Wet Exhaust Setup Help Plz

[DrGonzoMIA]

Hi all, hope everyone is well.

 

I bought a big ol' 40ft Steel Motor cruiser last year to live on. Built in 1979 as far as I'm aware and moved from the sea to canals. It has a ginormous Leyland 6/98 5.7l diesel engine.

 

Haven't really been anywhere in it yet but want to make a start getting it a bit more refined. I appear to have a leak on the Vetus waterlock so got to googling exhaust systems and I'm not sure if my current setup is very good.  Please see rough sketch I have attached which is not far off what it looks like currently. Biggest concern is water backing into the engine once off. I've had an idea of getting a 76mm stainless steel exhaust section from a car to create a goose neck after the waterlock. Would that be a good idea ?! Vetus sell a goose neck but it's a ridiculous price and out of stock everywhere.

 

Many thanks for any help or wisdom you can throw my way.

 

[Tony Brooks]

One would normally expect a swan neck running up to well above the waterline close to the hull outlet with a vacuum beak valve or pipe at the top. Say at least 10" above the water line or more. Often this will be steel.

 

It seems modern practice is to fit a tall water separator very close to the hull outlet with the exhaust entering it high up.

 

More info here but be aware Vetus really charge for yellow paint. https://www.abcpm.co.uk/vetus/exhausts/

[GRLMK38]

Worth a taking a look at Maritime & Coastguard Agency document MGN629 - Part 3 Section 3.10. 

[Alan de Enfield]

48 minutes ago, GRLMK38 said:

Worth a taking a look at Maritime & Coastguard Agency document MGN629 - Part 3 Section 3.10. 

 

Good link.
I was always told that the water-lock  must be a minimum of 15" above the water line and the water lock 10" above below the manifild- if the OPs sketch is correct he stands a very good chance of filling the engine with water. Hopefully he has sketched it incorrectly.

 

The link shows 350mm so the same 15"

 

 

 

 

Edited January 13, 2022 by Alan de Enfield

[DrGonzoMIA]

Thankyou. This was what I planned to do. System already has a small anti syphon loop just after the heat exchanger. I wanted to add a 76mm stainless goose neck after the water lock. Would that need to be vented ??

 

I've looked at many a diagram on the Internet. Mainly Vetus. But also find conflicting information from so called experts....

 

Cheers

[DrGonzoMIA]

4 minutes ago, Alan de Enfield said:

 

Good link.
I was always told that the water-lock  must be a minimum of 15" above the water line and the water lock 10" above below the manifild- if the OPs sketch is correct he stands a very good chance of filling the engine with water. Hopefully he has sketched it incorrectly.

 

The link shows 350mm so the same 15"

 

 

 

 

That looks similar to what I propose. If the water lock was above the waterline it's not doing its job? It's intended to let water run down into it when engine off

[Alan de Enfield]

6 minutes ago, DrGonzoMIA said:

But also find conflicting information from so called experts...

 

How do you know if 'Mr Anonymous on the internet is really an "Expert" ?

 

If you go by the Govenments requirements (as posted by GRMLK38) then should the worse happen you can always tell your insurers it was installed to 'best practice', If you invent / modify a system to your own design then it would lead to "questions".

 

 

Edited January 13, 2022 by Alan de Enfield

[DrGonzoMIA]

True

 

[Steve56]

4 minutes ago, DrGonzoMIA said:

Thankyou. This was what I planned to do. System already has a small anti syphon loop just after the heat exchanger. I wanted to add a 76mm stainless goose neck after the water lock. Would that need to be vented ??

 

I've looked at many a diagram on the Internet. Mainly Vetus. But also find conflicting information from so called experts....

 

Cheers

The Swan neck does not need to be vented. The only weak spot I can see is your exhaust outlet is below water line. This is not uncommon but if you spring a leak in what looks to be a flexible pipe that will be a boat sinker. If it were me I would prefer solid pipework below water line. If the installation allows it may be worth looking at moving the exhaust outlet to a position above water line.

5 minutes ago, DrGonzoMIA said:

That looks similar to what I propose. If the water lock was above the waterline it's not doing its job? It's intended to let water run down into it when engine off

That is correct. All pipework must run downhill to the water lock. The 15 inch is probably talking about the water injection bend. This needs to be at about 15 inch above the water line or else you should fit an anti syphon valve. As the drawing shows you have one fitted so no problems.

[DrGonzoMIA]

Cool thankyou. Feel like I'm getting somewhere. The exhaust being below the waterline has always concerned me to be honest. I had to change a perished pipe a while back as it was leaking on the exhaust outlet. I had to ratchet strap the boat to the bank to lift the exhaust above the waterline to change the hose. I was hoping to find a one way valve but no. I do need to sort this somehow when it's out of the water next 

[Alan de Enfield]

Just now, DrGonzoMIA said:

Cool thankyou. Feel like I'm getting somewhere. The exhaust being below the waterline has always concerned me to be honest. I had to change a perished pipe a while back as it was leaking on the exhaust outlet. I had to ratchet strap the boat to the bank to lift the exhaust above the waterline to change the hose. I was hoping to find a one way valve but no. I do need to sort this somehow when it's out of the water next 

 

Dont worry - I have twin 6.2 litre "straight 6 engines" and both exhausts exit below the water line, it would be horendously nosiy if they exited above the water line (its bad enough as it is)

 

The lower hull fitting is the exhaust, the middle one is the 'tell-tale' and I cannot remember what the top one is.

I have 13 thru hull fittings on, or, below the water line.

 

 

[DrGonzoMIA]

If I do add the stainless goose neck will the exhaust be powerful enough to blast water around it without any other modifications? I'll try use slower bends for least resistance. I wouldn't imaging any backfilling water into the water lock would be an issue as currently its the canal that's back falling into it ?!

[DrGonzoMIA]

1 minute ago, Alan de Enfield said:

 

Dont worry - I have twin 6.2 litre "straight 6 engines" and both exhausts exit below the water line, it would be horendously nosiy if they exited above the water line (its bad enough as it is)

 

The lower hull fitting is the exhaust, the middle one is the 'tell-tale' and I cannot remember what the top one is.

I have 13 thru hull fittings on, or, below the water line.

 

 

Thankyou for that. My exhaust outlet is just below the waterline on port side. I can as mentioned tie it to bank to lift above waterline in case of emergency. Maybe I just need to fit a one way valve when it's out the water and not worry about it too much ?

[Alan de Enfield]

5 minutes ago, DrGonzoMIA said:

Thankyou for that. My exhaust outlet is just below the waterline on port side. I can as mentioned tie it to bank to lift above waterline in case of emergency. Maybe I just need to fit a one way valve when it's out the water and not worry about it too much ?

 

 

I have 2 toilets, each with a water in / black water out fitting (4 hull fittings)

2x Engines each with 'water' in, tell tail, and exhaust (6 hull fittings)

Pump-Out tank 'dump' Grey water & Black water (1 hull fitting)

Speed log (1 hull fitting)

Depth sounder (1 hull fitting)

 

On any non-exhaust thru hull fitting make sure you have GOOD sea-cock fittings and an assortment of wooded taper-plugs kept by each sea-cock.

The brass can 'de-zincify' leaving the brass very brittle and a slight knock can break the sea-cock so you then use the taper wooded plugs to stem the in-rush.

 

If your boat has come from the sea to fresh water you MUST change your anodes from Zinc to Magnesium, Zinc anodes provides very little protection to the steel when in fresh water.

[DrGonzoMIA]

Ok thankyou for advice. It's been in canal for some time I think but will deffo check.