I have a Next Generation (NextGen) 3.5 KW generator on BlueJacket. It has
an exhaust mixing elbow that combines the raw cooling water with the
exhaust and that flows into the muffler. You can see a picture of it at
http://www.geoffschultz.org/Ebay/Exhaust_Elbow.jpg

In theory this works well, but in practice, there are some severe problems.
The elbow develops internal leaks and raw cooling water can drip back into
the engine. I've been through 3 elbows and had to rebuild the engine once
due to a leak. I met other boats who have the same problems.

My plan is to replace the existing mixing elbow with a dry stack.
Basically I'll cut off the big round can and replace it with a 10" high
stainless tube U that will have the raw water entering 1/2 down the side
that connects to the muffler. I'll wrap the whole thing in insulation to
reduce the burn potential and heat.

Does this sound like a reasonable solution to this problem?

-- Geoff

On Fri, 20 Jul 2007 15:59:50 -0500, Geoff Schultz
wrote:

I have a Next Generation (NextGen) 3.5 KW generator on BlueJacket. It has
an exhaust mixing elbow that combines the raw cooling water with the
exhaust and that flows into the muffler. You can see a picture of it at
http://www.geoffschultz.org/Ebay/Exhaust_Elbow.jpg

In theory this works well, but in practice, there are some severe problems.
The elbow develops internal leaks and raw cooling water can drip back into
the engine. I've been through 3 elbows and had to rebuild the engine once
due to a leak. I met other boats who have the same problems.

My plan is to replace the existing mixing elbow with a dry stack.
Basically I'll cut off the big round can and replace it with a 10" high
stainless tube U that will have the raw water entering 1/2 down the side
that connects to the muffler. I'll wrap the whole thing in insulation to
reduce the burn potential and heat.

Does this sound like a reasonable solution to this problem?

-- Geoff

You can do that and it will work fine. The portion of the manifold
before the water is injected will be HOT so be sure there is some
clearance around it even though it is wrapped.

The way I build mine is to build the "U" and then mount the raw water
inlet near the top of the manifold but with the inlet pipe angled
downward toward the outlet end of the manifold. I also weld in a
threaded nipple at the low point of the manifold and mount a gate
valve there. When I shut down the engine I open the valve which (1)
drains any residual water and (2) keeps any water that subsequently
enters the exhaust out of the engine. It is probably over kill but on
the other hand I haven't gotten any water in the engine...


Bruce in Bangkok
(brucepaigeatgmaildotcom)

--
Posted via a free Usenet account from http://www.teranews.com

On Fri, 20 Jul 2007 15:59:50 -0500, Geoff Schultz
wrote:

My plan is to replace the existing mixing elbow with a dry stack.
Basically I'll cut off the big round can and replace it with a 10" high
stainless tube U that will have the raw water entering 1/2 down the side
that connects to the muffler. I'll wrap the whole thing in insulation to
reduce the burn potential and heat.

Does this sound like a reasonable solution to this problem?

Perhaps, but take note of Bruce's comments.

What you describe is not truly a dry stack but more closely resembles
a "riser" in power boat language. A true dry stack has no water entry
at all and usually exits vertically through the deck like a lobster
boat. Many commercial fisherman and some long range trawlers use dry
stacks and keel coolers to totally eliminate raw water cooling and
exhaust issues.

Wayne.B wrote in
:

On Fri, 20 Jul 2007 15:59:50 -0500, Geoff Schultz
wrote:

My plan is to replace the existing mixing elbow with a dry stack.
Basically I'll cut off the big round can and replace it with a 10"
high stainless tube U that will have the raw water entering 1/2 down
the side that connects to the muffler. I'll wrap the whole thing in
insulation to reduce the burn potential and heat.

Does this sound like a reasonable solution to this problem?

Perhaps, but take note of Bruce's comments.

What you describe is not truly a dry stack but more closely resembles
a "riser" in power boat language. A true dry stack has no water entry
at all and usually exits vertically through the deck like a lobster
boat. Many commercial fisherman and some long range trawlers use dry
stacks and keel coolers to totally eliminate raw water cooling and
exhaust issues.

Thanks for the nomenclature edification. I'm certainly not versed in this.
Regardless of what you call it, is this a reasonable solution? Based upon
the previous response, it sounds OK.

-- Geoff

On Sun, 22 Jul 2007 15:06:13 -0400, Wayne.B
wrote:

On Fri, 20 Jul 2007 15:59:50 -0500, Geoff Schultz
wrote:

My plan is to replace the existing mixing elbow with a dry stack.
Basically I'll cut off the big round can and replace it with a 10" high
stainless tube U that will have the raw water entering 1/2 down the side
that connects to the muffler. I'll wrap the whole thing in insulation to
reduce the burn potential and heat.

Does this sound like a reasonable solution to this problem?

