Reply
 
Thread Tools Display Modes
 
Old 01-13-2016, 09:03 AM   #1
Guru
 
cardude01's Avatar
 
City: Victoria TX
Country: USA
Vessel Name: Bijou
Vessel Model: 2008 Island Packet steadysailer
Join Date: Nov 2012
Posts: 3,167
Wet vs dry exhaust

I have told myself myself over and over that the next boat I buy will have dry exhaust and a keel cooler. It just seems the simplest setup by far, and after working on my little Yanmar I have learned to hate heat exchangers.

However, this seriously limits the possible boats for me to look at. Am I being silly with this requirement?

Are there downsides of a dry exhaust/keel cooling system that I'm missing? There must be since not many boats use this method.
__________________
Advertisement

cardude01 is offline   Reply With Quote
Old 01-13-2016, 09:23 AM   #2
Guru
 
City: Venice Louisiana
Country: United States
Join Date: Dec 2013
Posts: 1,097
Personally, I like dry exhaust/keel cooling. But it is not the best setup for most boats. Read "boat mechanical systems handbook" by Gerr. Then you will be more informed on whether or not its what you really want. Everyone thinks its simpler, but that is not usually the case.
__________________

kulas44 is offline   Reply With Quote
Old 01-13-2016, 09:30 AM   #3
Guru
 
TDunn's Avatar
 
City: Maine Coast
Country: USA
Vessel Name: Tortuga
Vessel Model: Nunes Brothers Raised Deck Cruiser
Join Date: Feb 2015
Posts: 670
There are lots of dry exhaust boats here in Maine. They are pretty much exclusively working boats. The negatives of dry exhaust as I see them are:

1) Noise. Yes it is possible to install mufflers, but they are bulky. Most of the dry exhaust boats I know of are MUCH louder than wet exhaust boats.

2) Soot on deck. No way around this.

3) Heat. Dry exhausts are hot. You need lots of insulation (which does help with the noise) and the exhausts have to pass through the living spaces which takes space. Unless you are talking about a pretty big boat, this can be an issue.

4) Mufflers and dry stacks do burn out potentially leading to exhaust leaks in the living spaces of the boats.

5) There is always the risk of damaging the keel cooler if you hit something. Plus you have an extra hull penetration that is hot which makes it harder to seal and keep sealed.

6) Repairs will be pretty expensive potentially requiring significant surgery in the boat's interior.

Frankly a wet exhaust system is not at all complex.
TDunn is offline   Reply With Quote
Old 01-13-2016, 09:40 AM   #4
Guru
 
SCOTTEDAVIS's Avatar
 
City: Vero Beach, FL.
Country: US
Vessel Name: FIREFLY
Vessel Model: Pilgrim 40
Join Date: Nov 2012
Posts: 913
Quote:
Originally Posted by cardude01 View Post
I have told myself myself over and over that the next boat I buy will have dry exhaust and a keel cooler. It just seems the simplest setup by far, and after working on my little Yanmar I have learned to hate heat exchangers.

However, this seriously limits the possible boats for me to look at. Am I being silly with this requirement?

Are there downsides of a dry exhaust/keel cooling system that I'm missing? There must be since not many boats use this method.
Dry exhausts while having many advantages have some rather significant disadvantages, they take up a lot of room in order to have clearances needed to prevent fires. This space is generally taken from right in the middle of the boat from the engine room all the way vertical to way above the top deck. Due to the large mufflers needed to keep the noise to a reasonable level this is a rather large waste of space for many designers. They are dirty leaving deposits and soot flakes all over the deck of your boat and others in the marina. You find them in more often in large commercial boats where these disadvantages are not as great a problem.

Keel cooling on the other hand is a great option and has no real disadvantages that I can think of with the possible exception of damage from a grounding, however with proper design and location that can be minimized to a near non-issue.

I think a hybrid system using raw water to cool the exhaust system not including the headers. With keel cooling for the engines and manifolds would be the cats azz.
SCOTTEDAVIS is offline   Reply With Quote
Old 01-13-2016, 09:46 AM   #5
Guru
 
cardude01's Avatar
 
City: Victoria TX
Country: USA
Vessel Name: Bijou
Vessel Model: 2008 Island Packet steadysailer
Join Date: Nov 2012
Posts: 3,167
Quote:
Originally Posted by SCOTTEDAVIS View Post
I think a hybrid system using raw water to cool the exhaust system not including the headers. With keel cooling for the engines and manifolds would be the cats azz.

Yeah that would be a good setup. Don't know if I've seen that on a boat.
cardude01 is offline   Reply With Quote
Old 01-13-2016, 10:43 AM   #6
Senior Member
 
Portage_Bay's Avatar
 
City: Seattle
Country: United States
Vessel Model: Tollycraft 40 Tri-cabin
Join Date: Oct 2015
Posts: 150
With the perspective of a lifetime of working on dry stack boats along with much more limited ownership of wet exhaust recreational boat I can say that the previous posters have hit the main points.

