# Air cooled engine with wet exhaust?



## nsweeting (Sep 30, 2011)

Hi there,

My girlfriend and I recently invested our lives and money into a sailboat. Our goal of cruising towards Cuba has unfortunately come to a bit of a standstill as some of the current realities with our boat have made themselves seen. 

We are now in Beaufort, SC - and time has come to make some tough decisions. I would hate to say stuck, as it is a wonderful town!

The boat is a beautifully crafted George Buehler steel cutter. Not just a home build either - done by professionals at a boat yard. We are still very happy with the purchase. Incredibly solid - built to face almost anything. BUT, there are some quirks that need to be worked out before we can move forward.

The main one being our exhaust system. We have a Deutz 303-1 air cooled engine. Everything I have read and researched about Deutz engines has been positive. It is a little bit underpowered for our boat weight - but nothing that cant be managed. All in all - the engine is in great condition, runs really well, and I'm happy with it. 

Unfortunately, the show stopper at the moment is the exhaust system that was coupled with the engine. A dry exhaust runs to the stern of the boat. Whoever installed the dry exhaust seemed to have known what they were doing - but it seems to be a poor match with this engine. It is a rather long (too long) system of flex pipes, metal tubing and muffler. We are not happy with it at all. The engine is a bit of a beast, and as a result, the exhaust system rattles and shakes. Rattles and shakes to the point that leaks have developed. We dont think this a problem that can simply be addressed by getting new parts. I'm convinced that the fate of the new parts will be the same in the long run. My opinion is that we will need to switch to a wet exhaust.

I'm wondering if any of you have experience with, or thoughts on matching an air cooled engine with a wet exhaust. The main concern I have is with the length of the exhaust system. In all, it is just under five feet in length, and from what I understand of wet exhausts - the shorter the better. We have no above the waterline seacocks on the port and starboard side of the boat, so the exhaust pretty much has to go out the stern. 

We would love to keep the momentum of our trip going.... but things need to be dealt with.

ANY help would be much appreciated.

Cheers


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## celenoglu (Dec 13, 2008)

Deutz engines run as long as you feed the diesel. They are very reliable but they make a lot of noise. A wet exhaust might decrease the noise but, the engine noise will always be there. Air cooled engines and specially Deutz is always more noisier than a water cooled engine. Try to replace your engine with a water cooled one, otherwise you will not benefit too much from an exhust with water.


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## tommays (Sep 9, 2008)

Its a completely air cooled engine ? 

Its got to get awful hot in there


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## nsweeting (Sep 30, 2011)

Right now, my concern isn't with engine noise. Both of us can manage to live with that. We plan on sailing our boat more than motoring for the most part (unfortunately, January North Atlantic weather dictates otherwise at the moment). Our concern is with the exhaust. Said exhaust leaking into the cabin is not something we can live with (pun intended...).


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## nsweeting (Sep 30, 2011)

The engine is fully air cooled. The duetz is designed that way, and seems to do a good job at it. I have no concern with it overheating. We also have a blower that runs more air to the engine - but this isnt necessary at the moment, as the cool Jaunary air does a good job at that. All we have to do is open a hatch.


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## tommays (Sep 9, 2008)

On the dry section of my exhaust we just wrap the heck out of it to try and keep it at a civil temperature to try and not start a fuel fire should there be a leak


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## JimsCAL (May 23, 2007)

I would think the length of a wet exhaust would be the same as the current dry one. If so, the only way to reduce the pressure loss would be to either straighten it out to reduce bends or increase the diameter. If you went with a new wet system, you would need a small water pump (electric would be the easiest) and a water lift muffler. After the water injection point, you could then use exhaust hose. Seems doable, but you have to consider that the water injection system is going to add some complications and maintenance issues.


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## GaryHLucas (Mar 24, 2008)

Brent Swain has popped up on a thread about Ganley boats in the Review & Purchase forum. If anyone knows how to do this cheap and well, it would Brent.

Gary H. Lucas


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## knuterikt (Aug 7, 2006)

*Wet exhaust should work fine*

You must take the same considerations as on a water cooled engine to prevent water flooding the engine.

