Sealine S240 engine fumes

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SLVUK

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I have a Sealine S240 senator, lovely boat well cared for but I have an issue regarding fumes when the engine is running. She has a 4.3 Mercruiser EFi in excellent order. So, when I run the engine and cruise at 5-10 knots, after a while the Co2 alarm will go off in the cabin unless the hatch is open? I'm wondering if anyone else has had a similar issue and wondered if it was leaking through the engine bulkhead maybe? Is this something other similar cuisers suffer from? Iwould appreciate any advice. Many thanks in advance.
 
That sounds bad, on the face of it. There shouldn't be excess fumes on the other side of the engine bulkhead either. I think in that situation I would check over the entire exhaust system very carefully in case there is a split or loose joint.

Even when the exhaust is working properly there definitely can be a problem with exhausts and tailwinds but because you say "unless the hatch is open" it doesn't sound like that.
 
Are you running with the front section of canopy up? Sounds like you are getting a vortex effect putting the exhaust fumes forward, very common. Drop the canopy and see what happens.

Extremely unlikely to be fumes leaking through the cabin bulkhead because it's exhaust fumes setting off the alarm and those fumes should be going through the exhaust manifold into the exhaust and out of the outdrive, not into the engine space (where they would need to be to then leak through a leaking bulkhead).
 
Just to add, hopefully you are running your engine space blowers (fans)? You absolutely need to for a good few mins before starting the engine and whilst the engine is running, which is another reason it is very unlikely to be fumes from within the engine space as the blowers should be keeping it clear.

The main reason for the blowers is to clear any petrol vapours from the engine space which are, of course, explosive. Petrol boats have blown up in the past due to engine space blowers not being used.

Worth checking also that they are working (with the engine hatch open and the engine off, you should be able to hear them running very clearly).
 
And finally - if you are running with canopies up, put a Co alarm (it's carbon monoxide, not carbon dioxide which is Co2 - a common mistake) in the cockpit because if it's setting the cabin alarm off from fumes pulled forward from the exhaust, I dread to think what the levels in the cockpit - which it needs to pass through first - are like!
 
ari said:
Are you running with the front section of canopy up? Sounds like you are getting a vortex effect putting the exhaust fumes forward, very common. Drop the canopy and see what happens.

Extremely unlikely to be fumes leaking through the cabin bulkhead because it's exhaust fumes setting off the alarm and those fumes should be going through the exhaust manifold into the exhaust and out of the outdrive, not into the engine space (where they would need to be to then leak through a leaking bulkhead).
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The Sealine 240 / S24 bathing platform set-up can cause fumes to enter the boat from the outdrive exhaust, particularly if the wind is in the "wrong" direction...
-The cockpit drains are under the bathing platform and if the engine hatch rubber seal is old, fumes will enter the engine bay and also the cockpit (which has no seal)
-The Bathing Platform ladder has a blower vent into the engine bay, another possible source if the blower is not switched on!

I would say it is critical to have a CO alarm fitted in the cockpit low by the helm seat in addition to the cabin CO alarm.

The engine bay bulkhead is reasonably sealed off to the cabin, therefore if your CO alarm is going off in the cabin I would be very very concerned. To me this would indicate an issue with fumes leaking directly from the engine exhaust system in the engine bay and not from outside.
 
What ari says ! I had a searay 240 and we ran inland channels and hull speeds with just the rear canopy open and tailwind . After an hour the co detector went off .

Never had an issue with canopy fully open or fully closed
 
aerobat said:
What ari says ! I had a searay 240 and we ran inland channels and hull speeds with just the rear canopy open and tailwind . After an hour the co detector went off .

Never had an issue with canopy fully open or fully closed
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The Sealine manual has warning of just that, a risk for any canvas boat.
 
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