Noise is solvable but it costs $$$ and space. Most work boat owners don't care about noise so that is why they are so noisy.

Soot is not solvable with an older engine. The make soot. The newer tier 3 engines might be better.

Fire is not really a worry if the system is built right and well maintained. 46 yrs on the water, dozens of different boats, new, old and really old. Never an exhaust fire or leak. Ever.

Interior volume lost in unavoidable. For a 40' trawler single engine I'd think along the lines of the depth and width of a full sized fridge from the engine room to the upper deck, then the same amount some distance above the deck, then stacks going higher. All right over the aft end of the engine.

One thing not mentioned is exhaust gas flow. Look at the work boats and you will notice the stacks are high and on some angled to the side. This is because the air flow on a moving boat in relatively clam air is forward from transom to bow. If the stacks are not high enough the gasses flow down onto the deck the forward into the house. Been there, it's miserable.

Keel cooler damage from grounding is easy to solve. Build a pocket for the cooler next to the keel, this will protect from all but the most destructive groundings in which case you will have a lot more to worry about than keel cooler damage.

It's hard for me to see the advantage of a keel cooler + wet exhaust system. You'd have the complications of both systems.

If money were no object and I could have exactly what I want my architect / engineer would be asked to design a dry stack for me. But the reality is I like most I buy used boats. Most recreational boats are wet exhaust.

I like dry stack because in my opinion it is over all safer, less to worry about and without any data to back it up I think dry stack increases engine life. Unless your engine crawl space has the vertical clearance for a high riser you will introduce moisture to the exhaust valves.
Portage_Bay is offline   Reply With Quote
Old 01-13-2016, 11:18 AM   #7
Guru
 
twistedtree's Avatar
 
City: Gloucester, MA
Country: USA
Join Date: Jan 2013
Posts: 3,185
Quote:
Originally Posted by TDunn View Post
There are lots of dry exhaust boats here in Maine. They are pretty much exclusively working boats. The negatives of dry exhaust as I see them are:

1) Noise. Yes it is possible to install mufflers, but they are bulky. Most of the dry exhaust boats I know of are MUCH louder than wet exhaust boats.

2) Soot on deck. No way around this.

3) Heat. Dry exhausts are hot. You need lots of insulation (which does help with the noise) and the exhausts have to pass through the living spaces which takes space. Unless you are talking about a pretty big boat, this can be an issue.

4) Mufflers and dry stacks do burn out potentially leading to exhaust leaks in the living spaces of the boats.

5) There is always the risk of damaging the keel cooler if you hit something. Plus you have an extra hull penetration that is hot which makes it harder to seal and keep sealed.

6) Repairs will be pretty expensive potentially requiring significant surgery in the boat's interior.

Frankly a wet exhaust system is not at all complex.
This pretty well nails it, but I'd add one or two minor points.

Keel coolers need to be kept clean or their ability to transfer heat becomes impaired. This isn't a huge issue, but does require attention along with bottom and prop cleaning.

Soot sucks. I've got a tier 3 engine and although I don't get flakes of soot on the boat, I do get blackening of the upper stack and surrounding gear. Cleaning soot off your transom is MUCH easier than washing down a stack and instruments 30' off the ground.

So now having owned both types of boat, I think it's a nearly even trade off between the two. Just pick your poison.
__________________
www.MVTanglewood.com
twistedtree is offline   Reply With Quote
Old 01-13-2016, 11:49 AM   #8
Guru
 
djmarchand's Avatar
 
City: East Greenwich, RI
Country: USA
Vessel Name: Bella
Vessel Model: Mainship Pilot 34
Join Date: Aug 2012
Posts: 2,875
All of the above comments are correct. The only production recreational "trawler" that I know of that has a dry exhaust is the Nordhavn. So yes, it will very significantly limit your choices if you insist on a dry exhaust.


Also forget about trying to retrofit a dry exhaust on a wet exhaust boat. You need a 1'x1' vertical chase for the exhaust line. I don't want one of those in the middle of my galley, salon, etc.


David
djmarchand is offline   Reply With Quote
Old 01-13-2016, 12:17 PM   #9
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 3,882
Also some provision must be made to keep rain out of the stack pipe. If not, rain gets in there and rusts things out, and also when engine is cranked up it will spew sooty water out. Nasty!!

Regarding engines, one of the major benefits of DS and KC is it gets rid of any SW plumbing related to the engine. The "hybrid" system carries the SW downside into an otherwise elegant system.

Another complication is many modern engines come factory with SW aftercoolers and changing that design to FW aftercooling is difficult without creating a plumbing mess. Not many JWAC options out there. That's jacket water after cooler.

