Silencer or water trap?

[pappaecho]

My trusty Perkins 4108, started leaking cooling water into the bilges. Suspected the 6 metre hose between the engine and the stern, but on trying to remove the hose, ended up with with a two part stainless steel device, which is about 1 metre from the exhaust elbow and much lower a good 600 mm than the exhaust elbow
It is basically like 7.5 litre paint can, with 50 mm inlet and outlet,on the top, and the bottom of the unit is now completely divorced from the cylinder due to corrosion, which is not bad as it is 28 years old!. The 50 mm inlet spigot is a pipe which goes down to the base of the unit approx 1 inch above the base plate.
The outlet 50mm spigot is simply welded to the top of the unit.
A chandler is trying to sell me a plastic replacement, which is described as a "water trap", but he also has in stock a "muffler" e.g. silencer.
Question is what is the function of the stainless effort now in kit form?
The 6 metre exhaust hose does a very large swan neck at the stern before it exits. All contributions appreciated

 

[Shanty]

Sounds like a water trap (or waterlock - same thing). I've a very similar "paint can" on my boat. These things are designed to collect any water remaining in the exhaust when the engine is stopped, and keep it out of the engine. It will also act as a silencer to reduce the exhaust noise from the engine.

You can also buy a muffler that just serves to reduce the noise.

What you want is a waterlock - made in plastic by Vetus, or in fiberglass by Halyard Marine. The size you need will depend on the diameter of your exhaust hose, and the length of hose - long hose, bigger waterlock.

Hope this helps

 

[Guest]

The idea of the water trap is that the exhaust from the engine (with the water injected) is put into the top of the box. The outlet end is from the bottom of the "paint can". Water accumulates in the trap/pipe until the pressure gets high enough to expel it through the transom. Hence the splush splush of a yacht exhaust.

You said the inlet spigot goes down to the base of the unit. This seems to be the wrong way around. If you look at the vetus site for the 30-90mm water traps the picture at the start shows the "in" going to the top of the box and the "out" coming from the bottom.

The only problem with a plastic one is that you do not get much time between the cooling water failing and the plastic melting due to the exhaust temperature.

 

[philip_stevens]

The Vetus NLP waterlock would be similar to your metal "silencer". I have one on my boat, and have found no fault with it.

I think the previous poster was wrong in saying the water went in at the top and out at the bottom. If you look at the link, you will see in at bottom, out at top.

The good thing about this model, is that it will fit into a small space, and rotate to different angles.

A 50mm (mid range) price from ASAP-Supplies would be in the region of £81 +VAT - or less if you have an account.

 

[pappaecho]

Thanks for all your replies.
Have looked at the Vetus watertraps, which would be fine if they fitted into the engine compartment. I have taken the decision to get a local stainless fabricator to make a direct replacement, as the cost would be about 1.5 times the cost ofa plastic one, but when all is said and done the last one in stainless lasted 28 years

 

[Guest]

philip_stevens: If you look at your own vetus reference you will see that it is a double trap unit and that the "in" is actually the top of the lower unit and the "out" is the bottom of the higher compartment.

The central tube goes from the bottom of the lower trap to the top of the upper trap.

So in general for a single "paint can" trap (with both tubes going through the top of the can) the "in" is definitely the short pipe and the "out" is the long pipe that goes to the bottom of the can.

 

[philip_stevens]

Confusing!

Even if it is a double trap, the water goes in the bottom trap and out the top. The lower trap inlet is lower than the top outlet. So, in the lower, and out the upper.

 

[alldownwind]

If the corrosion is confined to the bottom of the unit, you might be able to get away with having a new base welded on? This is exactly what I just had done on our Moody, same problem. £25 to fix at a local metal-work shop.

 

[rogerthebodger]

Have a look at these exhaust water lock. These are the most common used and the inlet is at the top and the outlet at the bottom
http://www.vetus.nl/producten/mainns.asp?productid=9&lang=2

 

[Guest]

In - Out .... Top - bottom .... love it !!

I have a straight large bore pipe from manifold to transom and no muffler or water-lock ... on a 4-107.

Don't have to worry about in at bottom / top or anything ....

Love it !!

/forums/images/graemlins/grin.gif

 

[TheBoatman]

Re: In - Out .... Top - bottom .... love it !!

Nige
Trust you to have a "straight throu'"

Noisy bu***r /forums/images/graemlins/smile.gif

Peter.

 

[Guest]

Re: In - Out .... Top - bottom .... love it !!

Its not that noisy outside actually ...

I do think about it occasionally to fit something .... but the Scania Truck exhaust I found in the skip was too big !!

/forums/images/graemlins/grin.gif

 

[philip_stevens]

Yes - I can see what you are looking at, but if you read the original post, he is describing a unit that would resemble (a 7.5 ltr paint tin) the Vetus NLP watertrap - as my post showed! His went in the bottom and came out the top - or so it sounded to me.

I repeat - with the NLP, the exhaust goes in the bottom chamber and comes out the top chamber.

Anyway, he is going to get his original repaired.