webcraft
Well-Known Member
Who has a small (<30hp) auxiliary engine with an exhaust seacock fitted? Why should this be necessary?
- Nick
- Nick
Exhaust seacock - small yacht auxiliary
- Thread starter webcraft
- Start date
rogerthebodger
Well-Known Member
I am fitting seacocks to both the main engine and my water cooled generator as both exhausts exit out the side of my yacht.
I had a problem only when I put my previous yacht on the beach to clean the bottom when the tide came in the water came in the exhaust and I had to disconnect and block the exhaust to stop water getting in the engine. It also act to stop any one starting the engine to try to steal the yacht by motoring it away
I had a problem only when I put my previous yacht on the beach to clean the bottom when the tide came in the water came in the exhaust and I had to disconnect and block the exhaust to stop water getting in the engine. It also act to stop any one starting the engine to try to steal the yacht by motoring it away
Aja
Well-Known Member
Article in this months PBO where long term cruisers on Sunstone use this for their S&S40'. In a quartering sea they close the seacock to stop water being forced throuh into their engine.
Donald
Donald
Mirelle
N/A
I have one - 1.5" Blakes seacock on the 40mm exhaust hose of my ancient Volvo MD2 - and I use it religiously, although the exhaust exits under the counter and there is a good loop of pipe under the deck.
Since Blakes no longer make larger seacocks, I don't know what you do for a bigger engine. Ball valve maybe.
Since Blakes no longer make larger seacocks, I don't know what you do for a bigger engine. Ball valve maybe.
webcraft
Well-Known Member
OK, who doesn't have one fitted and why isn't it necessary?
Isn't this what a waterlock is meant to do?
-Nick
Isn't this what a waterlock is meant to do?
-Nick
colvic987
Well-Known Member
i dont have a seacock on the exhaust outlet, as i have got a swanneck on the exhaust pipe just before it exits the transom of the boat,
so no need for a seacock (in my opinion)
so no need for a seacock (in my opinion)
Phoenix of Hamble
Well-Known Member
I've got one, but never close it.... just ocassionally turn it to keep it from seizing..... its a large gate valve....
sailorman
Well-Known Member
fitted one to my Co 32 as she still had the original Yanmar YSE 12 ( flat single)
& prone to water entering the cylinder
& prone to water entering the cylinder
ean_p
Well-Known Member
I've a 2" high temp stainless ball valve for sale if you'd like to buy it......was intended for side fitted eberpacher exhaust but have now changed heater
regards
Ian p.
regards
Ian p.
Mirelle
N/A
No, the waterlock is intended to ensure that the exhaust is cooled and is accompanied along the hose by water. The swan neck is intended to keep water out of the engine.
Ships_Cat
Well-Known Member
Since Blakes no longer make larger seacocks, I don't know what you do for a bigger engine. Ball valve maybe.
In my experience usually use ss butterfly valves on big vrooom vroom type commercial MoBo engines and as such valves are available in smaller sizes same would be fine on smaller putt putt type engines.
For the thread, we have a 50 hp engine with exhaust out the transom and loop inside boat but no seacock - dunno as never measured it, but looped up probably 500mm or more above water line in around 75mm (from memory) PVC exhaust line from watertrap to discharge. Big Centek watertrap in exhaust so minor floods back not a problem (yet!).
In my view an exhaust seacock should not be necessary on a transom exiting exhaust and has the obvious advantage of not ever forgetting about it nor having to work out how to access it.
Construction rules for commercial vessels in some countries (including NZ) often infer such penetrations to the outside of the boat must be valved in case of loss of integrity of the interior pipework. But in my view on a small vessel it is easier to block the penetration from outside the transom with something temporary in such an event than to find ones way in under the cockpit or whatever to an isolating seacock.
John
In my experience usually use ss butterfly valves on big vrooom vroom type commercial MoBo engines and as such valves are available in smaller sizes same would be fine on smaller putt putt type engines.
For the thread, we have a 50 hp engine with exhaust out the transom and loop inside boat but no seacock - dunno as never measured it, but looped up probably 500mm or more above water line in around 75mm (from memory) PVC exhaust line from watertrap to discharge. Big Centek watertrap in exhaust so minor floods back not a problem (yet!).
In my view an exhaust seacock should not be necessary on a transom exiting exhaust and has the obvious advantage of not ever forgetting about it nor having to work out how to access it.
Construction rules for commercial vessels in some countries (including NZ) often infer such penetrations to the outside of the boat must be valved in case of loss of integrity of the interior pipework. But in my view on a small vessel it is easier to block the penetration from outside the transom with something temporary in such an event than to find ones way in under the cockpit or whatever to an isolating seacock.
John
webcraft
Well-Known Member
Thanks John,
That's what I thought.
Do you think there is any advantage in using a commercial swanneck (eg Vetus) over a simple loop in the exhaust hose? (Can't see it myself - unless you are a Vetus shareholder . . .)
- Nick
That's what I thought.
Do you think there is any advantage in using a commercial swanneck (eg Vetus) over a simple loop in the exhaust hose? (Can't see it myself - unless you are a Vetus shareholder . . .)
- Nick
Ships_Cat
Well-Known Member
Hi Nick
We just have a simple riser in the exhaust after the water trap and it is not vented at the top nor any special fitting there. From the water trap to the transom ours is actually done in rigid PVC (the grey stuff) and the up and down bits of pipe forming the loop are quite close together (as close together as the standard PVC elbows at the top will allow from memory).
