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Christopher Bruce
Mar 28, 2012 - 9:07PM
Blocked exhaust - I think!
Hi
I have a problem which I think is a blocked exhaust. I can't get above 1000 rpm and there is an exhaust leak under what I think is called the exhaust trap. It's what looks like a cast iron unit, under the port side cockpit hatch, which the exhaust enters and then exits under aft cabin to the stern. I think that this unit is blocked. If I'm correct can I unblock this unit? It's going to be a horrible to take off.
Can anyone give me advice.
Regards
Chris
SeaDog Name (if owner or crew) Natuna
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Graham
Mar 29, 2012 - 7:17AM
Re: Blocked exhaust - I think!
Sounds likely to be the cause yes. The cast iron box is often referred to as a Parsons Box. It can be stripped and revived using plumbing parts but many SeaDog owners have chosen to replace it either with a stainless steel copy or by using vetus plastic components.
Before removing it though you may want to check the rubber exhaust hose and seacock that lead to the transom. The rubber hose has been known to de-laminate and collapse, causing a blockage. The pressure would then probably show itself as leak through the weakest point, the jubilee clip on the parsons box.
Graham
SeaDog Name (if owner or crew) Dougal
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Eric Richardson
Mar 29, 2012 - 8:45AM
Re: Blocked exhaust - I think!
Hi Chris
I think Graham has given you the most likely answer to your question. What happens is that when the rubber exhaust delaminates pressure gets between the layers and clamps the inner section down. You have the usual syptoms of running OK at tickover, then as you increase exhaust guantity it reduces its flow capacity and strangles the engine.
The gas pressure can cause water to feed back to the engine when you shut down so sort it now.
I prefer the Vetus full wet exhaust system and it is easy to fit on the Seadog.
Eric
Chris Bruce
Mar 29, 2012 - 11:02AM
Re: Blocked exhaust - I think!
Thanks Eric. Will look at the rubber hose it I have a feeling this is the problem. Any ideas where I could get a replacement.
Chris
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Chris Bruce
Mar 29, 2012 - 11:04AM
Re: Blocked exhaust - I think!
Thanks Graham. Will look at the rubber hose. I have a feeling this is the problem. Any ideas where I could get a replacement.
Chris
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Graham
Mar 29, 2012 - 11:18AM
Re: Blocked exhaust - I think!
Eric may know of a cheaper option but if not then any good chandlers should have some or at least be able to order it for you. If Natuna is afloat you will need to carefully check the the outlet seacock is functioning before replacement as the exit at the transom can easily dip below the water line (especially if loaded as Dougal usually is:-))
Access is not to bad stripping the bunks in the aft cabin, most difficult part is the bottom of the parsons box. Not sure of the size, you will need to measure.
Good luck, let us know how you get on.
Graham
SeaDog Name (if owner or crew) Dougal
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Chris Bruce
Mar 29, 2012 - 11:30AM
Re: Blocked exhaust - I think!
Thanks Graham I'm just off to the Marina to do an investigation. I agree that the connetion to the Parsons box will be a challenge to disconnect.
Thanks also for the warning about the outlet seacock. I will make sure it's functioning before replacement altough I the exit at the transom is above sea level.
I want to crack this problem today as I'm off to UK tomorrow in the car and there are many more Chandlers in UK than Ireland.
Chris
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Eric Richardson
Mar 30, 2012 - 9:49AM
Re: Blocked exhaust - I think!
Hi Chris
A company called ASAP Supplies at Beccles in Norfolk do all that type of gear. They have an online catalogue and I have found them OK.
Phone number 08451300870.
As Graham says make sure the outlet is above water or plug it tight.
Eric
Christopher Bruce
Mar 30, 2012 - 10:43AM
Re: Blocked exhaust - I think!
Hi Eric
Thanks for that. Have located it at Force 4 in Bristol and will collect when I'm there on Tuesday. Spent time yesterday bending over double in the aft cabin. As is usual with these jobs I now have aches in places I didn't know I had!!
Thanks for all the help will keep you informed.
Chris
SeaDog Name (if owner or crew) Natuna
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Christopher Bruce
Apr 9, 2012 - 10:05PM
Re: Blocked exhaust - I think!
Hi Eric
Tool out Parsons box today and the exhaust was completely blocked not sure how the engine was exhausting. The parsons box is in a bad way so I think I will have to replace it. You mentioned the option of replacing it with a Vetus box, could you advise me on this. Also I had to cut the stainless steel exhaust pipe at the manifold end so I'm going have to replace this. Any ideas where I can source this. Sorry to ask you so many questions.