I did a similar ting once - this boat originally had dry exhaust going over the wheelhouse roof.

We made a dry muffler that also worked as a water lock (preventing water entering the engine through the exhaust). We welded an water injection bend and attached the flexible rubber exhaust pipe to it. The purpose of this was to 
a) be able to use a flexible rubber exhaust hose 
b) cool the exhaust before going through the hull (wooden boat)

You must look for an arrangement where you can inject water into the system at point w/o risk of back flooding the engine. from that point you can use rubber exhaust hose.

There are flexible tubes around that can be used for dry exhaust - do you have this in your existing system?

Any pictures / drawings showing existing arrangement?


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## SloopJonB (Jun 6, 2011)

I must be missing something here. How does an air-cooled engine get a wet exhaust? Are you talking about pumping raw water from overside into some sort of injection elbow just to cool the exhaust gases?

If that's the case, why bother? I've seen plenty of dry stack exhausts on V8 engine fishboats. Double tubing them and lots of lagging where there might be any contact with anything works just fine - why bother with pumps, through hulls etc?


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## knuterikt (Aug 7, 2006)

SloopJonB said:


> I must be missing something here. How does an air-cooled engine get a wet exhaust? Are you talking about pumping raw water from overside into some sort of injection elbow just to cool the exhaust gases?
> 
> If that's the case, why bother? I've seen plenty of dry stack exhausts on V8 engine fishboats. Double tubing them and lots of lagging where there might be any contact with anything works just fine - why bother with pumps, through hulls etc?


You don't wan't a smoke stack on a sailboat. It's much easier to make a dry smokestack going stright through the roof than through the side of the hull.


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## Ajax_MD (Nov 24, 2009)

If I'm reading your post correctly, it's not the noise you're concerned about, it's that the dry exhaust system shakes apart until it develops exhaust leaks, which are hazardous due to the heat and noxious gasses.

The engine was designed to operate with a dry exhaust, so I don't know if I'd change that. I served on submarines where sound and vibration isolation were absolutely critical to achieve the silence during operation that a submarine requires.

If I were you, I'd investigate installing a vibration dampening system at all of the exhaust system joints, and reducing the number of joints to the absolute minimum. Basically, you're looking at wrapping the tubing in heat wrap to reduce the temperature, and then connecting a circular bracket around it. Then, connect a rubber isolation mount to that, and connect it to a mounting point in the engine compartment somewhere.


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## bljones (Oct 13, 2008)

If your engine is jumping around so much that it causes the exhaust to crack, before I re-engineer the exhaust system I'd look at replacing the engine mounts.
Do you have any pictures of your current installation?


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## captflood (Jan 1, 2011)

GREETINGS EARTHLINGS you say exsaused is to long have you tryed useing one-way flapping valves (this will split the unit up) to exsasepate the back pressure biuld up GO SAFE


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## ewoden (Mar 30, 2011)

Try this for starters:

Good Old Boat - Cool and Quiet and trouble-free article


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## ewoden (Mar 30, 2011)

could also consider a water jacketed system. Water will cool the exhaust run and dampen the vibrations a bit. But this would be pricey fabbing.

Example of jacketing butnote it is without consideration of transom exit and need to preven back flow: http://www.glen-l.com/weblettr/webletters-9/images9/wl75-inb-plate54.gif


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## ewoden (Mar 30, 2011)

Caterpiller has a nice discussion of exhausts for their big diesels. Towards the end are some design ideas and specs for wet exhausts: http://www.gregorypoole.com/product...tor/Documents/LEBW4970-03 EXHAUST SYSTEMS.pdf

Here is the AByC design criteria committee report of marine exhaust system design:
http://www.abycinc.org/committees/P-01.pdf

Silence marine has some figures for aapplications oftheir products.
http://www.silencermarine.com/inglese/silenziatori.htm


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## bljones (Oct 13, 2008)

ewoden, you are missing one big point- the engine is AIR COOLED, not water cooled.


