Wet vs dry exhaust

Our N62 Nordhavn is somewhat unique,,, keel cooled, wet exhaust.
Best of both worlds in my opinion.

As you can see though,,, there are many opinions/experiences out there,,, and they all make sense. You just have to individually choose which keeps your powder dry.

However, my final input,,,If I ever get to build a N76, it will be twin engined, keel cooled, wet exhaust.

I like the keeled cooled system, just dont understand going wet exhaust. You still have all of the things that most folks dont like, raw water pump, rubber and fiberglass, saltwater. I dont get it. The ONLY reason for dry exhaust/keel cooling is, IMO, on a pleasure boat, to get rid of the saltwater and associated pumps/plumbing.

kulas44 said:

I like the keeled cooled system, just dont understand going wet exhaust. You still have all of the things that most folks dont like, raw water pump, rubber and fiberglass, saltwater. I dont get it. The ONLY reason for dry exhaust/keel cooling is, IMO, on a pleasure boat, to get rid of the saltwater and associated pumps/plumbing.

Click to expand...

Not so.
The P.O. told me he had flooded several engines on previous boats backing down when fishing and said never again. His problem was not the heat exchanger/plumbing setup.
The boat was intended as a planing boat so the keel cooler was not practical. When the hulls were fitted out as actual fishing boats, trollers or gill netters, they usually did have the keel coolers.
I got the boat when they realized they didn't install enough HP and it could not achieve the speed they wanted so they sold it.
I run it at between 7 & 8 knots. They wanted ~14-15.

Some other vessels did get those speeds but with at least another 75 hp and in one case big time mods. to the keel and hull.

After working and running dry stack boats and living and traveling on a wet exhaust boat I prefer the dry stack a heck of a lot more the space one gives up for the dry stack rising from the ER to the stack is negligible compared to the benefit for the engine.

The engine does not know if it's running on a tractor, a truck or in a boat in the dry stack configuration and as has been stated before the keel cooling works very well.

The negatives of covering the exhaust with a sock to stop rain entering the stack after use, as well as soot blowing to other boats upon start up is so minor compared to the benefits........

Go dry any day

gwkiwi said:

Go dry any day

Click to expand...

So when will you convert your DeFever to dry stack?

sunchaser said:

So when will you convert your DeFever to dry stack?

Click to expand...

Not soon is my guess

http://www.curtisstokes.net/trawler-for-sale-defever49-takes-two.html

You still have all of the things that most folks dont like,"

THE BIG THING TO NOT LIKE IS THE DANGER OF FLOODING THE ENGINE

How many folks carry at least 3 engine oil changes , so a flooded engine can be brought back into service?

FF said:

You still have all of the things that most folks dont like,"

THE BIG THING TO NOT LIKE IS THE DANGER OF FLOODING THE ENGINE

How many folks carry at least 3 engine oil changes , so a flooded engine can be brought back into service?

Click to expand...

Geez FF, with millions of wet exhaust vessels out there at least a few figured out a century ago how to make wet exhaust systems work right. How many sailboats do you see with dry exhaust, the very vessels you, I and many have chosen for blue water work.

The dry exhaust requirement from the commercial side serves a very different need - continually variable waterline.

On a pleasure craft either way can work. On a dry exhaust system in the tropics one better have lots of ER cooling fan capacity. And then there is soot. I've heard many dry exhaust boat owners say soot isn't an issue for them - then I tour their top sides. Ugh. Know a Nordhavn owner who ripped out his dry stacked Series 60 as it was a real sooter. Replaced it with a JD with much less soot, but not zero.

Dry stack on a larger high end pleasure craft is non existent, why is that? For those with 60 something Ns forgive me.

So Dude, dream away. That million dollar plus N can be found with dry stack, but even Nordhavn has trouble explaining why they are superior. Their new CP 59, the Fleming fighter, is wet exhaust of course. Could you imagine the Fleming boys pointing out a stack on the CP 59?

To me a big deal is having just a little bit of "stack talk". Call me weird, whatever. On one DS I set up I got the muffler just right and you could hear the engine note. A diesel running at low rpm makes a pleasant tone.

On another with a DD we put what we thought was a good muffler and that thing was still too damn loud. Running at hull speed, it was ear muff time on the back deck, and even in the pilot house unless pilot house doors were shut. Owner did not want to revisit the muffler so it is what it is. DD's are notoriously hard to make quiet, and that one was a 4-53 which is worst of the worst.

