[Anonymous]

I have found a very slow leak in our exhaust water trap (Volvo MD2020 on B32)… it appears to be a tiny hole somewhere around the outlet weld…. I guess it is a pretty corrosive environment! Now to the question… has anyone tried replacing the standard part with an alternative (e.g. Veteus)?

[Anonymous]

I’ve had exactly the same problem with the exhaust on ‘Another Fantasy’ (B32 Volvo 2020). I looked into fitting a Vetus GRP silencer/water trap but it eventually fell into the ‘too difficult’ box; in particular the exhaust inlet and outlets were incompatible. My solution has been to have new end caps fabricated, with more substantial welding around the inlet and outlet fittings. The fabrictor felt that part of the problem is caused by galvanic corrosion, so he fitted some threaded studding to the end caps, which I’ve connected to the hull anode.

I’ll let you know how things progress. So far so good, with no re-appearance of the pinholes…..

Ian Culley

[Anonymous]

Ian can you post up details of who you used and approx cost?

Thanks

[Anonymous]

@another fantasy wrote:

The fabrictor felt that part of the problem is caused by galvanic corrosion, so he fitted some threaded studding to the end caps, which I’ve connected to the hull anode.

I’ll let you know how things progress. So far so good, with no re-appearance of the pinholes…..

Ian Culley

Ian

I’m not sure connecting the end caps (inside the engine compartment?) to the hull anode (outside in the sea) will have any effect on galvanic corrosion of the end caps. AFAIK the anode must be able to ‘see’ the metal it is protecting through the electrolyte i.e. literally line of sight.

I think any corrosion experienced is more likely to be simple chemical corrosion. Hot seawater is highly corrosive, especially when propelled by very hot exhaust gases.

If the corrosion is partly galvanic then an anode internally attached to the end caps might have some positive (no pun!) impact. However, it would probably suffer quickly from chemical corrosion in such an environment.

Roger

[Anonymous]

I agree with Roger that I think the anode needs to be located close and in the same electrolyte rather than just bonded. If not I would be able to just have one anode attached to the bottom of the swim platform and make checking and replacement easier.

I don’t know of any suppliers in the marine environment but we did used to get the race car exhausts coated internally with an epoxy paint to help with gas flow, perhaps coating the water trap internally with epoxy resin may offer some protection from corrosion. It might be worth looking into the costs of an epoxy coating at some point.

Paul

[Anonymous]

Roger/Paul

Many thanks for your constructive feedback on this problem. To be frank I was very sceptical of the ‘galvanic corrosion’ theory put forward by the engineer for precisely the reasons that you’ve both put forward (i e electrode ‘line of sight’ and both electrodes needing to be in a common electrolyte). However I thought that there would be nothing to lose by giving his suggestion a try, even though I think that chemical corrosion is a much more likely cause. Having said that, if you think about it there is the potential (another pun….) for some galvanic corrosion in the silencer box, with differing metals in the end cap assemblies in contact with a fairly corrosive cocktail of exhaust gas and seawater.

I’m surprised that the problem of end cap corrosion hasn’t been more common. I’ve had to replace the exhaust elbow on Another Fantasy because of corrosion, as well as dealing with the leaky silencer. There are two issues, the inconvenient one of leaks and water in the bilge but a more serious risk from carbon monoxide leaking into the interior cabins. When I first noticed the leaky silencer I installed a CO monitor which so far hasn’t gone off in anger, so presumably if there is any CO leakage it’s at very low concentration.

For ‘Amaretto’s’ benefit the engineer I used at Chichester Marina is Andy Parham, e-mail seaworthyservices@btinternet.com, mobile no. 07834 764528. He’s very helpful.

Ian Culley

[Anonymous]

I have effected a temporary repair around the outlet weld so hopefully we can hold off until the end of the season before sorting out a replacement.

It looks like T. Norris may have a suitable replacement (http://www.tnorrismarine.co.uk/exhausts.php, HEE model, part number H001498 or HEE020). I will try confirm this with them before having to buy though!

[Anonymous]

Well we have finally got around to removing the old muffler/water-trap. Unfortunately its beyond welding repair.
We decided that it would be best to stay with the Volvo part in the end as there is not much price difference (berth holders get a discount with Motortech) and that it would be easier for others if/when we sell her.

Here are some photos of the dismantled parts…
[attachment=2:3idkafh8]IMG_8209sm.jpg[/attachment:3idkafh8]
[attachment=1:3idkafh8]IMG_8212sm.jpg[/attachment:3idkafh8]
[attachment=0:3idkafh8]IMG_8218sm.jpg[/attachment:3idkafh8]

[Anonymous]

Do you have the Volvo part No?

[Anonymous]

Part number I have from Motortech which appears to be the Volvo part is 828064. List price is £205+VAT (berth holders ~185+VAT).

It is supposed to be corrosive resistant stainless, but they probably stated that for the original! Ours appears to have lasted 8 years but engine only has around 350 hours. I guess draining and washing it out at the end of each season might extend the life a bit!

[Author]

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