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Old 02-25-2014, 08:03 AM   #1
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Disadvantage of dry stack/keel cool?

Well here goes another question...

Being new to boats i can't help but ponder why more recreational boats aren't keel cooled and dry stacked. It seems that i would eliminate both cost, complexity and maintenance. I know Nordys are...and probability other passagemakers too. But why not your run of the mill production boats?

What got me thinking about this is that i am considering a repower from my Albin. I had been having some issues with finding parts for my Nissan Diesel. I have an inside connection for industrial/ag Kubota and Deere engines but they are not marine versions.

The only thing i can see is it may be a slight bit of an issue routing the exhaust pipping. I am assume that the after the manifold the pipe is some sort of double wall insulated pipe so it can be ran safely up and out of the vessel. Hardly seems like rocket science.

As for the engine cooling, I have looked at pictures and saw a few boats where the keel cooler is a radiator looking thing specifically made for the job. I have also saw a few where it looks like copper tubing running along the keel. So long as it tucked up where it is unlikely to get slammed by debris or hit during a grounding i don't see why any problems with refitting a boat with either system.

Seems to me that by eliminating an entire system (raw water) it would be both cost effective and reliable. Not to mention opening up more engine choices.
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Old 02-25-2014, 08:07 AM   #2
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Soot, but it's not that bad.
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Old 02-25-2014, 08:17 AM   #3
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Keel cooled boats must have an air cooled chase for the exhaust all the way through the upper dock. Limits layout on most boats.

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Old 02-25-2014, 08:25 AM   #4
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By air cooled chase...do you mean it is a double wall pipe that has some sort of forced ventilation between the walls of the pipe?
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Old 02-25-2014, 08:32 AM   #5
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Dry stack is probably rare simply due to cost, noise, soot, interior space, risk of stack fires (inside muffler).. Fiberglass pipe and rubber hose is easy to run with little fire risk. Dry stack needs an insulated (fire proof) passage for the pipes and muffler. A stack up near flybridge will be noisy unless you use a very good muffler. Soot particles spit out and land on deck making a mess.

But no doubt, there is the "coolness factor". I have run a couple dry stack boats and always liked them. One was super loud (detroit 453), the other was quiet (big boat, stack far away from helm. Liked running both.

Keel cooling is also a good way to go. The 453 used redneck copper pipes along the keel. It was about 40yrs in service with apparently little to no maintenance. Worked fine. The other was steel hull with cooling passages welded into hull. Also worked fine.

You will be limited in marine engine choices should you go that route. High output engines use sea water for turbocharger aftercooling, no easy way to retain that system with keel cooling. Many industrial engines use coolant for aftercooling, those will be easy to install.

Dry exhaust manifolds used on industrial engines do present a fire risk in boats (just investigated one last year). It is a real risk and might get you some trouble getting insurance.
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Old 02-25-2014, 09:59 AM   #6
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You could add a marine exhaust manifold

You could add a marine exhaust manifold and go dry from there up. I had a friend with a a 36' double ender with a dry stack. He used the chase around the dry stack as heat for the helm. He had added little opening vents that convected warm air. At the time we really appreciated the heat. I don't think we gave CO poisoning any thought. Somtimes you just get lucky.
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Old 02-25-2014, 10:03 AM   #7
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Not all Nordhavns are dry stack. It is a buyers option to go wet exhaust. Soot and high end yacht finishes are a poor mix. Soot on neighboring vessels is a concern especially with older diesels.

IMHO, for normal cruisers, when adding up pros and cons , from a non soot standpoint, it really comes down to personal preference with no decided advantage one way or another. But if you are in a fast boat hull drag is a consideration or an outright no no.

For commercial fishing vessels, dry stack is great as no concern as to water level is required, until of course you are about ready to sink - think dry stack in the movie Jaws.
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Old 02-25-2014, 10:22 AM   #8
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Soot, but it's not that bad.
Sure... now ask the guy downwind of you how bad!

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Old 02-25-2014, 11:18 AM   #9
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18 gallons of coolant.
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Old 02-25-2014, 11:40 AM   #10
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Space would be the big limiter for me.
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Old 02-25-2014, 11:48 AM   #11
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Sure... now ask the guy downwind of you how bad! Dave
That was a good one Dave!

The dry stack soot is actually pretty easy to control. I'm sure you've seen the commercial fishing boats with a bucket over their exhaust stack to prevent rain from entering. If you keep the rain out, you will almost never soot (the rain washes the soot down the pipe and that is typically what gets blown out).