On my boat I went with wet, and did the best job I could do building the water lift muffler. Well I get zero "stack talk", if you can call it that with wet. I know that Cummins at 950 really sounds good from other boats with lesser mufflers, and I can't hear anything!!

We do have a couple SF boats with straight pipes, one has two of my same engine. It sounds great. For about five minutes, then it is like a Harley. Too dang loud. But sounds great barking the motors while maneuvering. Fun!! But a long run at 2100 and I'm looking for ear muffs.

Wet exhaust just reminds me of some animal with severe gastronomic distress. But for most boats it is more practical.

Driving a Camry is also practical, but where's the coolness factor there??

Ski in NC said:

Driving a Camry is also practical, but where's the coolness factor there??

Click to expand...

Well Ski, I've been told driving a non noise Tesla is cool too.

I own a sportfisher, and it will back up faster than a trawler will go forward. NEVER, not once have I flooded an engine. It has 10 inch exhausts exiting the transom at the waterline. When backing down they are completely underwater, sometimes by about 3 feet. I have friends with big sporties and run in circles of people that also have them. I still have not heard anyone say they flooded an engine backing down. I'm calling BS, its an age old "wifes" tale. But I could be wrong

Here in South Florida and the Keys (and a lot of other places too) where we have a few sportfishers what has been pretty much standard operating procedure for decades is the installation of surge tubes to prevent backflooding while backing down. Another consideration is how high above the waterline your riser is. If your riser is 2ft above the waterline you will have a lot less chance of backflooding than if it's 1ft. A lot of variables when it comes to back flooding

Back flooding can also happen when docked and the wind shifts to pushing waves up the stern, not just from backing down. 10 or 12 hours of 1ft waves hitting the transom can work it's way up an exhaust system at an alarming rate.

kulas44 said:

I own a sportfisher, and it will back up faster than a trawler will go forward. NEVER, not once have I flooded an engine. It has 10 inch exhausts exiting the transom at the waterline. When backing down they are completely underwater, sometimes by about 3 feet. I have friends with big sporties and run in circles of people that also have them. I still have not heard anyone say they flooded an engine backing down. I'm calling BS, its an age old "wifes" tale. But I could be wrong

Click to expand...

kulas44 said:

I own a sportfisher, and it will back up faster than a trawler will go forward. NEVER, not once have I flooded an engine. It has 10 inch exhausts exiting the transom at the waterline. When backing down they are completely underwater, sometimes by about 3 feet. I have friends with big sporties and run in circles of people that also have them. I still have not heard anyone say they flooded an engine backing down. I'm calling BS, its an age old "wifes" tale. But I could be wrong

Click to expand...

Fair enough. I have only told you what the PO told me. Whether or not it was BS I cannot say.

Water won't back up into wet exhaust with engines running. You've got a dang powerful air pump that doubles as an engine pushing exhaust OUT. Nothing goes backward into turbo with the engine on. Backing down or whatever.

But come in from offshore on a rough day with low risers and one dead engine and then you can have trouble. Or a rough storm tied to a face dock, seas on the ass. Or grounding and boat leans over. I have recovered flooded engines from all three of those events, and probably some I can't think of.

It does happen. But not if engine is running.

Not even talking gennies here, I have unsunk literally hundreds of those.

Lots of commercial guys while anchored in rough stuff fishing leave engine on just to keep the water out.

Now where the heck is my framing crew???!!!

Aye. That makes more sense. I likely changed the story a bit since I bought the boat over 30 yrs ago. Maybe an engine quit and he flooded it. I don't know but he did say it was flooded.

Not having experienced dry stacks, gurgling wet exhaust sounds good.

I suppose it depends on how well integrated and designed the dry stack/keel cooler is to the vessel. Our keel cooler is protected by steel fins. I've hit lots of logs and rubbish and never any damage. The dry stack is quiet with a Cowl muffler and other than the odd flake of carbon, far cleaner than transom exhausts I have had. Loss of space? I guess so, and on our boat maybe 12 cu feet. However, that raceway is where we mounted the Dickinson heater and I am hard pressed to think how the liveability of the boat would be improved without that modest use of interior volume. Rain intrusion? Not a tough problem to solve, even without rattling stack covers.

