exhaust hose system

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dleroc

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I have a Yanmar 1GM in my Halcyon 23 and I have leaks in the exhaust pipe system. A flexible hose (51mm) is fitted to the elbow and secured with a jubilee clip. This hose then connects to a 41mm stainless steel tube which is about 18" long. It looks like a piece of reinforced tubing has been fitted at both ends of the ss tube to provide a seal. Fumes and exhaust water escape from both these joints.

Apart from finding something to take the place of the reinforced tubing, is it normal to have an exhaust system with so many vulnerable joints?
 
I don't quite understand your description, but it sounds like a bodge. A normal exhaust system would go from the engine to a water trap, then to the hull fitting, possibly via a swan neck (if a manufactured swan neck fitting isn't used then the hose should be routed so that it performs the same function). All the fittings should have the same diameter to fit the hose, which should be securely jubilee clipped at each joint (double clips often advocated) and definitely not leaking.

Pete
 
I think you have mismatched diameters between fittings e.g. the ID of the hose is too big for the OD of the stainless steel tubing and a bodge has been used to make a seal. A solid reducer piece should be made or purchased to connect different hose IDs.

Examples of GRP parts specifically designed for connecting exhaust hoses of different diameters, should this be your problem : - http://halyard.eu.com/pleasurecraft/productdetails?product=32&category=Exhaust Systems

Halyard make a full range of GRP bends and adaptors. All are fabricated from our special high temperature GRP tube and designed to get you round 45°, 90° and 180° bends, or to couple hoses of differing diameters.
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BlowingOldBoots said:
I think you have mismatched diameters between fittings e.g. the ID of the hose is too big for the OD of the stainless steel tubing and a bodge has been used to make a seal. A solid reducer piece should be made or purchased to connect different hose IDs.
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If the stainless tube is just a length of tube, then I think it itself is part of the bodge. No point making adaptors to it, just get rid of it. Ideally replace the whole run of hose from engine to whatever is at the other end (next fitting beyond the tube), or failing that use short lengths of 51mm tube as couplers.

Pete
 
Thanks for your constructive replies. Yes, it certainly looks like a bodge which has basically survived one season since I bought the boat. There is no water trap but the rear hose is bent in a swan neck shape so i guess that's ok.
Ideally I would like to replace the whole length but that will have to wait until when i get it out of the water in a few months time.
In the meantime I think I will need to fit a reducer (as you suggest Pete) or something similar to last the next few months.
 
prv said:
If the stainless tube is just a length of tube, then I think it itself is part of the bodge. No point making adaptors to it, just get rid of it. Ideally replace the whole run of hose from engine to whatever is at the other end (next fitting beyond the tube), or failing that use short lengths of 51mm tube as couplers.

Pete
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Obviously there wouldn't be if the pipe was just a pipe to extend bits of odd hose. Not sure what point your making here as we only know what the OP has told us.
 
BlowingOldBoots said:
Not sure what point your making here
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Only that there is no point expending any effort or money in making adaptors, as you suggested, to something that shouldn't be there in the first place. Better to spend that effort and money (or with any luck, less) in replacing the whole lot with something more appropriate.

Pete
 
It's essential the exhaust system on a marine engine is absolutely bulletproof, don't mess about fit all new Vetus exhaust hose, water trap, gooseneck, and a muffler if you have the room. Double clip the joins if there's room.
 
savageseadog said:
It's essential the exhaust system on a marine engine is absolutely bulletproof, don't mess about fit all new Vetus exhaust hose, water trap, gooseneck, and a muffler if you have the room. Double clip the joins if there's room.
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+1, no need to go Vetus though, good quality Lloyds approved hose is available much cheaper. When you do it scrap the jubilee clips and fit proper Mikalor type of the correct size as Jubilee clips are not suited for hose that heavy. http://www.agriemach.com/p14754-mikalor-supra-304-stainless-steel-w4-clamps-59-63mm-25x-pack?gclid=CM66x8Gg-cYCFTDItAodQ3IOTw
 
It sounds like a bodge to bridge the gap when a water trap failed! I'd take a look at the Vetus catalogue as it has diagrams to demonstrate best practice to suit various installations depending on whether the engine's exhaust port is above or below the waterline. If the engine is below or near the waterline, its contents can be sucked back into the engine causing extensive damage. This is the principal function of the water trap, to break the flow back and catch the water in a safe container. It does have the extra bonus of acting as a silencer as the exhaust gas expands in the chamber and dissipates further energy as it bubbles through the sump full of water.