Periodically running the engine well loaded also significantly reduces the possibility of soot accumulation. Although having a dry stack does make you a little more aware of which way the wind is blowing when you start the main engine.
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Old 02-25-2014, 12:33 PM   #12
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Sure... now ask the guy downwind of you how bad! Dave
We very rarely have soot shoot out on start up, it's mostly when we run WOT the last minutes of a trip before coming into a marina or anchorage.
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Old 02-25-2014, 12:36 PM   #13
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Dry stack is probably rare simply due to cost, noise, soot, interior space, risk of stack fires (inside muffler).. Fiberglass pipe and rubber hose is easy to run with little fire risk. Dry stack needs an insulated (fire proof) passage for the pipes and muffler. A stack up near flybridge will be noisy unless you use a very good muffler. Soot particles spit out and land on deck making a mess. But no doubt, there is the "coolness factor". I have run a couple dry stack boats and always liked them. One was super loud (detroit 453), the other was quiet (big boat, stack far away from helm. Liked running both. Keel cooling is also a good way to go. The 453 used redneck copper pipes along the keel. It was about 40yrs in service with apparently little to no maintenance. Worked fine. The other was steel hull with cooling passages welded into hull. Also worked fine. You will be limited in marine engine choices should you go that route. High output engines use sea water for turbocharger aftercooling, no easy way to retain that system with keel cooling. Many industrial engines use coolant for aftercooling, those will be easy to install. Dry exhaust manifolds used on industrial engines do present a fire risk in boats (just investigated one last year). It is a real risk and might get you some trouble getting insurance.
Noise depends on muffler, ours is super quiet at 1900 RPM (7.3 Kts).
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Old 02-26-2014, 07:20 AM   #14
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The advantages of keel cooled and dry stack are immense, but not all folks can use them.

No winterizing , with no heat needed on the boat , except perhaps a block heater to start at -30F.

No engine loss . sinking ,fear if the power goes off for a few weeks at the marina.

Any engine can be installed that has a SAE bell housing , so getting away from marine BS can lower replacement engine cost to minor.

The constant need to filter seawater and replace impellers is not needed.

An area for the exhaust , exhaust tubing run inside a std fire place SS exhaust flue is cheap and can be used to have a drying hanging locker.

It does take a slight bit of talent on the part of the NA to fit the dry exhaust into the interior if desired..
Ours runs external with no SS covering .

Otherwise I find no downside

The exhaust noise can be reduced to very low by installing an external Hospital Critical style silencer , these are not cheap, but can be found used.
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Old 02-26-2014, 08:33 AM   #15
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The maintence on the keel cooler is very easy. I dove boats here on the gulf coast for years. A mask/air and chain. Wrap the chain around the tubes and saw the barnicles off. My dry stack is basically a small 2'x2' shut running behind the bathroom that was lined with I assume some sort of fire retardant panels. I couldn't tell they were burnt up. I will be replacing that soon. The mufflers where fab'd in a local welding shop from large diameter pipe. My only issue is when cranking at the dock with the wind blowing aft-stern I get smoke back from the pipes. The po had towels stuffed in the exhaust pipe liner. Not a good idea I would imagine.
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Old 02-27-2014, 06:30 AM   #16
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A disadvantage for us is the stack is the highest point on the boat , so needs to be measured with great care,

We are 12ft 6 inches and motor under 13 ft bridges as required.

An old fiberglass antenna at the bow is the measure if we get close , it fits , we fit.

Coastal cruising can be a big PIA if one has to wait for bridge openings , might as well have a sail boat!
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Old 03-01-2014, 03:44 PM   #17
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Dry stack sounds good to a lot of folk. It can be a problem at times though.
Takes up deck or cabin space, sooting can be a problem, takes up engine room space, noisier usually, adds height to the boat, if not built right won't last and can be expensive to re&re., Stack fires can occur.

I realize much above applies to any exhaust system.

Double walled pipe is not necessary. A GOOD, WELL DONE BLANKET will do a good job and if/when a problem crops up can easily be removed/repaired/replaced also to allow piping repairs.

How do I know - I have one. Would I dump it - no.

Not all the potential problems can be avoided but most can.

My boat was built with it, not a conversion. Not all vessels can be easily refitted due to many factors.

Just don't go into it with stars in your eyes as a cure all. It will fix some things and cause other problems. If not done well can be dangerous.

Can;t comment on the keel cooling as i don't have that.
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Old 03-02-2014, 12:58 PM   #18
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Keeping salt water out of the boat - priceless.

No raw water pumps.
No expensive unique marine manifolds
No through-hulls for the engine
No strainers
Way less heat exchanger maintenance

Vs some soot?
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Old 03-02-2014, 01:21 PM   #19
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Old 03-02-2014, 07:15 PM   #20
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And it's not like wet exhaust boats don't soot up. It just ends up on the sides and transom instead of the deck.
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