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Old 13-08-2014, 19:49   #1
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Do we Always Close the Exhaust Valve when Ocean Sailing

my new 33' steel yacht has a seacock / valve farback just before the exhaust exits through the stern. Meant to prevent seawater travelling back UP and into the engine , when sailing. Photo attached. Not that easy to get to: a tight squeeze for me - 6'4" 240lb. I have read of one instance where, after severe weather, the diesel had been badly damaged coz of water entering combustion chamber. Question? Do we all , as a matter of course " ALWAYS " shut such a valve when heading off soundings?
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Old 13-08-2014, 20:02   #2
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Re: do we always close the exhaust valve when Ocean sailing

How high does the exhaust hose rise from the seacock before it starts the slope down to the water lift muffler and is the exhaust riser/injection elbow below the waterline?

Whether you turn your seacock off all the time or just in steep following seas depends a lot on the design of your exhaust system. A big problem with flooding the engine is the anti-siphon valve between the heat exchanger and the injection elbow.

If the engine exhaust riser is below the waterline it may be wise to also turn off the water inlet seacock. Some people attach the keys to the seacock as a reminder to open it/them before you can start the engine.

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Old 13-08-2014, 20:10   #3
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Re: do we always close the exhaust valve when Ocean sailing

Mine gets closed EVERY TIME I turn off the engine.

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Old 13-08-2014, 20:14   #4
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Re: do we always close the exhaust valve when Ocean sailing

Panope, that is neat. I haven't seen one like that. Is it your invention?
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Old 13-08-2014, 20:30   #5
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Re: do we always close the exhaust valve when Ocean sailing

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Panope, that is neat. I haven't seen one like that. Is it your invention?
Yep. The flap is a scrap of Starboard and the counter weight is lead. I welded the "ears" to the boat during my rebuild and before the final painting. Easy peazy.

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Old 13-08-2014, 20:35   #6
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Re: do we always close the exhaust valve when Ocean sailing

Very nice.
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Old 13-08-2014, 20:37   #7
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Re: do we always close the exhaust valve when Ocean sailing

I am planning to add a drain to the wet box. If you don't know the boat its a good idea to close the valve for offshore but a well designed system shouldn't need it. Remember theirs still slot of water in the system that can cause problems. Nice system Panope
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Old 13-08-2014, 21:01   #8
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Re: do we always close the exhaust valve when Ocean sailing

Thanks Phil, Snowpetrel,

I made no attempt to create any kind of seal. I figure the flap will block better than 90% of the water volume and close to 100% of the water energy (wave). Water will have to travel about 18" upwards and about 4 feet forward in order to make it over the hump.

Someday, If I ever get in some decent following seas, I will open the drain valves of the water lift muffler and monitor the output. Only then will I know if the idea is really working or not.

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Old 14-08-2014, 03:22   #9
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Re: do we always close the exhaust valve when Ocean sailing

What about making a stick with two prongs to turn the valve from outside the locker?

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Old 14-08-2014, 04:23   #10
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Re: do we always close the exhaust valve when Ocean sailing

Maybe another approach is an anti-siphon loop on the exhaust

I would imagine a loop plus an exhaust flap would be more than sufficient

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Old 14-08-2014, 04:28   #11
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Re: do we always close the exhaust valve when Ocean sailing

Could also use a linear actuator to close the valve electrically, like this one, that way all you have to do is flip a switch
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Old 14-08-2014, 09:31   #12
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Re: do we always close the exhaust valve when Ocean sailing

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Yep. The flap is a scrap of Starboard and the counter weight is lead. I welded the "ears" to the boat during my rebuild and before the final painting. Easy peazy.

Steve
Really clever, Panope.

As for the original question, yes, if at all possible. You have a few options, however: a sort of flap that will stop all but a direct wave combined with a stern "squat" from letting much water in; an improved "gooseneck" to increase the height the water needs to rise to roll back down to the waterlift; an electric solenoid seacock to close this valve when the engine is switched off, or a mechanical linkage allowing you to close it and open it from some distance away by pushing and pulling on threaded rod or something. You could arguably use a Morse/Teleflex cable to do this as well. Of course, if you forget to open it and start the engine, things get ugly fast.
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Old 14-08-2014, 09:38   #13
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Re: do we always close the exhaust valve when Ocean sailing

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Originally Posted by Scare_Rab View Post
----
Question? Do we all , as a matter of course " ALWAYS " shut such a valve when heading off soundings?
The only thing "we all" on Cruisers Forum seem to agree on is to never be unanimous about anything.
I never shut my seacock when the boat is moving. It might prove embarrassing if I needed to crank the engine in a hurry.
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Old 14-08-2014, 09:47   #14
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Re: do we always close the exhaust valve when Ocean sailing

I have to say I've never shut an exhaust seacock in 40 years. I've had a few, but they were meant to be shut for survival conditions only. It is important to have a loop or something. I had one engine problem simply from little wavelets hitting the stern at the right angle while docked... gradually pumping water into the exhaust. I saved the engine but bent a pushrod on the aft cylinder when I started it.
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Old 14-08-2014, 19:02   #15
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Re: do we always close the exhaust valve when Ocean sailing

Got to be honest and say I normally don't bother on most boats. I did on one delivery because the system looked suspect and it was easy to reach. Hung the keys on the exhaust valve so as not to forget. I also closed the water intake on this boat. I wouldn't be supprised if 90% of the time water actually came in through the seacock, and a faulty vented loop.

You system seems good from the photo, nice high loop and 90 degree up just after the seacock. Does your engine have decompressors? If it does its a good habit to crank it over with the valves open to blow out any water and prelube the engine. Stops expensive damage if water has got into the engine for some reason.

Offshore engines only needed in calms and maybe for mob. So no great harm in taking extra precautions, specially if you are singlehanded. Inshore, best not to close it unless its really dodgy.
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