Perhaps, but take note of Bruce's comments.

What you describe is not truly a dry stack but more closely resembles
a "riser" in power boat language. A true dry stack has no water entry
at all and usually exits vertically through the deck like a lobster
boat. Many commercial fisherman and some long range trawlers use dry
stacks and keel coolers to totally eliminate raw water cooling and
exhaust issues.

An added comment. According to some of the blokes standing around on
the jetty you are not supposed to use stainless to make exhaust parts.
NOT NEVER!

I have built boat exhaust systems out of both "black iron" and
stainless and can't really see much difference. Do use stainless pipe,
not tubing, as the pipe is much thicker and will last longer. My
present stainless elbow, on a 40 hp, engine, has passed ten years and
is still going strong.

Bruce in Bangkok
(brucepaigeatgmaildotcom)

--
Posted via a free Usenet account from http://www.teranews.com

"Bruce" wrote

An added comment. According to some of the blokes standing around on
the jetty you are not supposed to use stainless to make exhaust parts.
NOT NEVER!

If they know so much, why are they standing around on the jetty?

I've seen plenty of stainless exhaust componenents put in the million dollar
plus boats I design. Never heard of a problem. The "make exhaust parts"
part might be relevant because the parts I'm familiar with were bolted
together from pieces fabricated by people who make exhaust their business.

--
Roger Long

I replaced the elbow on my Lehman 135 about 4 years ago with a SS
version. Pulled it off earlier this year to inspect it and other than
a bit of black, it looks like new inside and out.

Bruce wrote in
:

On Sun, 22 Jul 2007 15:06:13 -0400, Wayne.B
wrote:

On Fri, 20 Jul 2007 15:59:50 -0500, Geoff Schultz
wrote:

My plan is to replace the existing mixing elbow with a dry stack.
Basically I'll cut off the big round can and replace it with a 10"
high stainless tube U that will have the raw water entering 1/2 down
the side that connects to the muffler. I'll wrap the whole thing in
insulation to reduce the burn potential and heat.

Does this sound like a reasonable solution to this problem?

Perhaps, but take note of Bruce's comments.

What you describe is not truly a dry stack but more closely resembles
a "riser" in power boat language. A true dry stack has no water entry
at all and usually exits vertically through the deck like a lobster
boat. Many commercial fisherman and some long range trawlers use dry
stacks and keel coolers to totally eliminate raw water cooling and
exhaust issues.

An added comment. According to some of the blokes standing around on
the jetty you are not supposed to use stainless to make exhaust parts.
NOT NEVER!

I have built boat exhaust systems out of both "black iron" and
stainless and can't really see much difference. Do use stainless pipe,
not tubing, as the pipe is much thicker and will last longer. My
present stainless elbow, on a 40 hp, engine, has passed ten years and
is still going strong.

Bruce in Bangkok
(brucepaigeatgmaildotcom)

I was planning on using schedule 40 SS pipe. Thanks for the feedback.

-- Geoff

On Sun, 22 Jul 2007 21:01:44 -0500, Geoff Schultz
wrote:

Thanks for the nomenclature edification. I'm certainly not versed in this.
Regardless of what you call it, is this a reasonable solution? Based upon
the previous response, it sounds OK.

Yes, it sounds reasonable with all of the usual caveats about proper
design, construction and installation.

One of the problems with many sailboat engines is that they are
frequently below the waterline which makes cooling water exit very
problematic. There is something called a water lift muffler which is
supposed to alleviate this issue by creating a "one way" valve in the
exhaust flow. My old Cal-34 had one but it eventually malfunctioned
and allowed water ingress in a following sea. Fortunately the Atomic
4 had nine lives and always recovered from such mistreatment but it
was a nuisance at best. Eventually I installed a rubber flapper valve
at the transom exit and that solved the problem.

Wayne.B wrote in
:

On Sun, 22 Jul 2007 21:01:44 -0500, Geoff Schultz
wrote:

Thanks for the nomenclature edification. I'm certainly not versed in
this. Regardless of what you call it, is this a reasonable solution?
Based upon the previous response, it sounds OK.

Yes, it sounds reasonable with all of the usual caveats about proper
design, construction and installation.

One of the problems with many sailboat engines is that they are
frequently below the waterline which makes cooling water exit very
problematic. There is something called a water lift muffler which is
supposed to alleviate this issue by creating a "one way" valve in the
exhaust flow. My old Cal-34 had one but it eventually malfunctioned
and allowed water ingress in a following sea. Fortunately the Atomic
4 had nine lives and always recovered from such mistreatment but it
was a nuisance at best. Eventually I installed a rubber flapper valve
at the transom exit and that solved the problem.

All that I'm doing is replacing the mixing elbow with this riser and all of
the other components are remaining the same. The output of the riser will
go to the water lift muffler. I haven't had issues ingress issues.

-- Geoff