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## nsweeting (Sep 30, 2011)

The system does have some vibration dampening set up. I will try and get some photos later. Basically the system runs horizontally from the engine to the stern of the boat. It goes:

1. exhaust elbow 
2. flex pipe 
3. just some plain metal tubing 
4. muffler 
5. more plain metal tubing 
6. flex pipe 
7. what looks like plumbing tubing that creates the necessary 18 inch above waterline bend - which then exits the stern.

The whole system has a stainless steel shield running along the top wall of the exhaust. From here there are a system of hanging chains which you can connect the exhaust system to. At two points (one before the first flex pipe, and a second before the second flex pipe), there are rubber connection points to dampen the shake more. All of this is wrapped in fibreglass cloth.

2 things that I think are contributing to the leaks:
1. The use of flex pipe.
2. Too many sections.

If I was to try and make the current dry exhaust work, I would need to replace a number of the sections in the exhaust. Right now, it mainly seems to be the flex pipe that begins to crack and leak. We originally got a broken section of it replaced, and it seems to have already developed new leaks. So a big questions is - how necessary is flex pipe in a dry exhaust system? Right now, our funds are not as good as they used to, so any kind of replacement we do will need to somehow be made with off the shelf parts. Not much room for custom welding. Most likely auto exhaust parts. I realize long term, this wont survive the rigors of the ocean air, but it it may get us through the next few months at least. The rubber dampening devices set up seem to work well too - perhaps more of those. 


Any opinions on auto exhaust parts in a dry exhaust system?


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## ewoden (Mar 30, 2011)

bljones said:


> ewoden, you are missing one big point- the engine is AIR COOLED, not water cooled.


How so am I missing anything? Wet exhaust with water pump (belt or electric) would still apply yes? We are not talking about cooling the engine in this case rather cooling the exhaust to allow for a flexible coupling aft or running hot exhaust insulated aft).

You can run a dedicated open loop through sleeved pipe to cool exhaust without mixing and without a lift muffler. (AKA semi wet system). It gets done lots of times, even with air cooled engines.

How does that differ for a water cooled versus air cooled engine? The only issue I can see is running a water pump. That's no big deal, belt feed it like an altenaor just like any water cooled engine or run a dedicated electric pump. Many see advantages to a sleeaved exhaust versus a lift exhaust. Corrosion avoidance being one of them. Such a system would also achieve some measure of vibration damping, and the cost can be kept down by using internal pipe in stainless where the heat is but mild steel on the outside to allow for a more predictable corrosion resistence than one gets with stainless. In the last illustration: http://www.glen-l.com/weblettr/webletters-9/images9/wl75-inb-plate54.gif eliminate vertical stack, put the shebang on an angle to exit 22 inches above water line, replace engine source water with open loop from through hull to pump, to stern throug hull. incorporte other poser's vibration dampers and you are good to go. heck you get downstream to a point where exhaust may be cool enough to use exhaust hose for the final run to the transom. Oh and one avoids the power losses associated with lift mufflers.


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## tommays (Sep 9, 2008)

It would seem the only real issue with the current system is a reliable section of flex as it is the only part that cant be solid 

I would think the longer you can make the flex section the better its ability to deal with the motor movement 

Going to a wet exaust will cause as many issues as it solves at this point


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## Rockter (Sep 11, 2006)

An air-cooled sailboat motor. Now that is a rare one!
The Deutz is a very reliable motor indeed. I have seen them run for incredible hours in the Middle East, in heat you would not believe.
The problem in using one on a sailboat is the enormous appetite they have for cooling air, and the ducting they will need to avoid cooking the cabin. They are a noisy unit, as they lack the water jacket that liquid cooled motors have.
If you wish to run a wet exhaust, then either couple a water pump to one of the pulleys, or perhaps use an electric pump separately. You need to be careful not to pump too much water though, as you can drown the exhaust. Logically, when the motor stops, so too must the electrical pump.

I guess you will never be short of cabin heat when the motor is running!