Still have a lot of love for dry stack.

Downeast boats are hard to build with a wet mixer high enough to keep water out of the engine. Engines mount low in the keel belly and builders like the deck right on top of the engine. So where to put an elevated mixer??? Hard to do. So that is one reason for the popularity of DS on DE boats, especially working boats where buying engines to replace water logged ones has a big effect on the bottom line!!
Ski in NC is offline   Reply With Quote
Old 01-13-2016, 02:14 PM   #10
Guru
 
refugio's Avatar
 
City: Meydenbauer Bay Yacht Club
Country: USA
Vessel Name: Refugio
Join Date: Mar 2012
Posts: 1,141
My old Romsdahl was keel-cooled, dry stack. But a keel cooler on a steel hull is just a bunch of tubing cut in half.

My current vessel started life as a dry stack and then had a fire - there's still some charred wood in the overhead of the pilothouse. Since that's over the FRONT end of the engine, I dunno how it was plumbed but it must have been ugly.

But that was removed and a wet exhaust with a giant hydrolift in the engine room was installed before I purchased it. The cutout core in the transom came with the boat - it's great for showing someone how the hull is constructed!

Then a few years back I added a large Salisbury Hydrovac Exhaust Silencer, which effectively changed my above-water exhaust into a below-water exhaust. A little bit quieter, much less exhaust smoke under way, but I end up with some soot on the transom that I have to periodically scrub off.

I moor in freshwater and operate there much of the year, so I don't get much growth in the cooling system and zincs last a long time.

And I was able remove the cabinetry in the galley and create a storage locker, and in the pilothouse to create a giant-size berth. Huge win for me in livability for the 90% of the time I'm on the boat with the engine not running.
refugio is offline   Reply With Quote
Old 01-13-2016, 03:38 PM   #11
Guru
 
C lectric's Avatar
 
City: Somewhere
Country: , Canada
Vessel Name: Island Pride
Vessel Model: Palmer sedan 32'
Join Date: Oct 2007
Posts: 1,864
I agree with all the points made that A dry stack system is not a panacea. I have had this discussion on the dock with a few people over the years and basically it's not worth the change of an existing boat and often simply not possible without destroying the boat. However, after living with one for the last 30 years and with wet exhaust before that I am ok with my system.

It is a dry stack with a heat exchanger for the engine cooling. It works fine.

--Yes, water must be kept out of the stack when not in use. Not a big deal to make a cover. Mine is a piece of 6" pvc pipe which I then painted white and attached a tube for a handle. That cover is on anytime the engine is not running unless the weather is clear and dry.

--both system can eat up a bunch of space but I agree less with a wet. However read Boatdiesel for all the guys who lunch turbos because of a crappy wet system. There is no free lunch which ever system you have if it is done poorly.

--soot on deck. Yup, i used to get that untill I repitched the prop so the engine was under less load at the same revs. More air throughput and higher exhaust volume has kept things good for now ~8 years. ALso a lot of idling or short start/stop type runs will increase the odds of soot.

--exhaust runs do not always have to go through the cabin. Mine runs to the back deck and then up which is also where the mufflers are, in the vertical stack. But then I have a smaller boat at 32 ft so it was not difficult to setup when the boat was being built.

--Noise. Yes my boat is noisier than a comparable vessel with a wet system. It's not bad but it is not quiet. I will partly blame the engine location which is right under the salon.

--Cost., Not sure I agree here. Yes I had to do a $5K repair about 20 yrs ago but that was mostly because the tubing was too light in the first place. NOt the systems fault but the builder.

--Access. Mine runs through the engine compartment under the back deck and then up with the mufflers in the vertical shroud/cover so access is good. However with other vessels that would have to be a serious consideration. If the system runs through the main cabin or otherwise cuts the living area up then that would not be so attractive.

--Most recr. boats have a wet system for a reason that is valid.

So if you are thinking about a dry system be aware of all the angles. There is no free lunch. For a pleasure boat I would say the wet has the edge unless you simply want it, the dry, and the system does not cut up the boat.
C lectric is offline   Reply With Quote
Old 01-13-2016, 04:10 PM   #12
Guru
 
cardude01's Avatar
 
City: Victoria TX
Country: USA
Vessel Name: Bijou
Vessel Model: 2008 Island Packet steadysailer
Join Date: Nov 2012
Posts: 3,167
Wet vs dry exhaust

The boat with a dry exhaust I'm most interested in would be on a Nordhavn. Maybe they are engineered well enough to overcome some of the negatives?
cardude01 is offline   Reply With Quote
Old 01-13-2016, 04:42 PM   #13
Guru
 
ranger42c's Avatar
 
City: Maryland
Country: USA
Vessel Model: 42' Sportfish
Join Date: Aug 2013
Posts: 3,156
Quote:
Originally Posted by cardude01 View Post
I have told myself myself over and over that the next boat I buy will have dry exhaust and a keel cooler. It just seems the simplest setup by far, and after working on my little Yanmar I have learned to hate heat exchangers.

