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Webasto exhaust skin fitting diameter advice/guidance?


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I have found the perfect place for my refurbed Webasto Thermo Top C in my engine bay - close to the fuel line, batteries, etc. For the exhaust outlet, I am thinking about using an existing skin fitting from the bilge pump. It is high up, in a perfect location, and a welded in one (steel). However, I wanted to ask if anyone knows if there was a minimum diameter an exhaust skin fitting needed to be for a Webasto boiler? (I mean the hole that the fumes escape through, not the entire skin fitting diameter.)

 

This hole diameter of the existing one is 13/14mm. And my Webasto exhaust pipe fits nice and snuggly over it otherwise :)

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The internal diameter of the exhaust tube is typically 25mm. A 13mm internal diameter skin fitting would restrict the exhaust gas to a quarter of the area to flow through. The more usual exhaust skin fittings have very thin walls in stainless steel. Only a millimetre or less, so much less restrictive.

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Make up a long conical piece pf wood and drill the center to about 6mm. Bang into existing hole from the outside, cut off flush with the hull and use the hole in the wood as a pilot for a hole saw of the correct size, but cut slowly with plenty of lube./cooling. Be ready for it to take an hour or so. Then fit the approved skin fitting.

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When you say 'refurbed' is it one of the cheapy ebay ones ?

 

Assuming it is the proper Marine Webasto (and not the automotive version) then it would be supplied with the correct skin fitting as part of the exhaust kit.

That would give you the correct size and allow the exhaust pipe to be fitted using the proper components.

 

The correct marine exhaust fitting is 24mm.

 

If yours is only 13 / 14mm have you got the automotive exhaust ?

 

The automotive exhaust should not be used in a boat becasue it has condensate holes in it and it allows the exhaust gasses (including Carbon Monoxide) to build up in the boat bilges until one day you 'wake up dead'.

 

 

Marine skin fitting :

 

Picture 1 of 1

 

 

Is the silencer a 'square' or a long cylinder ?

 

The 'square' one is an automotive one, whilst the 'cylinder' is the correct boat silencer / exhaust.

 

 

Boat silencer / exhaust pipe

 

 

Eberspacher & Webasto MARINE EXHAUST SILENCER 30MM 2M LONG - Picture 1 of 1

Edited by Alan de Enfield
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3 hours ago, Alan de Enfield said:

When you say 'refurbed' is it one of the cheapy ebay ones ?

 

Assuming it is the proper Marine Webasto (and not the automotive version) then it would be supplied with the correct skin fitting as part of the exhaust kit.

That would give you the correct size and allow the exhaust pipe to be fitted using the proper components.

 

The correct marine exhaust fitting is 24mm.

 

If yours is only 13 / 14mm have you got the automotive exhaust ?

 

The automotive exhaust should not be used in a boat becasue it has condensate holes in it and it allows the exhaust gasses (including Carbon Monoxide) to build up in the boat bilges until one day you 'wake up dead'.

 

 

Marine skin fitting :

 

Picture 1 of 1

 

 

Is the silencer a 'square' or a long cylinder ?

 

The 'square' one is an automotive one, whilst the 'cylinder' is the correct boat silencer / exhaust.

 

 

Boat silencer / exhaust pipe

 

 

Eberspacher & Webasto MARINE EXHAUST SILENCER 30MM 2M LONG - Picture 1 of 1

 

 

I'd be inclined to recommend the version with lagging fitted.

 

image.png.4fa4479fc3e16720cac336cdb448ea06.png

 

https://www.melloronline.co.uk/Heater_Installation_Accessories_/10122/Marine_Exhaust_Silencer_with_lagging_24mm_2m_lg.html

 

 

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12 hours ago, Tony Brooks said:

Make up a long conical piece pf wood and drill the center to about 6mm. Bang into existing hole from the outside, cut off flush with the hull and use the hole in the wood as a pilot for a hole saw of the correct size, but cut slowly with plenty of lube./cooling. Be ready for it to take an hour or so. Then fit the approved skin fitting.

 

Thanks Tony, this is a great suggestion on how to tackle this problem! :)

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Thanks @Alan de Enfield - The unit itself is refurbed, but I have sourced the other kit parts from Webasto, Mellor, other online places, etc. 

 

I hadn't bought an exhaust skin fitting yet, as my query was whether I could use an existing welded on skin fitting that was previously used for the bilge pump's outlet. It seems that, no, it would not be wide enough, so I will go ahead and buy a marine skin fitting as you suggested, and take @Tony Brooks's advice on how to drill the new hole :) 

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26 minutes ago, aaronwood66 said:

Thanks @Alan de Enfield - The unit itself is refurbed, but I have sourced the other kit parts from Webasto, Mellor, other online places, etc. 

 

I hadn't bought an exhaust skin fitting yet, as my query was whether I could use an existing welded on skin fitting that was previously used for the bilge pump's outlet. It seems that, no, it would not be wide enough, so I will go ahead and buy a marine skin fitting as you suggested, and take @Tony Brooks's advice on how to drill the new hole :) 

 

I think that is the best way.

 

If your exhaust pipe fits thru a 13mm hull fitting do you have the correct exhaust pipe and silencer ?

 

If it is not a marine version then the electronics need reprogramming for use at different voltages. A vehicle start battery is always at virtually full charge (12.7v) and will 'kick' a heater into action, whilst a boat domestic battery bank can be quite discharged to (maybe) 12v - 12.2 volts and will struggle to start a non-marine version of heater.