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## ewoden (Mar 30, 2011)

i'd agree. sounds like the problem here is stabilizing the pipes with adequate lagging and havind a nice stainless woven pipe, like a car for the flexi connection. Given the steel hull, exit temp is not the big concern as for a wooden or glass boat with a hot pipe sticking out the transom. 

Still if water cooling the exhaust flow was a desired feature, and I personally would dig not having real hot pipes running through my boat's interior, one could install an engine fed or electical water pump, and :

1. install a lift muffler and the flexiblehose like bunches of boats and accept the inevitable corrosion from acid production as exhaust gases meet seawater.

2. direct inject water into the exhaust stream down stream (and downhill) from the exhaust manifold (corrosion again)

3. run a jacket around the exhaust pipe filled with flowing raw water with attention to desired angle and perhaps a backflow gate at transom or burble chamber upstream

4. run external copper tubing around the exhaust pipe al la a a glorified heat exchanger (probably not too efficient but might not be bad bedded in slilicon heat sink compound and a wrap of insulation

5. do 3 or 4 but with a keel cooler and expansion valve for safety as a closed loop.


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## ewoden (Mar 30, 2011)

nsweeting said:


> . Right now, it mainly seems to be the flex pipe that begins to crack and leak. We originally got a broken section of it replaced, and it seems to have already developed new leaks. So a big questions is - how necessary is flex pipe in a dry exhaust system? Right now, our funds are not as good as they used to, so any kind of replacement we do will need to somehow be made with off the shelf parts.


stainless mesh flex pipe like this perhaps?
2.25" x 5" Stainless Steel Tripple Mesh Flex Pipe Tube | eBay

Here's another source: http://www.exhaustdepot.net/flexsection.html

This is apparently stainless exhaust bellows tubing wrapped in stainless mesh. Marine versions here: http://www.rosesmarine.com/products_exhaust.html


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## Brent Swain (Jan 16, 2012)

I've used an air cooled engine with a dry exhaust for many years. One diesel Mechaninic was quoted as saying "If everyone went dry exhaust and keel cooling ,us mechanics would all be out of work." Wet exhausts are a major source of engine problems. I met a couple in Tonga who went thru 2 engines since 1996 due to corrosion on valves form wet exhausts. They now have a dry exhaust.
I use sch 40 stainless pipe ,wraped in fibreglass house insulation then aluminium foil, then three inch wide muffler tape, coated with silicone caulking. After days motoring in the tropics ,it feels cool to the touch.
I have experimented with high heat silicone hose. At the head of my air cooled engine, at 3/4 throttler it didn't burn, at full throttle it did. Friends with a water cooled manifold tell me it lasts them 2 years at the manifold, at the transom it has lasted them 15 years with no problem. 
I have a piece clamped on my dry exhaust 2 ft from the head, for a couple of years and it shows no sign of burning , so it appears the trick is to get it some distance form the head. 
One could use the flat wound stainless flex , then silicone silicone hose over it , the stainless to take the direct heat and the silicone to stop any escaping gasses. 
The more solidly mounted the engine, the less flexing your exhaust takes.


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## bljones (Oct 13, 2008)

ewoden said:


> How so am I missing anything? Wet exhaust with water pump (belt or electric) would still apply yes? We are not talking about cooling the engine in this case rather cooling the exhaust to allow for a flexible coupling aft or running hot exhaust insulated aft).
> 
> You can run a dedicated open loop through sleeved pipe to cool exhaust without mixing and without a lift muffler. (AKA semi wet system). It gets done lots of times, even with air cooled engines.
> 
> How does that differ for a water cooled versus air cooled engine? The only issue I can see is running a water pump. That's no big deal, belt feed it like an altenaor just like any water cooled engine or run a dedicated electric pump. Many see advantages to a sleeaved exhaust versus a lift exhaust. Corrosion avoidance being one of them. Such a system would also achieve some measure of vibration damping, and the cost can be kept down by using internal pipe in stainless where the heat is but mild steel on the outside to allow for a more predictable corrosion resistence than one gets with stainless. In the last illustration: http://www.glen-l.com/weblettr/webletters-9/images9/wl75-inb-plate54.gif eliminate vertical stack, put the shebang on an angle to exit 22 inches above water line, replace engine source water with open loop from through hull to pump, to stern throug hull. incorporte other poser's vibration dampers and you are good to go. heck you get downstream to a point where exhaust may be cool enough to use exhaust hose for the final run to the transom. Oh and one avoids the power losses associated with lift mufflers.