However, this seriously limits the possible boats for me to look at. Am I being silly with this requirement?

Are there downsides of a dry exhaust/keel cooling system that I'm missing? There must be since not many boats use this method.

Ummm... shopping again, already??

Anyway... maybe easiest to come to terms with your heat exchanger. What's the issue with that?

-Chris
__________________
South River, Chesapeake Bay
ranger42c is offline   Reply With Quote
Old 01-13-2016, 05:03 PM   #14
Veteran Member
 
City: Toledo
Country: USA
Join Date: Dec 2015
Posts: 86
Quote:
Originally Posted by cardude01 View Post
The boat with a dry exhaust I'm most interested in would be on a Nordhavn. Maybe they are engineered well enough to overcome some of the negatives?
Nordhavn are big proponents of the dry exhaust and presumably after all this time have gotten pretty good at it. However, I do know that they will build wet exhaust to customer preference (I think Ken Williams Sans Souci has a wet exhaust..). Personally, I would be more concerned about a poorly engineered exhaust wet or dry than a tested well designed of either.
devorenm is offline   Reply With Quote
Old 01-13-2016, 06:23 PM   #15
Guru
 
cardude01's Avatar
 
City: Victoria TX
Country: USA
Vessel Name: Bijou
Vessel Model: 2008 Island Packet steadysailer
Join Date: Nov 2012
Posts: 3,167
Wet vs dry exhaust

Always shopping it seems. 😳

No issues with the current HE-- just thought the dry exhaust and keel cooler would be the best set up, although that doesn't really seem to be the case.
cardude01 is offline   Reply With Quote
Old 01-13-2016, 07:13 PM   #16
Master and Commander
 
markpierce's Avatar
 
City: Vallejo CA
Country: USA
Vessel Name: Carquinez Coot
Vessel Model: 2011 Seahorse Marine Coot hull #6
Join Date: Sep 2010
Posts: 10,251
Sounds like wet exhaust is much simpler.

__________________
Kar-KEEN-ez Koot
markpierce is offline   Reply With Quote
Old 01-13-2016, 08:15 PM   #17
Guru
 
City: Venice Louisiana
Country: United States
Join Date: Dec 2013
Posts: 1,097
A poorly designed wet exhaust is better than a dry exhaust everytime. A well designed dry exhaust on a boat designed for it is very hard to beat.
kulas44 is offline   Reply With Quote
Old 01-13-2016, 09:38 PM   #18
OFB
Guru
 
OFB's Avatar
 
City: Richmond bc
Country: Canada
Vessel Name: Invader no1
Vessel Model: Kishi Boat works
Join Date: Mar 2012
Posts: 636
Love my dry stack , Keel cooled set up. Tractor engine on frames dropped into a boat. The DD is in a garage when not in use.

Build the exhaust , insolate it, bolt the cooler to the bottom of the boat and its a done deal.

WHATS NOT TO LIKE.

3288 bayliner be perfect compared to the cost of replacement on original.

Dudes it what it is !!!!!

Be a great INPROVEMENT on the likes of a 36 grand banks IMO. as a live aboard I could use the storage created <

( Grin )

Turbo ??? ya not such a great idea.
OFB is offline   Reply With Quote
Old 01-14-2016, 12:19 AM   #19
Guru
 
City: Doha
Country: Qatar
Join Date: Jun 2012
Posts: 663
[QUOTE=SCOTTEDAVIS;404033]Keel cooling on the other hand is a great option and has no real disadvantages that I can think of with the possible exception of damage from a grounding, however with proper design and location that can be minimized to a near non-issue.QUOTE]

The shipyard I am working with proposed the same system they use on tugboats, which is a keel cooler protected by a steel barrier. This would work for a fiberglass or wood boat as well. Since my vessel is low hp in comparison, I specified just split pipe welded to the hull.
Attached Images
 
makobuilders is offline   Reply With Quote
Old 01-14-2016, 07:39 AM   #20
Guru
 
City: Satsuma FL
Country: United States
Vessel Name: No Mo Trawla
Vessel Model: Hurricane SS188
Join Date: Jul 2014
Posts: 1,672
Quote:
Originally Posted by cardude01 View Post
Always shopping it seems. 😳

No issues with the current HE-- just thought the dry exhaust and keel cooler would be the best set up, although that doesn't really seem to be the case.
Hey cardude, you got your boat up for sale?

2008 Island Packet PY Cruiser Power Boat For Sale - www.yachtworld.com
__________________

Donsan is online now   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 11:55 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012