I will be on the boat this afternoon our time and will measure up all the relative heights if you like and how they stack up against the waterline. This is in a 40 ft boat with 50hp engine so should just have to make allowance for that in that greater height is available for the loop but the exhaust is bigger dia so I would have thought more likely to flood back up the pipe from following waves.
If not already known, in doing it you have to consider the height from the water trap to the top of the loop as this represents a back pressure on the exhaust system through having to lift the water to that height. That height is dependant on the engine and exhaust dia, but the height of the loop above the waterline is normally said to be around 450 mm minimum for a transom exited exhaust.
I think ours may be a bit higher than that (from memory, but I will check) with quite a big lift from the trap to the top of the loop. However, I remember when we were sea trialling the boat there were periodically funny gurgling sounds coming from somewhere under the cockpit at times where the exhaust runs, when the engine had been running underway for a while. Unfortunately I was not there when the builder cured it and I never asked what was done but I suspect that the height of the loop may have been decreased with the gurgling noise having been the water trap getting full and the engine not being able to lift it the height up the loop (and I could see that the injectors had been pulled from the engine, maybe to check if any water had got that far back).
John
We just have a simple riser in the exhaust after the water trap and it is not vented at the top nor any special fitting there. From the water trap to the transom ours is actually done in rigid PVC (the grey stuff) and the up and down bits of pipe forming the loop are quite close together (as close together as the standard PVC elbows at the top will allow from memory).
I will be on the boat this afternoon our time and will measure up all the relative heights if you like and how they stack up against the waterline. This is in a 40 ft boat with 50hp engine so should just have to make allowance for that in that greater height is available for the loop but the exhaust is bigger dia so I would have thought more likely to flood back up the pipe from following waves.
If not already known, in doing it you have to consider the height from the water trap to the top of the loop as this represents a back pressure on the exhaust system through having to lift the water to that height. That height is dependant on the engine and exhaust dia, but the height of the loop above the waterline is normally said to be around 450 mm minimum for a transom exited exhaust.
I think ours may be a bit higher than that (from memory, but I will check) with quite a big lift from the trap to the top of the loop. However, I remember when we were sea trialling the boat there were periodically funny gurgling sounds coming from somewhere under the cockpit at times where the exhaust runs, when the engine had been running underway for a while. Unfortunately I was not there when the builder cured it and I never asked what was done but I suspect that the height of the loop may have been decreased with the gurgling noise having been the water trap getting full and the engine not being able to lift it the height up the loop (and I could see that the injectors had been pulled from the engine, maybe to check if any water had got that far back).
John
Ships_Cat
Well-Known Member
Hi Nick, these are the measurements.
Engine is 50HP, exhaust downstream of water lift muffler is run in 50mm grey PVC. Also there is no seacock.
The exhaust outlet out the transom is 350mm above the static waterline, there is then a horizontal run of approx 2m forward to the loop the rise in which is 535mm, so WL to top of loop is 885mm.
The top of the loop is just standard PVC fittings, being 2 off 45 degree bends each side to give a gentle 90 degree bend each side - the top horizontal bit is just a short bit of pipe so with the bends glued on the horizontal ends of the bends butt together (what getting at here is the two vertical parts of the loop are as close together as the fittings at the top will allow).
From the top of the loop there is a 1545mm drop down to the level of the bottom of the water lift muffler (aka as water trap) and the approximate rise back from the bottom of the muffler to the lower inside edge of the raw water injection point at the engine is 325mm (putting the lower inside edge of the injection point approx 335mm below the WL).
I think that gives enuff to sketch it out.
Also all the stuff I said in my last post about maybe the boatbuilder had to reduce the lift from our muffler to the top of the loop was rubbish /forums/images/graemlins/blush.gif - cos when I got the panelling off that covers it, it was obvious that the loop could never have been any higher than it is now (so I have no idea what he did to stop the gurgling sound /forums/images/graemlins/smile.gif.
Is blowing a gale here on board at the moment and heater is on /forums/images/graemlins/frown.gif
John
Engine is 50HP, exhaust downstream of water lift muffler is run in 50mm grey PVC. Also there is no seacock.
The exhaust outlet out the transom is 350mm above the static waterline, there is then a horizontal run of approx 2m forward to the loop the rise in which is 535mm, so WL to top of loop is 885mm.
The top of the loop is just standard PVC fittings, being 2 off 45 degree bends each side to give a gentle 90 degree bend each side - the top horizontal bit is just a short bit of pipe so with the bends glued on the horizontal ends of the bends butt together (what getting at here is the two vertical parts of the loop are as close together as the fittings at the top will allow).
From the top of the loop there is a 1545mm drop down to the level of the bottom of the water lift muffler (aka as water trap) and the approximate rise back from the bottom of the muffler to the lower inside edge of the raw water injection point at the engine is 325mm (putting the lower inside edge of the injection point approx 335mm below the WL).
I think that gives enuff to sketch it out.
Also all the stuff I said in my last post about maybe the boatbuilder had to reduce the lift from our muffler to the top of the loop was rubbish /forums/images/graemlins/blush.gif - cos when I got the panelling off that covers it, it was obvious that the loop could never have been any higher than it is now (so I have no idea what he did to stop the gurgling sound /forums/images/graemlins/smile.gif.
Is blowing a gale here on board at the moment and heater is on /forums/images/graemlins/frown.gif
John