 Could you please show me in any of the links you googled and posted where there is any discussion on adding the necessary water pump?

That is my point.

BTW, take a look at the belt drive on a deutz- adding another belt to drive a water pump ain't that easy.


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## ewoden (Mar 30, 2011)

bljones said:


> Could you please show me in any of the links you googled and posted where there is any discussion on adding the necessary water pump?
> 
> That is my point.
> 
> BTW, take a look at the belt drive on a deutz- adding another belt to drive a water pump ain't that easy.


Haha well I can't. But my post was preceeded by one other mentioning the necessity for a pump and indeed one musn't be a naval architect to know that you are gonna need a pumped source of water to run a water cooled anything. Consequently, in the interest ofbuilding the exhaust and not repeating other poster's info/thoughts I figured I'd just help with some plumbing options. Incidentally, I didn't google them for this strings response as I'm building my own and have been toying with an aircooled auxilliary out of cost needs.

Regarding the belt drive, one can always run multiple power robbers with a single belt or is there some ABYC thing against that  . It would be the bracketry that would be the issue from my POV, but all would be moot with a electrically driven pump.


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## nsweeting (Sep 30, 2011)

Brent Swain said:


> I've used an air cooled engine with a dry exhaust for many years. One diesel Mechaninic was quoted as saying "If everyone went dry exhaust and keel cooling ,us mechanics would all be out of work." Wet exhausts are a major source of engine problems. I met a couple in Tonga who went thru 2 engines since 1996 due to corrosion on valves form wet exhausts. They now have a dry exhaust.
> I use sch 40 stainless pipe ,wraped in fibreglass house insulation then aluminium foil, then three inch wide muffler tape, coated with silicone caulking. After days motoring in the tropics ,it feels cool to the touch.
> I have experimented with high heat silicone hose. At the head of my air cooled engine, at 3/4 throttler it didn't burn, at full throttle it did. Friends with a water cooled manifold tell me it lasts them 2 years at the manifold, at the transom it has lasted them 15 years with no problem.
> I have a piece clamped on my dry exhaust 2 ft from the head, for a couple of years and it shows no sign of burning , so it appears the trick is to get it some distance form the head.
> ...


Brent - thanks for your comments. From what I have seen, 500 degrees f seems to be the upper end of the limits of high heat silicone hose. Would I be correct in thinking this?


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## Brent Swain (Jan 16, 2012)

Around there. Yes, 500 sounds about right. You could stick a cooking thermometer under your lagging at various points to get the temperature, when bucking a headwind, or tied to a dock . It cools off a lot the further you get from the engine. I asked my father, a steam engineer, if going from a 1 1/2 inch pipe to a 2 inch would make much difference in exhaust temp. He said " A huge difference."


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## boatpoker (Jul 21, 2008)

I must be missing something here ... the problem is multiple exhasut leaks. How is a water cooled exhaust going to help that ?


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## baboon (Aug 7, 2008)

It sounds like it would be best to try to figure out how to make your dry system work. If you can stand the heat and noise, a dry system has a lot of advantages. Long open water passages can be made with all you seacocks closed, a safety plus. Not intoducing sea water to any part of your engine systems is great, a huge amount of hassels and maintenance are related to wet systems. No strainer to clog, no raw water pump, no impeller to fall apart, no heat exchanger or mixing pot to rust out and cook the motor or flood the boat.

Perhaps you could find some advice on motor boat or trawler forums as these systems seem more common on those craft. Instead of auto parts, tractor or big rig suppliers might be an option as they deal with big motors that move a lot.


