Exhaust fumes in engine compartment

[amizerin]

HI there,

I believe this is one of the most asked questions but still want to ask

When engine is working the exhaust fumes are spreading into the engine compartment and the companion space. It's not that bad but still kind of unpleasant order.

When looking at the exhaust pipe and connections I cannot see any visible trace of fumes are leaking.

Might be it's ok that some fumes are escaping. Just want to understand when it's not ok and need repair.

[JOHN COOKSON]

HI there,

I believe this is one of the most asked questions but still want to ask

When engine is working the exhaust fumes are spreading into the engine compartment and the companion space. It's not that bad but still kind of unpleasant order.

When looking at the exhaust pipe and connections I cannot see any visible trace of fumes are leaking.

Might be it's ok that some fumes are escaping. Just want to understand when it's not ok and need repair.

NO IT IS NOT OK. CARBON MOXIDE IS A HAZARD. GOOGLE CARBON MOXIDE POISONING AND READ UP ON IT. GET YOUR EXHAUST SYSTEM FIXED!!!

ex TRUE GRIT

[tenders]

It isn't OK. If you're having difficulty finding the source, check the spark plugs. If they're loose, they'll leak exhaust gases.

A properly-contained exhaust situation means the cabin doesn't smell like exhaust AT ALL. A "hot engine" does not smell like exhaust.

[ndutton]

Are you sure you're smelling exhaust and not blow by?

[capnward]

+1 on not ok

Blow by is crankcase fumes, which are usually vented back in to the air intake of the engine. They are not as dangerous as exhaust fumes, but can contain exhaust if your piston rings are worn. If you can smell fumes, especially if you know they are exhaust, that's a red flag right there. Fix the exhaust leak, which, if your plugs are tight, is probably at the joint at the manifold end.
Then get a carbon monoxide alarm with a digital display, and place it where you live in the cabin. I have one of these: https://www.kidde.com/home-safety/en...kn-copp-b-lpm/
If it triggers, you have a problem. They are sensitive. Keep them away from solvent fumes. Study the instructions, and the risks at different CO concentrations. They will alarm sooner at higher CO concentrations. Check the readout of the CO level. CO has no smell, so the alarm can trigger before you smell any fumes. A CO level of 70 ppm sets them off after 2 to 4 hours. At that level you have exceeded the 50 ppm maximum recommended by OSHA for 8 hours of exposure. At 200 ppm, which could trigger the alarm after 10 minutes, you will get headaches and must get fresh air immediately. 3 hours at that level is life threatening. So don't hang out in the cabin until you ventilate it thoroughly.

[amizerin]

Thanks all for advice. I'm very aware of the risk of carbon monoxide poisoning. I'll install carbon monoxide sensor to see how bad it is.
It's probably blow by but I don't know how to tell the differerence. Will check all connections are right as well as plugs.

[Sam]

In meantime I hope you are periodically running your engine compartment exhaust fan... just to be safe while motoring.

[amizerin]

In meantime I hope you are periodically running your engine compartment exhaust fan... just to be safe while motoring.

Yes, I run my bilge blower every time I motor. My motoring is very minimal, just in and out the marina.

[amizerin]

I checked the exhaust pipe and found that water is dripping from one joint. I guess the fumes might escape from the same place.
I hanged CO2 alarm in the salon as recommended. It shows zero so far which is good. Tighten all plugs.

[edwardc]

If your exhaust is dripping water, chances are that it is corroded nearly all the way through, and is just waiting to fail catastrophically at the most inopportune moment. Since you can't effectively repair it, be proactive and rebuild the exhaust now. Unless its built from stainless, heat and saltwater mean that 5 years is about all you can expect from one.

Use black iron pipe from the Hardware store (DON'T use galvanized! Its toxic!!) and wrap it in thermal tape, sold here by our host.

Here's a link to the rebuild I did in stainless:

http://www.moyermarineforum.com/forums/album.php?albumid=73

Its now in its 10th year with no leakage.

[amizerin]

If your exhaust is dripping water, chances are that it is corroded nearly all the way through, and is just waiting to fail catastrophically at the most inopportune moment. Since you can't effectively repair it, be proactive and rebuild the exhaust now. Unless its built from stainless, heat and saltwater mean that 5 years is about all you can expect from one.

Use black iron pipe from the Hardware store (DON'T use galvanized! Its toxic!!) and wrap it in thermal tape, sold here by our host.

Here's a link to the rebuild I did in stainless:

http://www.moyermarineforum.com/forums/album.php?albumid=73

Its now in its 10th year with no leakage.

Thank you. It's most likely the time to install a brand new hot exhaust section. Seems to be not too complicated job except for unscrewing the old bolts that look rusty. I think I will have to take the manifold off and then work on the bolts.

When connecting the pipes and elbows what kind of sealer did you use? Obviously, plumbing tape won't work

[edwardc]

No sealer at all. Best to assemble it off the engine, as some force may be required to torque the fittings into the proper alignment with a tight fit.

As for the rusty flange bolts, go easy on them as they tend to break off. Patient application/reapplication of PBblaster, heat and tapping with a small hammer will help. Once they're out, replace them with stainless studs, stainless split lockwasher, and a stainless nut. This will resist corrosion better, and puts the operating threads outside the block, where you have easy access to them if it becomes necessary to cut/split the nut off.

[ndutton]

I used sealer when I replaced my hot section last year. That does not suggest it must be used but with toxic gases involved it was my preference in the interest of safety.

[joe_db]

FYI - if you pour some MMO into the air intake of a running engine, you will get thick oil smoke out of the exhaust. It makes leaks/holes pretty obvious

[amizerin]

FYI - if you pour some MMO into the air intake of a running engine, you will get thick oil smoke out of the exhaust. It makes leaks/holes pretty obvious

What is MMO?