Exhaust hose shut off valve

P

PembrokeshirePromise

Well-Known Member
Joined
7 Mar 2005
Messages
844
Location
Pembrokeshire !
Visit site
Hi,

Would it be considered acceptable to install a shut off valve in the exhaust hose near to the engine (obviously after the water injection) rather than near to the hull fitting.

I realise by the hull fitting would be preferable - but access here means it wouldn't be used.

Was wondering about fitting just before (or after) the water lock - to prevent water being driven up the exhaust. If it is OK - is there any particular materials that will tolerate hot exhaust gases better ?

Thanks
 
An exhaust shut-off valve serves two purposes. The first is to protect the engine from flooding when following seas are climbing over your stern; a valve just downstream of the injection bend would serve that purpose OK.
BUT the second purpose is to protect the boat from flooding (and foundering!) when a heavy-weather sea blows the exhaust hose off the skin fitting, or splits a hose already degraded by age, rot, or overheating (because of raw-water pump failure; not uncommon?)
Every surveyor who has inspected my boat has checked the exhaust shut-off for integrity with the hull and for ease of closure. If it had failed on either count I'm sure he would have considered the boat unseaworthy.
 
Thanks for the answer.

My surveyor didn't seem fussed about this surprisingly - not even a recomendation! Exit is reasonably high above water level - but it would only take a few 100 gallons of water to lower the waterline to the point where it was at water level I guess

I guess I ought to look at improving access - currently behind a screwed on panel (lots of screws!) - but could be changed to something quicker to open I imagine - and then fit shut off valve where it should be.
 
Mine exits just above the waterline, (kind of under the sugar scoop type thing at the stern).... not seen anything which suggests there is a shut off, so I'm equally intereste to know if I should have one, or where it might be if I have one.

Cheers
 
Consider a flap outboard. Hinged at the top, with a tapered 'bung' that closely fits the outlet without jamming. Piece of studding through it with a small weight between two nuts so it can be adjusted to close the flap, to cope with a raked transom.
 
Sounds similar to mine.

I'm sure its been like that for the last 25 years or so - without apparent problem - but have just replaced the engine so am reviewing the exhaust system (hose of which has been much more recently replaced) at the same time.

I have a decent loop of exhaust pipe (comes up from exit to pretty much deck level before dropping down to exhaust muffler - volvo neoprene thing) - would have thought given the angle of exit and the loop of pipe it would take a lot to force water up in a following sea ...

Expect next question to involve mufflers and waterlocks /forums/images/graemlins/wink.gif
 
Good point - but I suppose on the positive it would have saved the engine (if it didn't all flow in as you tried to clear it ...)

Sounds like the only sensible and worthwhile place to have one is where it should be on the exit port.

Interested to hear I'm not the only one without - so clearly all surveyors don't consider it essential - or maybe it depends on how it exits ?
 
I used a steam one way valve for a generator that was suffereing from wave slap (blowing damp hot salty air back into the cylinders when valves were on overlap, after shut down.)on the ships side when not in use. Available from oakbray / industrial plumbers merchants etc. mounted as you discribe after the water mix point. advantage is cant forget to open it or close it.

its been in place now for 10 years and is still perfect.


ps it is bronze with stainless disc & closure spring.
 
I have one but never use it. My boat is pretty low on the water and the exit faces almost downwards. I think I get away with it because any flooding, following sea has to fight aginst the back pressure of air in the pipe to gain entry. The previous owner closed it and blew the head gaskets when he forgot and started the engine. The sort of automatic flap, often seen on fishing boats, seems a much better idea to me. With a cock for back up.
 
Just missed your reply, David. This sounds an idea with promise. Does the valve add much back pressure? Where could you obtain one (can't imagine it in the Compass catalogue)?
 
[ QUOTE ]
Interested to hear I'm not the only one without - so clearly all surveyors don't consider it essential - or maybe it depends on how it exits ?

[/ QUOTE ]I have no valve. The exhaust outlet is quite high on the transom with a substantial bronze fitting, and hose looped right up inside. A manual valve would be pretty inaccessible. Some sort of automatic one-way valve would be nice.
 
Obtainable from industrial plumbers Merchants

as to back pressure, virtually none, 1" head of water is sufficient to open it.
 
Further to the various posts about surveyors not very concerned about exhaust shut-off valves:--
A surveyor will assess a boat in relation to its designed/intended purpose and standard of construction: day-sailer, estuary cruiser, inshore/coastal racing, all-weather offshore passage-maker or ocean wanderer.
If a boat has basic design features which render it evidently unsuitable for offshore passages, a surveyor is unlikely to be critical of the absence of fittings for offshore duty. Bungs for all through-hull openings may be good enough.
 
Why use a shut off valve, why dont you use vetus gooseneck which is attached to the transom fitting and the exhaust hose is fitted to the top of the gooseneck fitting, which should stop the water getting back up the hose to the engine...
 
You must log in or register to reply here.

Other threads that may be of interest

T
Notices to Mariners - Week 50
Replies
2
Views
781
tillergirl
T

Share this page

Top