Diesel exaust problem

Re: Diesel exaust problem (KBT)

We used to use a tower separator with a dry exhaust feed. We cut the dry section and put in an exhaust elbow with injector and a changeover valve. Start the engine with water to the tower/separator (no backflow to the exhaust valves) and changeover to manifold injection once started, to avoid melting the exhaust hose. When stopping the engine, we switched over to the separator for a few seconds to blow all the water out of the first leg of the exhaust and then hit the stop. Works a treat!
Rob.
 
So the waterlock problem:

As far as I can see from all the replies on this thread, the ideal solution would be:

Turn the waterlock sideways 90deg. (I hope this doesn't affect its performance as it will operate heeled up to 15 deg.) then run the pipe as vertically upwards to under the side deck as possible (a total rise of some 30" at most, then down to the elbow at the back. The liquid volume aft of the waterlock will likely be just over 1 ltr in a run of 1.2m to the top. There is no syphon break at the moment, but would this be a good idea? And what would I need? Does all this sound feasible?
 
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There is no syphon break at the moment, but would this be a good idea?

[/ QUOTE ] It depends on the height of the water injection point into the exhaust relative to the waterline. You should have one if this is less than 6" above the w/l. If it is close to the w/l or below it you MUST have one.

It would normally be fitted in the pipework immediately before the injection point.

There are two types. One has an automatic valve that opens when necessary, but you must be sure to clean it periodically to be sure that it will open. The other has a continuous bleed of water that can go overboard or into a cockpit drain where you can see it. the advantage of this type is the at you are always aware if it is working or blocked. The down side of a continuous stream of water down a drain might be an increased frequency of micturition.

Again all is explained and illustrated in the Vetus catalogue. (except for the last point!)
 
Vic, the swannecks usually found near the end of the pipe are primarily to stop seawater coming back down the pipe when the engine isn't running. Only really necessary if the whole system inside it is either near or below the waterline. You are right in suggesting the swanneck can be placed straight after the watertrap, which in effect is what you achieve by going straight up and then have a long slope down. So long as the highest point of the pipe after the waterlock is well above the waterline when heeled there is no need to have anything else in the system.
 
Actually Vic, while again I agree with you, it is also necessary if the total volume of water retained in the waterlock and pipe when the engine is switched off is greater than the volume of water in the vertical pipe from the waterlock to the engine regardless of the height to the waterline.
The problem is that as the engine cools the tendancy is to suck water up from the waterlock to the manifold where it can enter the engine through the exhaust valve. If the volume of the vertical column in the pipe ( not the pipes total volume) is greater than the total volume of water still in the system, it can never get there and that's the only time an anti-syphon device is not required because if its a short pipe it can suck back the contents of the waterlock regardless of the waterline.
In other words fit an anti-syphon device to be sure. Like you I suspect, I favour the valveless type as there is nowt to go wrong. Valves jam and that's a pretty silly way to wreck an engine. Anti-syphon devices are easy to fit and personally I like to see them lead to a little 1/8 inch or less hull fitting near the exhaust outlet.
 
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The ideal solution would be turn the waterlock sideways

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I would think twice before doing this. The present location of your waterlock is good, ie low down. It is difficult to judge vertical height from the photograph, but your bilge appears to have considerable rise. This would mean raising the WL, perhaps significantly, if it you turned it sideways. If, as you say, you heel 15 degree on stb. tack, ( is that all ? ), a proportion of the contents may well run into the pipe between the WL and the engine. A bit of rolling in a seaway, and that water could slosh into the engine exhaust manifold. If you do go this way, I suggest that you consider a high-rise exhaust elbow to reduce this possibility. At least, do some measurements.t to assess the risk.
 
Well everyone, thanks for all the input so far.

Some further info:

Engine is a Beta 13.5hp

The exhaust manifold does actually have a high rise elbow level with the top of the engine, so at a guess that would give a 20" drop to the waterlock. As far as I can tell, the only thing you cannot see from the picture is the exhaust port in the counter is a further 18" aft, close to the waterline. There is no syphon break as far as I can tell, even at the counter end of the pipe so the whole pipe can flood at the moment, as far as I can tell.

I'm thinking of actually leaving the whole system as it is (well, re-installing it 'as is' after the rebuild. I think that if I chock the waterlock with one of the floors to the new tank, I'll have room for a 90ltr tank and not have to mess about with the pipe at all, which may be the best bet as I know it works!
 
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[ QUOTE ]
The ideal solution would be turn the waterlock sideways

[/ QUOTE ]
I would think twice before doing this. The present location of your waterlock is good, ie low down. It is difficult to judge vertical height from the photograph, but your bilge appears to have considerable rise. This would mean raising the WL, perhaps significantly, if it you turned it sideways. If, as you say, you heel 15 degree on stb. tack, ( is that all ? ), a proportion of the contents may well run into the pipe between the WL and the engine. A bit of rolling in a seaway, and that water could slosh into the engine exhaust manifold. If you do go this way, I suggest that you consider a high-rise exhaust elbow to reduce this possibility. At least, do some measurements.t to assess the risk.

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I agree that there is a lot of good, well meaning advice here.
Having a similar conundrum myself, (I want to change the exaust arrangement), but, having had water, in a big following sea, back into the cylinders, (on my previous boat), it is very easy to oversimplify the problem/risk.
The problem I had was too long a run from the water lock to the monkeys tail, big waves off Madiera slamming into the stern forced water up the exaust, 90hp Perkins.
Luckily I was wondering, could it!!!, checked and yes, it was hydrauliced.
I left the waterlock drain open on long passages ever after.
Sorry to ramble, just trying to make the point, that perhaps
it aint that simple!
 
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