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## nsweeting (Sep 30, 2011)

Yeah - I've decided sticking with the dry exhaust seems best. Working with its quirks just takes time. My frustration is mainly with the stainless steel flex pipe, which just seems to not work. It is the only sections in the stack that has developed leaks. 

Between lessening the number of pieces, and not using flex pipe, hopefully something can be made.

I'm also realizing the importance of a solidly mounted engine. This also seems to be lacking a little bit at the moment. The rubber on the mounts seems to be a bit worn, and perhaps not doing as good a job as it should.

Anyone have suggestions on a company that makes good, affordable engine mounts?


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## baboon (Aug 7, 2008)

I do not know a good source for marine mounts, but here is a vid from a guy who used modified car mounts,
ktl 216 film fixing the Beast -pt 1- Alan and Stewy arrive « Keep Turning Left


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## Brent Swain (Jan 16, 2012)

Perko makes the best hard rubber mounts I've seen. I mounted my engine on poly propylene sheets with PVC bushings and washers around the bolts to prevent any metal to metal contact


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## MarkSF (Feb 21, 2011)

captflood said:


> GREETINGS EARTHLINGS you say exsaused is to long have you tryed useing one-way flapping valves (this will split the unit up) to exsasepate the back pressure biuld up GO SAFE


I don't know where to start.


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## MedSailor (Mar 30, 2008)

I, for one like the silicone hose idea. You could use one of these bad-boys to see what your temp is at different spots along the hose.









Infrared Thermometer

Though it sounds like if you had a couple feet of steel pipe near the engine where it is the hottest, then you could run one continuous length of silicone all the way to the stern. No leaks, no flex issues.

MedSailor


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## neverknow (Feb 2, 2011)

Just take your system out and take it to a private muffler shop and have them make it in one pipe. The only flex you will need will be the engine connection.

Any custom exhaust place can do that for you. I wouldn't mess with the chain places Midas, Meinaeke etc. look for a mom and pop place.

It will be important to mark each elbow and pipe so you can reassemble them at the muffler shop. They should also be able to get you a stainless flex engine to exhaust connection. These are used on today's cars to connect the manifold to the exhaust.










Maybe you'll get lucky and find someone who will trade the labor for a sunset cruise on your sail boat. I know most of the small shops around here love to barter. Of coarse you'll still have the cost of the tubing and connector but that's not to much.


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## neverknow (Feb 2, 2011)

MedSailor said:


> I, for one like the silicone hose idea. You could use one of these bad-boys to see what your temp is at different spots along the hose.
> 
> Though it sounds like if you had a couple feet of steel pipe near the engine where it is the hottest, then you could run one continuous length of silicone all the way to the stern. No leaks, no flex issues.
> 
> MedSailor


We use silicone plugs and caps in our powder coating business for masking. The problem with silicone is once it reaches around 600-700 deg. it just turns to ash. No warning at all. So if you get it wrong and any part of the exhaust EVER gets the hot you are completely screwed.

At least with metal you have some warning. You see it glowing or notice it warping. Not so with silicone. It will just be gone......:hothead


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## Stu Jackson (Jul 28, 2001)

Industrial grade flex hose: metraflex


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## Brent Swain (Jan 16, 2012)

MedSailor said:


> I, for one like the silicone hose idea. You could use one of these bad-boys to see what your temp is at different spots along the hose.
> 
> 
> 
> ...


Not when you see the price of silicone hose!
A short piece over flat wound metal flex, with silicone hose over it, is all you need, especially with fairly hard mounts..


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## Capt Len (Oct 9, 2011)

Regardless of how you build this new system,Do you think a CO alarm would be a good addition? All the old fish boats had keel coolers and hot dry exhausts made of common black iron pipe and NPT fittings wrapped in asbestos rope and water glass .Apart from the occasional fire and death from CO poisoning ,worked pretty well. Custom made fiber glass blankets are available and SS pipe/ fittings are cheap at the scrap yard .I once made a complete water jacketed system in SS with bolted flanges and connecting joining hoses ( for a customer). For what it's worth,Thane has a wet exhaust .


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