Regards
Chris
SeaDog Name (if owner or crew) Natuna
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Graham
Apr 10, 2012 - 7:20AM
Re: Blocked exhaust - I think!
Hi,
I am sure Eric will be along soon with the expert technical stuff but in the meantime you may want to take a look at the Vetus catalogue. The printed one is best but a digital version is online at http://viewer.zmags.com/publication/06f … 06fa8bec/1
Exhaust systems start on page 64. You will need a water lock a gooseneck and an anti-siphon valve, I wouldn't bother with a muffler, not needed and no room anyway. I used the round waterlock set near the engine (handy because the inlets and outlets rotate to align with the exhaust. The other components are mounted in the space where the parsons box used to be.
SeaDog Name (if owner or crew) Dougal
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Graham
Apr 10, 2012 - 7:28AM
Re: Blocked exhaust - I think!
Just discovered that there are individual 'installation manuals' available on the Vetus website too. They can be downloaded onto your computer and printed if required. The list for exhaust components starts at http://www.vetusweb.com/manuals_42.php
Just click on each component that you want to read about.
Graham
SeaDog Name (if owner or crew) Dougal
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Chris Bruce
Apr 12, 2012 - 5:45PM
Re: Blocked exhaust - I think!
Hi Graham et all
Took out the Parsons Box, tried to split it and of course after 40 years+ it cracked. So that's that. I can't use the plastic Vetus solution as I have a dry exhaust and the plastic would melt. Obviously I can't get a replacement Parsons box so I'm down to a Stainless Steel clone. Do you know anyone who has used a stainless steel box and if so where they got it from. I have spoken to one person in Essex who could fabricate me one but I'm looking at about £600. The Vetus box is £189.00!! Any help you or anyone could give me would really be appreciated.
Regards
Chris
SeaDog Name (if owner or crew) Natuna
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Graham
Apr 12, 2012 - 9:49PM
Re: Blocked exhaust - I think!
Hi Chris,
The stainless replacements I have seen have been custom made, Steve Woodland (Glory) made one of them but I think it went onto another SeaDog after he changed to a wet exhaust. The cheaper and better option is to convert to a wet exhaust.
The vetus system we have was installed at the same time as our replacement BetaMarine engine but I know that they can also be fitted to the Perkins.
What you need to do is get someone to fabricate a water injection elbow that would attach to the exhaust manifold. Ours was deigned and made by Scotty at TS marine on the Hamble. I can't remember all the details but the principle is that you have a metal loop that takes the exhaust as high as practical then turns down where another metal tube is grafted on to connect the water injection.
BetaMarine do two versions and I chose the 'high rise' version but scotty still modified it to take it higher (must go above the waterline). The standard high rise can be seen on this page http://www.betamarinenc.com/images/small_8.jpg
hope all this helps.
Graham
SeaDog Name (if owner or crew) Dougal
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Eric Richardson
Apr 17, 2012 - 8:20PM
Re: Blocked exhaust - I think!
Hi Chris
Sorry for not getting back to you, I have had a week working on the boat at Lowestoft. The main advantage of the Wet exhaust system is the it starts with a water injection bend at the exhaust manifold and is wet and therefore cooled for its entire length. This does away with that length of flexible steel pipe that gives trouble by loosing its flexibility. See the Vetus webb site as Graham says its all very easy to sort out and quite reliable.
Eric
Lesley verbrugge
Feb 24, 2014 - 9:16AM
Re: Blocked exhaust - I think!
This comment is a bit late, found the posting when researching something completely different and going off on a tangent.
We have one aboard our Rival 41 and the previous owner gave me the contact details for replacement. he also stressed that although unknown to many, this was the best set up for our boat. we also have a vetus plastic trap in the exhaust hose after this
Thought I'd post for anyone trying to find a replacement in the future.
Golden arrow marine Ltd
Www.golden arrow.co.uk they were (2011) at Shamrock Quay which is near Portsmouth (?) UK
I will post the pictures I have of what the parson's box or 'parson's injector' looks like when dismantled, on our website www.huntingjunks.org look in posts category boatwork. If they aren't there when you look, remind me by emailing using the contact form on the website.
Regards
Lesley
Ps I was a member of this forum when we first started looking for boats back on 2007!
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Lesley Verbrugge
Apr 30, 2014 - 3:54PM
Re: Blocked exhaust - I think!
Update.
Golden marine no longer supply, but one of their staff contacted Mark Jenkins who used to own Parsons. he in turn gave me the contact details for a company that manufactures for him. Suggest anyone interested in this fascinating subject, contact me for further details! BTW for those unaware, there' s an excellent article on rebuilding a parsons box here on this site which might help someone in the future?
Lesley
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