly made for a far safer vessel. Sadly, I'm sure it's no less than you'll find in any mass produced express cruiser.

CO migration above deck may be far easier to solve using the simple tips others have shared above. Be safe and keep those CO and smoke detectors well maintained for a healthy season ahead.
Mike

212rowboat

Re: exhaust leak

Pick up a can of seafoam from the auto parts store.. (gassers only, ry) :-)

Feed it into the intake manifold while the engines are running via vacuum.. pull an entire can in an engine.. once its infested, kill the engine.. let it sit for 20minutes.. refire engine and enjoy the smoke show.. look for smoke emitting from engine compartment instead of exhaust ports (hub) .. follow it to its source, and there is your exhaust leak..

Wanna see how much exhaust you draft while underway? Do the same thing, but instead of idling, motor down the drink and see how much (now visible) smoke drafts back into cockpit and cabin while underway... The seafoam makes it visible.

LaRea

BTW, on a 2005 boat, replace the CO detector if you haven't already. Typical service life is 5-7 years.  Check the "born on" date.