Even with the engine above the heeled waterline the water trap provides belt and braces safety plus the other benefits of silencing. Most installations also have a syphon break in the water feed from the engine to the exhaust elbow, although some are taken from other points in the flow taking it from the last run ensures maximum cooling throughout. The syphon break does just what it says on the tin and you can safely stop the engine without the seawater syphoming into the exhaust and overfilling the water trap. Two types of break are made, one simply has a flap valve so when there is no pressure in the line it opens to adnit air so no syphon. The other type has no valve, just a small line tapped off so a tell tale can be taken through a skin fitting or into a cockpit drain - if it.s squirting you know you have water flowing.

I guess this demonstrates that most wet exhausts have quite a few joints. It is best practice to double clip them all for added security, keep a regular eye on them and fit a carbon monoxide alarm in the cabin. If correctly routed and secured, to prevent vibration and chafe they really only need checking every few months - might as well add it to the other cursory checks you do on a rainy day.

Rob.
 
Thanks for all your replies so far. I don't think that there has ever been a water box fitted due to space constraints. The exhaust elbow is well above the water line.
Your prompt replies are appreciated and confirm the value of this forum.
 
++1 - dont use jubliee clips. Nowhere near strong enough. Just a thought - if a jubliee clip is all that holds the pipes onto the stainless section, replacing them with proper ones (which tighten down with a bolt through them) might just solve your problem for the rest of this season. Its almost impossible to get a decent seal on heavy exhaust hose with jubilee clips. If it doesnt work, then at least you have them for when you replace the whole pipe!
 
oldharry said:
++1 - dont use jubliee clips. Nowhere near strong enough. Just a thought - if a jubliee clip is all that holds the pipes onto the stainless section, replacing them with proper ones (which tighten down with a bolt through them) might just solve your problem for the rest of this season. Its almost impossible to get a decent seal on heavy exhaust hose with jubilee clips. If it doesnt work, then at least you have them for when you replace the whole pipe!
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The latest types of exhaust hose are much easier to run and to clamp than the old wire reinforced type where you had to remove the wire to get a good seal.
 
prv said:
If the stainless tube is just a length of tube, then I think it itself is part of the bodge. No point making adaptors to it, just get rid of it. Ideally replace the whole run of hose from engine to whatever is at the other end (next fitting beyond the tube), or failing that use short lengths of 51mm tube as couplers.

Pete
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+1

What size is your exhaust outlet through the hull? Do you have a silencer or anything else (apart from the stainless tubing) between the engine and that outlet? If so what diameter are they?
 
dleroc said:
Thanks for all your replies so far. I don't think that there has ever been a water box fitted due to space constraints. The exhaust elbow is well above the water line.
Your prompt replies are appreciated and confirm the value of this forum.
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Even with the elbow above the waterline you need a water trap. There are various types from Vetus or Halyard Marine. Not only do they collect the water that gets left in the system when you shut down but they significantly reduce the noise from the exhaust.
 
Tranona said:
Even with the elbow above the waterline you need a water trap. There are various types from Vetus or Halyard Marine. Not only do they collect the water that gets left in the system when you shut down but they significantly reduce the noise from the exhaust.
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+1.
The height of exhaust elbow relative to sea-level principally determines whether an anti-syphon loop is required, not whether a water-trap is necessary. Whether a water trap is essential depends most of all on the volume and disposition of the exhaust system. Vetus recommends that one assumes that 50% of the exhaust hose volume is water at shut-down (allowing for a comfortable safety margin). A silencer has some (very modest) water-trap properties. Vetus silencers are about 18" long (the size of the OP's gap). Being much more compact than a water trap, perhaps fitting one might solve the OP's problem,. Before considering that, however, he should do the calculations for exhaust volume. The Vetus website (and no doubt others) has the information required, including a friendly little calculator.
 
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IMO the correct bit of ss tube is a real assett in the exhaust system.
I beleave that the most common place for the hose to fail is in the first section from the exhaust elbow. To be able to replace just that bit makes life simple, easier, quicker and less expensive than having to replace the whole length.
I have put a ss elbow about a mtr away from the exhaust elbow where the hose turns from its downward path to horizontal.
 
LadyInBed said:
I beleave that the most common place for the hose to fail is in the first section from the exhaust elbow. To be able to replace just that bit makes life simple, easier, quicker and less expensive than having to replace the whole length.
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That'll be the bit that commonly links the exhaust elbow to the water-trap, thereby solving your problem by slightly different means.
 
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