 

You have not yet said if it is a refurbed Automotive one from ebay - but - if it is you may find that you need to start your engine and get the alternator putting out some 'charge' to be able to get the heater to run. Once running it will be OK on the lower voltages, unless it is on a thermostat and switches off and tries to start again.

Edited by Alan de Enfield
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6 minutes ago, Martin Nicholas said:

Concentric hole saws - two on the same mandrel - will make the opening bigger for you. Use cutting oil (WD40 is not cutting oil).

 

Not sure what type of hole saw you are talking about. There is no way the common hole saws that allow concentric mounting of blades will cut through a 6mm hull plate. The ones I know about that will can not accept a second saw on the common mandrel. If they did it would be ideal.

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8 hours ago, ditchcrawler said:

Good cutting oil makes the world of difference even if just drilling holes

 

Thanks for the tip - I will do anything that makes this easier!

8 hours ago, Alan de Enfield said:

If your exhaust pipe fits thru a 13mm hull fitting do you have the correct exhaust pipe and silencer ?

 

You have not yet said if it is a refurbed Automotive one from ebay - but - if it is you may find that you need to start your engine and get the alternator putting out some 'charge' to be able to get the heater to run. Once running it will be OK on the lower voltages, unless it is on a thermostat and switches off and tries to start again.

 

@Alan de Enfield Sorry, I didn't mean the exhaust pipe fits through a 13mm hole, but that is the opening diameter of this skin fitting I have. This welded on skin fitting has rather thick walls, so the marine exhaust hose/pipe fits nicely snuggly over it. Anyway, I will be removing this completely now :)

It is a refurbed marine one from ebay.

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20 hours ago, Tony Brooks said:

 

Not sure what type of hole saw you are talking about. There is no way the common hole saws that allow concentric mounting of blades will cut through a 6mm hull plate. The ones I know about that will can not accept a second saw on the common mandrel. If they did it would be ideal.

My pretty bog standard Screwfix set will take stacked saws. I use a spacer (a nut) too, so the inner one pokes out a few mm.

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1 hour ago, Martin Nicholas said:

My pretty bog standard Screwfix set will take stacked saws. I use a spacer (a nut) too, so the inner one pokes out a few mm.

 

Mine came from Screwfix a few years ago and neither the small mandrel nor the larger one has  along enough thread, let alone a thread long enough to put a nut between the two. In fact the larger one uses a sliding disk with two pins in it to stop the saw tightening itself onto the mandrel and those two pins are only long enough to locate in the top of a single saw. If the OP

1 hour ago, Martin Nicholas said:

My pretty bog standard Screwfix set will take stacked saws. I use a spacer (a nut) too, so the inner one pokes out a few mm.

 

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2 hours ago, Tony Brooks said:

 . In fact the larger one uses a sliding disk with two pins in it to stop the saw tightening itself onto the mandrel and those two pins are only long enough to locate in the top of a single saw. If the OP

 

Same as mine

 

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On 03/12/2022 at 21:24, Alan de Enfield said:

 

 

Marine skin fitting :

 

Picture 1 of 1

 

 

I did have one follow up question, now that I am going to go with a new marine exhaust skin fitting... I know the importance of creating a swan neck with the exhaust pipe, so wondered which way up I should install this skin fitting? I imagined with the angle pointing upwards, so as to create the upward angle for the swan neck - but a lot of videos/images show it pointing downwards

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1 hour ago, aaronwood66 said:

 

I did have one follow up question, now that I am going to go with a new marine exhaust skin fitting... I know the importance of creating a swan neck with the exhaust pipe, so wondered which way up I should install this skin fitting? I imagined with the angle pointing upwards, so as to create the upward angle for the swan neck - but a lot of videos/images show it pointing downwards

 

You wouldn't want the 'Webasto' on the outer flange upside down would you ?

 

But as the cyclist says - 'spout' upwards.

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1 hour ago, aaronwood66 said:

 

I did have one follow up question, now that I am going to go with a new marine exhaust skin fitting... I know the importance of creating a swan neck with the exhaust pipe, so wondered which way up I should install this skin fitting? I imagined with the angle pointing upwards, so as to create the upward angle for the swan neck - but a lot of videos/images show it pointing downwards

I have experienced the heater refusing to run one wet,cold night.

The cause (which I found eventually) was water in the exhaust pipe.

The LED screen showed error code E10, which was not very helpful, as the handbook only showed error codes up to E8!

Water got into the exhaust descending a lock with water squirting out of the stonework and a squirt obviously lined up with the exhaust outlet.

The exhaust pipe did not have a swan neck.

Turned the hull fitting to point upwards and now has a swan neck.

 

Experience is the best teacher, but sometimes the tuition fees can be a bit high!  😰

 

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2 minutes ago, Mad Harold said:

I have experienced the heater refusing to run one wet,cold night.

The cause (which I found eventually) was water in the exhaust pipe.

The LED screen showed error code E10, which was not very helpful, as the handbook only showed error codes up to E8!

Water got into the exhaust descending a lock with water squirting out of the stonework and a squirt obviously lined up with the exhaust outlet.

The exhaust pipe did not have a swan neck.

Turned the hull fitting to point upwards and now has a swan neck.

 

Experience is the best teacher, but sometimes the tuition fees can be a bit high!  😰

 

 

 

And just to think if C&RT were 'on top' of their maintenance you'd never have found out it was incorrectly installed.

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