Question About Copper Exhaust System.

[JOHNMARDALL]

I can't tell if this is a wet exhaust system or dry, so I'll respond to both.


1. There has to be a flexible coupling or hose between the exhaust system and the engine, because the engine moves on its flexible mounts.


2. If the exhaust system is wet, with raw water from the heat exchanger being injected into the exhaust gas right after the exhaust manifold, in a mixing elbow, the exhaust system temperature will not exceed 70 Celsius and there will be no melting problems with solder or brazing, However, the salt water and warm gas combination will eat through the solder or brazing, and eventually even the copper, usually causing multiple pin hole leaks before total failure with joints coming apart. Not good.
3. If this is a dry system, with no water injection, wrapping the components will increase their temperature and increase the probability of the joints failing. Exhaust gas temperatures range from 500 to 1000 Celsius. In addition, anything that this system touches will have to be insulated from it.




These are some of the reasons why boat builders do not use copper plumbing pipes and fittings to make exhaust system. In spite of the cost, you're better off installing a real marine exhaust system than risking your boat and your life with this amateur installation.


Let me know if you need more information or input on this.


Good luck


John Mardall
Vetus Group

[dgz3]

I'm with your mechanic on this one. That thing looks like a plumber went on an acid trip in your engine room. And whoever mentioned hose barbs has a good point.
If that contraption ever springs a leak or cracks, you'll pay the devil getting it fixed. I would much rather see a collection of commonly available threaded fittings and adaptors assembled to accomplish the same purpose.
If you start over with a fresh outlook, eliminating the need for custom fabrication, you may be able to simplify the whole system. Might cost you a bit now, but maybe save you a bunch later.

[Midnight Son]

Hot diesels produce mostly CO2, with some CO and NOx and a smidge of Fomaldehyde. Ditch the plumbers nightmare and do it right, you and your familys' health and safety is at stake.

[Rorzech]

By the looks of that purplish oxidation on the braze I would guess it was brazed with Silfos which is a silver phosphorus alloy which melts around 1,300 F. Plenty strong and corrosive resistant from the carbonic acid produced by the diesel exhaust. Copper is a great heat conductor . If you're worried about the non-jacketed copper , just wrap new 1/4 " soft refrigeration copper tightly around it and cover every bit of the pipe with it that new copper will bend like butter without kinking. Hook up the "heat trace tube" to your water flow and it'll stay cool. Diesel is not very hot compared to gas exhaust. There is all sorts of heat absorbing and repelling and insulating products on the market and lots of good Ideas on this forum. Let us know how you make out with it because Im putting a diesel in place of my Atomic 4 . Cheers.

[reed1v]

Just avoid stainless. way too brittle. Copper is way more forgiving.

[reed1v]

Originally Posted by JOHNMARDALL

I can't tell if this is a wet exhaust system or dry, so I'll respond to both.


1. There has to be a flexible coupling or hose between the exhaust system and the engine, because the engine moves on its flexible mounts.


2. If the exhaust system is wet, with raw water from the heat exchanger being injected into the exhaust gas right after the exhaust manifold, in a mixing elbow, the exhaust system temperature will not exceed 70 Celsius and there will be no melting problems with solder or brazing, However, the salt water and warm gas combination will eat through the solder or brazing, and eventually even the copper, usually causing multiple pin hole leaks before total failure with joints coming apart. Not good.
3. If this is a dry system, with no water injection, wrapping the components will increase their temperature and increase the probability of the joints failing. Exhaust gas temperatures range from 500 to 1000 Celsius. In addition, anything that this system touches will have to be insulated from it.




These are some of the reasons why boat builders do not use copper plumbing pipes and fittings to make exhaust system. In spite of the cost, you're better off installing a real marine exhaust system than risking your boat and your life with this amateur installation.


Let me know if you need more information or input on this.


Good luck


John Mardall
Vetus Group

Obviously you know your stuff. I will tell the rest of Maine boat builders what you say since copper is used a lot in the commercial engine rooms of boats up here. Might even need to recall some of the hundred plus year old yachts Hodgdon built to replace all that worn out copper. Thanks for your timely advice. Who would have thunk after two hundred years they were doing it wrong.

[topmast]

Doing things wrong due to a lack of skill or a lack of experience is just what we often see. Threads like this may help to clear things. If one already knows the answers it won't help a bit. But some may benefit.My experience is from years of trial /error and fixing others screwups. and coming from a material tech background I still measure stuff by does it work and the numbers are secondary.

[frozenhawaiian]

thank so much for all the input guys. I really appreciate it guys

[boatpoker]

Copper over-tempers with vibration and becomes brittle. this is the same reason one must not use solid core copper wiring in your electrical system.

[model 10]

Originally Posted by topmast

I still measure stuff by does it work and the numbers are secondary.

The numbers I see for copper are a max operating temp of 536 deg F in water. No mention of the mix of exhaust and water.
Another use for a thermometer gun. I finally bought one for myself. I'm looking forward to shooting up our boat.

[topmast]

Even warm salt water deflecting off a metal surface as it injects into a mixer can cut like butter in a short time. I usually angle the welded nipple so the water gets into the rubber hose before it actually hits the metal. This keeps the mixer metal cool enough through direct conduction. successful exhaust systems are cheap and proven and no need to reinvent .