How to check exhaust leaks

[Mike53C]

Last weekend, when I got back at the marina and opened the door to the ER for my post arrival check, there was a slight, very slight haze and a strong, very strong smell. I told everyone to go out to the open, just in case and went back to turn on a fan so to help the extractors. Well about two hours later the smell was all over the place but I could not identify it. It is very sticky to the throat, made me almost sick, it is like burnt bakelite. It also remainded me of badly burnt gasoil. I assume it was not an exhaust leak since after two hours of blowing it should have cleared. I suspect an alternator, but I stuck the nose on them and could not detect anything. They charge ok too. When I got to the dock only the engines were working, no genset, no battery chargers.

But then this question started to trouble me....is there an easy, practical way to detect a leaking exhaust?

My motors are 12 71N.

Suggestions for possible cause of smell or leaking anyone?

Miguel

[Bob Bradley]

Do you have CO detectors to tell you if that gas is present?

[REBrueckner]

No one step, easy,foolproof check.

That smell of burned bakeite/phenolic resin is electrical in origin; either a mounting board or electrical insulation or both under heat attack. Not so often associated with burned out alternators in my experience...they tend to usually just blow a diode and stop working without much smell...If the smell was still strong after two hours of venting, it sounds like electrical and that the problem continued during venting.

A leaky exhaust would have the smell of exhaust fumes and or discharge raw water in most cases into the bilge. Different than the electrical smells. Any extra water in the bilge? or pumps running which normally don't?? Without raw water flow, various components might stink up the boat. But engine temp wouldn't likely be normal either.

You'll have to check via flashlight all nooks and crannies along the exhaust system ....with one engine at a time running ....for exhaust fumes...if tha's yourprimary suspect....if the smell is burned in nature,rather than just exhaust, the source will be around the engine risers and initial exhaust...or perhaps even your electrical panel...or other electrical accessories.

Until you find the problem, having fire extinguishers at the ready and even an extra one or two might not be a bad idea.

[SKYCHENEY]

I once had a very slight oil leak at the line going into the turbo. It made a huge stink but only after getting up to temperature. It did, however, smell like burnt oil. Once the line was tightened and everything cleaned up, the problem was solved. Since you don't have turbos, that can't be it, but maybe there is oil running onto an exhaust manifold. Look for evidence of oil leaks.

[Mike53C]

Do you have CO detectors to tell you if that gas is present?

No Bob, I don't, and this scares me now...maybe I will have to think of installing one.
Meanwhile keep talking guys, I am all ears....and writing down what to check next weekend.

Miguel

[doc g]

How about using a spray bottle filled with soapy water. Spray it on while the engines are spooled up ,so you have whatever pressure inside the exhaust system up . Look for bubbles. I would think you could find any leaks that way, unless the area was too hot and burning the soap/water off. I would think that first you need to decide if it's electrical or exhaust...........Pat

[Pascal]

well, it can be electrical, blowbyout the crankcase, exhaust gases or leaking oil burning off somewhere.

electrical burns are easy to recognize... cant' be mistaken.

how about a stuck starter ? did you try cranking ?

inspect everything, start one engine at a time to see if you see a leak or something...

[Genesis]

Burnt plastic is not exhaust. It is PROBABLY electrical.

Electrical fires are VERY UN GOOD. Find that problem!

[Beckytek]

Check your circuit breaker panel. I have had a breaker burn up and smell to high heaven. Some people thought an animal crawled in and died. Your nose is the best detector, now go around and sniff and you will find it. Ron

[Blaine Thorpe]

If you still suspect an exhaust leak, I have had better success watching the possible leak path areas while someone else starts the engine. It seems like the initial pressure change when the engine lights off causes the exhaust or soot to "blow" out of the leak path more so than just running the engine at an elevated idle.

If you spot something there should be some other tell tale traces of soot in that same area.

If you have a couple of people watching, you should be able to check each engine with two or three starts.

Hope this helps,

Blaine