Seacock on engine exhaust

[Stemar]

A motorboat I used to work on had a flap on the exhaust fitting, a bit like the kind of thing you get on top of a tractor exhaust. When burbling at idle it made a pleasant soft "clang clang" noise. I've never seen one fitted to a yacht, is there a reason it wouldn't work?

I have one on Jissel. The flap is rubber, and the exhaust pressure has left it with a permanent bend, so it's always a bit open, but I reckon a slap from a wave would close it.

Personally, I wouldn't want a valve on the exhaust. I'd think, "I'm going to be sailing for the next 17 hours across the channel, and I've got the wind behind me, so I'll close it." Then dozy me would realise that big bugger seems to have forgotten the bit in the Colregs about giving way to vessels under sail and start the engine to dodge. "Oh *@%~@+, the engine's died. Now what?" An automatic one would be great until a bit of salt water finds its way into the connections, then I'm even less likely to realise what's gone wrong because it never did before, and the symptoms of a blocked exhaust would be very similar to a fuel supply problem.

 

[rogerthebodger]

I have one on Jissel. The flap is rubber, and the exhaust pressure has left it with a permanent bend, so it's always a bit open, but I reckon a slap from a wave would close it.

Personally, I wouldn't want a valve on the exhaust. I'd think, "I'm going to be sailing for the next 17 hours across the channel, and I've got the wind behind me, so I'll close it." Then dozy me would realise that big bugger seems to have forgotten the bit in the Colregs about giving way to vessels under sail and start the engine to dodge. "Oh *@%~@+, the engine's died. Now what?" An automatic one would be great until a bit of salt water finds its way into the connections, then I'm even less likely to realise what's gone wrong because it never did before, and the symptoms of a blocked exhaust would be very similar to a fuel supply problem.

Simple you fit a micro switch to prevent statrtng the engine with the seacack closed just like a start in gear switch that prevents starting the engine while in gear.

The only problem is that you forget the engine is in gear and then panic when the engine wont start so you the fit an alarm to sound when you try to start the engine in gear of seacock closed.

Please don't ask how I know all of this.

A seacock in the exhaust is a great anti theft device.

 

[peter gibbs]

You will have noticed that RNLI boats have these SS flaps on the exhaust ports and they are beefy preventers. I guess pilot boats too. Given their engines are in service at all times at sea you might think them superfluous - apparently a fully prepared vessel requires them, and not to prevent birds nesting! Food for thought.

PWG

 

[peter gibbs]

You will have noticed that RNLI boats have these SS flaps on the exhaust ports and they are beefy preventers. I guess pilot boats too. Given their engines are in service at all times at sea you might think them superfluous - apparently a fully prepared vessel requires them, and not to prevent birds nesting! Food for thought.

PWG

Further to the above, I note a check value fitted exhaust outlet offered in the Force Four chandlery catalogue (2019 edn) at about £30 with 3 sizes - 40/45/50 mm.
Cat no 830785 - 0089 etc. No personal connection to the retailer.

PWG