waterlock installation

[Bluefishboat]

I am about to re engine with a beta 1505, this may sound daft but the old perkins had no water lock, I have got a vetus LP 50 waterlock & want to fit it, the exhaust outlet in the transom is about 18" above the waterline, should the waterlock be installed above or below the waterline, or does it not matter
Ta for any advice

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[sailorman]

i have reciently changed a 4108 for the nanni 1505, u will have made a saving of £1100 ! .+plus a 2 yr unconditional warranty, unlike the crap warranty on the nanni.
the waterlock must be as low as possible & ought to be atleast the vetus NPL 50.
THE NANNI IS A BRILLIANT ENGINE, at the same revs (2800 ) as the 4108 i have had to increase the prop pitch 3" ( now 17 X 15 ) . cruises at 3lts per hr & better control in close quaters.

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[Jools_of_Top_Cat]

The waterlock should be lower that the exhaust outlet, low enough that gravity will move all water into the lock quickly, so as near to vertical below the engine exhaust outlet as possible, if the angle is not steep enough there is very little point in fitting the lock, it does not take a lot of water to kill the engine.

Think of your boat bobbing up and down, any water in the pipe between the exhaust and lock will be slopping about, the lower the lock the less chance of water backing up, while running there should not be a problem.

Think of the lock as a one way valve, you want a short run to the valve on the inlet side, to keep as little water as possible from having the chance to flow back into the exhaust. So if you can a quick drop.

As important as the water lock is an anti siphon on the inlet side of the water system, this will prevent the engine back filling when it is stopped. Why engine manufacturers do not fit these simple items to marine engines is ludicrous.


<hr width=100% size=1>Julian

<A target="_blank" HREF=http://www.topcatsail.co.uk/TC_IrishCruise_2003_00.html>Irish Cruise</A>

 

[vyv_cox]

\'Ludicrous\'

<<As important as the water lock is an anti siphon on the inlet side of the water system, this will prevent the engine back filling when it is stopped. Why engine manufacturers do not fit these simple items to marine engines is ludicrous.>>

Sorry, I totally disagree. How can water siphon past a positive displacement pump? The clearance required to allow this to happen is so large that the pump would not operate with it. The same applies so far as the siphon itself is concerned. Water cannot run back past the pump to break the siphon, it actually does the opposite, i.e. runs into the engine, the very condition it is there to prevent.

In cases where the top of the engine is lower than the water level, maybe when heeled, there might be a minor possibility of water seepage past the pump, although I doubt that this would ever be a problem and it certainly would not be siphoning. The siphon breaks that I am familiar with would not prevent this anyway, as water spills over the inverted U into the engine before it goes up the break.

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[SlowlyButSurely]

Re: \'Ludicrous\'

The anti-syphon vent goes on the outlet side before the water is injected into the exhaust.

Believe me this is essential if the engine is below the waterline. My engine was flooded once when the valve failed.

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[vyv_cox]

Re: \'Ludicrous\'

No problem with that. The post says on the inlet side. I have seen several installations like this and can never understand the logic.

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[brianrunyard]

Take a look at the Vetus catalogue.

<hr width=100% size=1>Brian
http://homepage.ntlworld.com/brunyard

 

[Jools_of_Top_Cat]

Re: \'Ludicrous\'

ok I see what I have wrote, and it is very ambigous, I mean the inlet side of the exhaust, I have mine fitted in place of the short rubber hose from the engine to the exhaust manifold. Yanmar 1GM10. It bleeds to an outlet on the hull.

I could not have a guarentee on the engines from Yanmar without these.

Sorry for any confusion, it was purely accidental.


<hr width=100% size=1>Julian

<A target="_blank" HREF=http://www.topcatsail.co.uk/TC_IrishCruise_2003_00.html>Irish Cruise</A>

 

[rich]

What have you done with the 4108?

