Whilst the engine is out, I'm considering what to do with my exhaust. The system worked before taking the engine out, so it is a case of improving things for reliability and maintenance, rather than fixing things that are broken.

The black flexible exhaust ducts are in good condition, so I prefer to keep them. The elbow is full of calcium, but works, so I hope to keep that. I have an old Vetus water trap, that seems to work, but was full of black water and calcium flakes when I took it out (it sounded like a water-filled maraca when I shook it). I had heard that the Vetus water trap had been put in the wrong place or height, and it was certainly inaccessible and impossible to reach before I took out the engine. With the old arrangement, water was trapped in the ducts between the Vetus and outlet when the boat was at rest.

In summary, the old system looks like this;
Engine > Elbow > black flexible duct > Vetus water trap > black flexible duct > outlet.

Questions;
Should I replace the Vetus water trap? If so, with what?
Should I mount the water trap at a high level, so that water runs either to the outlet or to the engine?
Should I empty the water trap regularly, which means putting it somewhere that I can reach? I might have to route the exhaust duct through a cockpit locker to do this.

The photo shows the Vetus after removal of the engine, to the left of the shaft flange. You'll notice a big sag in the duct behind the P-bearing bracket, between the Vetus and outlet.

Drain the plastic bits and then fill them with a mixture of phosphoric acid [Metal Gleam}. Let that sit for a couple of days. Then drain and reinstall the whole set up. Perhaps replace the SS hose clamps.
Do not raise the height of the water muffler. The water is supposed to stay there and under no circumstance arrange it so the salt water runs back to the engine!

Hi Arch
Re your questions:
Should I replace the Vetus water trap? If so, with what?
Take it out and as Ramona has suggested clean the internals.
Then inspect the externals: plastics welds, throat fittings for exhaust in and out, base and sides for wear due to vibration.
If there is no apparent damage use it again. I have a feeling that if you price a new muffler you will see the merits of keeping the old one.

Should I mount the water trap at a high level, so that water runs either to the outlet or to the engine?
There will always be some water in the trap. This muffles the exhaust sound and cools the exhaust gases.
It seems to be in a good location. I can't see from the photo but it should be mounted so that it doesn't vibrate.
Usually there is a a rubber pad underneath and a strap around with rubber between the strap and muffler.
Having the muffler loose means that it can rub against something and eventually wear a hole.

Should I empty the water trap regularly, which means putting it somewhere that I can reach? I might have to route the exhaust duct through a cockpit locker to do this.
No need to empty the trap. As I mentioned, water in the trap is part of the cooling function and is always there.

You mention " black flexible exhaust ducts".
I take it that this exhaust hose. Quite expensive stuff but as long as there is water flow internally it last for ages.

All the best
gary

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Ramona said..
Drain the plastic bits and then fill them with a mixture of phosphoric acid [Metal Gleam}. Let that sit for a couple of days. Then drain and reinstall the whole set up. Perhaps replace the SS hose clamps.
Do not raise the height of the water muffler. The water is supposed to stay there and under no circumstance arrange it so the salt water runs back to the engine!

Thanks - especially about the height of the muffler.

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garymalmgren said..
Hi Arch
Re your questions:
Should I replace the Vetus water trap? If so, with what?
Take it out and as Ramona has suggested clean the internals.
Then inspect the externals: plastics welds, throat fittings for exhaust in and out, base and sides for wear due to vibration.
If there is no apparent damage use it again. I have a feeling that if you price a new muffler you will see the merits of keeping the old one.

Should I mount the water trap at a high level, so that water runs either to the outlet or to the engine?
There will always be some water in the trap. This muffles the exhaust sound and cools the exhaust gases.
It seems to be in a good location. I can't see from the photo but it should be mounted so that it doesn't vibrate.
Usually there is a a rubber pad underneath and a strap around with rubber between the strap and muffler.
Having the muffler loose means that it can rub against something and eventually wear a hole.

Should I empty the water trap regularly, which means putting it somewhere that I can reach? I might have to route the exhaust duct through a cockpit locker to do this.
No need to empty the trap. As I mentioned, water in the trap is part of the cooling function and is always there.

You mention " black flexible exhaust ducts".
I take it that this exhaust hose. Quite expensive stuff but as long as there is water flow internally it last for ages.

All the best
gary

Thanks Gary. In the current arrangement, the muffler is not secured, but just sits on the floor. The exhaust hoses are stiff enough to keep it there. I'l' consider a more secure arrangement (e.g. long cable ties secured to dead-eyes in the engine compartment), but take your point about possible chafing. The hose and clamps appear to be in good condition.

Here is the Vetus muffler/water trap, which appears in good condition. There is some lime scale left inside, but not enough to stop it working. I've got some phosphoric acid to soak it.

There is a small spigot with a small hole, about 1mm diameter at the bottom, below the outlet. See bottom right of photo. It had been blanked off with a rubber cap, which is next to the spigot (minus the corroded clamp). Is this a bleed hole, which would allow water in the muffler to drain while the engine is idle? My boat does not have a bilge pump, so it might have been blanked off to stop it bleeding into the bilge. Is it OK to blank off the small hole, or do I need to find a way to drain the water getting bled from it?

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Achernar said..
Here is the Vetus muffler/water trap, which appears in good condition. There is some lime scale left inside, but not enough to stop it working. I've got some phosphoric acid to soak it.

There is a small spigot with a small hole, about 1mm diameter at the bottom, below the outlet. See bottom right of photo. It had been blanked off with a rubber cap, which is next to the spigot (minus the corroded clamp). Is this a bleed hole, which would allow water in the muffler to drain while the engine is idle? My boat does not have a bilge pump, so it might have been blanked off to stop it bleeding into the bilge. Is it OK to blank off the small hole, or do I need to find a way to drain the water getting bled from it?

My only comment is how can your boat not have a bilge pump, a half decent pump and float switch are ridiculously cheap in the scheme of things and are, IMHO a very necessary safety item.

Just plug the muffler drain and leave it alone. You will need a bilge pump though. Start with a quality manual pump and if you think you need to add a 12v one do that later.

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Ramona said..
Just plug the muffler drain and leave it alone. You will need a bilge pump though. Start with a quality manual pump and if you think you need to add a 12v one do that later.

Plastic mufflers work until there is a raw water inlet restriction of any kind. Carry a spare.

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UncleBob said..

My only comment is how can your boat not have a bilge pump, a half decent pump and float switch are ridiculously cheap in the scheme of things and are, IMHO a very necessary safety item.

To clarify, I do have a bilge pump (and all the other Cat 5 Safety gear). It is a manual pump, not an electric, and it is not suited to draining small amounts of water that have been bled from a muffler. In any case, I would prefer not to bleed black, oily water into the bilge. Unless anyone can suggest a good reason not to do it, I'm re-sealing the small hole.