<hr width=100% size=1>rich ) <A target="_blank" HREF=http://www.jersey-harbours.com>http://www.jersey-harbours.com</A>

 

[Bluefishboat]

Ta for all the info everybody, its been v helpful.
Have hopefully got a buyer for the 4107

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[HaraldS]

Re: \'Ludicrous\'

Have seen two positions of anti siphon loops in the sea water pass so far and both seem to work. The more usual is at the cooling water exit from the engine, before going into the elbow fitting, the other is right AFTER the sea water pump, before entering the engine.
In both cases they prevent water siphoning through a slighly damaged pump into an elbow that's below the waterline, where it would fill the water lock and then climb up the elbow and enter the engine at whatever cylinder has an open exhaust valve. Off course only if the manufold is below the water line.
Check valves in the anti siphon loop are a weak spot, they get stuck over time and nobody notices, until the day where an impeller gets bad and water leaks through the pump. Better is a thin hose from the loop top to outside or into the water lock. There will always be some water flowing from it when the engine runs, and I have seen people leading that little house into the cockpit (and out through the cockpit drain), as this is easy to install and you get a way of checking cooling water flow, all the time.
But most people who had flooded their engines, including my brother, had done so by filling the waterlook, cranking the engine for a long time while bleeding the fuel line. In that case the water lock slowly fills simply from the pump, and there is not enough air pressure to push it out, from just cranking. In such case one should always close the seacock of the water intake. (And open it quickly when the engine finally runs).



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[sailorman]

i also have a rebuilt t.m.p.hydraulic gear box + bell housing / flywheel to fit the 4107 /4108

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[MainlySteam]

Re: \'Ludicrous\'

I do not know why one anti siphon position should be regarded as superior to the other, from an anti- siphon point of view, as they are both in the same circuit and the only source of flow is from the seawater inlet seacock (assuming a correct exhaust installation).

However, the position straight after the raw water pump is definitely the best bet if one is not operating a tell tell off the siphon breaker. The closer the siphon breaker is placed to the water injection elbow in the exhaust the more chance that the valve on the top of the anti-siphon loop will leak water out as it then becomes exposed to the fluctuating pressure pulses in the exhaust. This position also has the advantage of having the break closer to the seacock thus protecting against siphoning on failure of any part of the system downstream of it, and which would allow ingress of water into the boat.

My own preference, all else being equal, is straight after the raw water pump.

John

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[vyv_cox]

Understood

Ah! now we are in agreement. I have a siphon break between engine and exhaust manifold, it feeds into the trap. I sometimes wonder whether this is logical or not, but since my exhaust outlet is very rarely below the water, and I have a high silencer loop, I doubt whether the siphon break can ever be in use anyway.

Responding to Harald's post, I cannot see how a siphon break in the pump-engine hose can ever be necessary, although as I said earlier, I have seen several fitted, in at least one case as a 'cure' for engine flooding. It would seem far more likely that the cause was over-use of the starter motor, as you describe.

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[MainlySteam]

Re: Understood

Vyv - I think there is a great deal of credence in what you say, in a circuit with a positive displacement pump in it (assuming it has not lost its vanes or something catastrophic) and typical sized hoses, I would not think a siphon break is normally going to add much to the security. If the engine is below the water line then it is, of course, mandatory to have a loop in the circuit going above the waterline to prevent straight through flooding through the engine or heat exchanger to the exhaust and water trap and hence back into the exhaust manifold of the engine.

However, for the point of where to put it ie after the raw water pump or just prior to the exhaust, I do not think it matters at all as it is all part of the same circuit from seacock to water trap. As in my earlier post though, if one has a siphon breaking valve on the top of the loop, rather than a straight connection discharging as a telltale outside the boat, then the position straight after the water pump has the advantage of the valve being less likely to dribble from the effect of the exhaust pulsations it would experience when located closer to the water spray into the exhaust.

John

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[HaraldS]

Re: Understood

Well, in such case the pump-engine hose is really much longer and lead up above the waterline and back down, with the siphon break mounted somewhere on the engine room wall. It does exactly the same as the installation between engine and elbow. On some newer engines I saw that the elbow was integrated with the engine block and no hose to break, then the only choice would be the aforementioned break after the pump.

Yes, the danger of inducing the problem yourself is higher, then the chance of a well maintained pump leaking and filling the engine with the starter is the most common problem. Though I know a case where the guy changed the impeller and damaged it slighly when squeezing it into the pump. So shortly after the test run, the engine filled with water. And yes, he had a loop, but one with a stuck checkvalve.

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[SlowlyButSurely]

Re: Understood

There's one final point: why on earth would anyone want to fit a Vetus waterlock? This is a failure just waiting to happen. If the Perkins worked OK without a waterlock why fit one now?

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[MainlySteam]

Re: Understood

I think we are all assuming that the engine is below the waterline - maybe it isn't in which case, as you say, why fit it?

John

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