The upside? No cooling failure due to impellers coming apart. No sea water water inside the boat. No gurgling, splashing, belching water. No transom soot. To each his own, I guess.

"The upside? No cooling failure due to impellers coming apart. No sea water water inside the boat. No gurgling, splashing, belching water. No transom soot"

And the ability to let the boat cold soak, no draining or flushing antifreez into the sea water side.

Below freezing ? , tie to the dock and walk away.

For most TT folks a power failure on the dock will require lots of work winterizing the boats fresh water tanks , pumps , hw hearer and sump pump , but no special care will be required for the engine , or noisemaker if it is properly done too.

FF said:

For most TT folks a power failure on the dock will require lots of work winterizing the boats fresh water tanks , pumps , hw hearer and sump pump , but no special care will be required for the engine , or noisemaker if it is properly done too.

Click to expand...

Some on TF boat where freeze ups are not a concern. Also, it seems winterizing a dry stack is a must if the vessel is in a freezing climate to take care of the non main propulsion engine items you just mentioned.

Delfin said:

I suppose it depends on how well integrated and designed the dry stack/keel cooler is to the vessel. Our keel cooler is protected by steel fins. I've hit lots of logs and rubbish and never any damage. The dry stack is quiet with a Cowl muffler and other than the odd flake of carbon, far cleaner than transom exhausts I have had. Loss of space? I guess so, and on our boat maybe 12 cu feet. However, that raceway is where we mounted the Dickinson heater and I am hard pressed to think how the liveability of the boat would be improved without that modest use of interior volume. Rain intrusion? Not a tough problem to solve, even without rattling stack covers.

The upside? No cooling failure due to impellers coming apart. No sea water water inside the boat. No gurgling, splashing, belching water. No transom soot. To each his own, I guess.

Click to expand...

Nice to see you Carl. The Delfin couldn't be more perfect and is well suited and designed for a dry stack arrangement. The pleasure boating world is filled with nice dry stack arrangements whether a Nordhavn or Diesel Duck. These newer designs owe their chops to the North Sea designs, Delfin being the perfect example.

Recently became aware of the cost to replace antifreeze on a Nordhavn dry stack. Whew.

sunchaser said:

Recently became aware of the cost to replace antifreeze on a Nordhavn dry stack. Whew.

Click to expand...

What was the cost? Is it more involved than just removing all the old coolant from the keel cooler and engine? Must be...

cardude01 said:

What was the cost? Is it more involved than just removing all the old coolant from the keel cooler and engine? Must be...

Click to expand...

Depends on the design coolant volume, a few barrels to the landfill adds up too. Pick a model, find out the volume and add in labor.

My underlying point is it may not be cheaper over time. Potentially the reverse especially if one buys a used vessel that needs a new stack wrap job.

Nothing that a few boat bucks won't cover though.

I am cooling the Lugger with a Fernstrum keel cooler mounted just aft of the upward curvature of the hull, close to the full keel for grounding protection. This eliminated the heat exchanger mounted on the engine. 50/50 Antifreeze only, will be running in this loop. The s.s. exhaust elbow will be cooled with sea water from the engine driven raw water pump, and yes that means I have a thru- hull and strainer, but no saltwater touches the engine at all. My question is; I want to tap hot coolant from the loop to go to the raritan water heater with its built in exchanger. Where should I do this? Where should I take and where should I return? What diameter hose? Do I need bronze diverter fittings like in my house when I installed a heated towel warmer in the hydronic system?
Thanks guys.

I created manifolds just before the engine cooling lines enter and exit the cooler. Two manifolds are needed to maintain the supply and return circuits.

On my set up, I have four taps on each manifold with valves on each tap. I did this so I could easily add or remove a device without shutting down the engine or draining off coolant.

You could easily then add your water heater, transmission cooler, steering cooler, hydraulic system cooler, etc to the engine cooling circuit.

I would consider adding a gate valve in in the return circuit in case you have to throttle down the cooling pump.

With multiple devices now on the engine cooling circuit, you should install valves at the highest point, but below expansion tank, so you can get air out of the system. If the system gets an air lock, you'll be loving those bleed valves as they're fast and mess free way to deal with system.

Conall

What has not been mentioned and what I have found to be a weak spot in dry exhausts is /are expansion joints. That is usually where your dry exhaust leaks will tend to start and are often a pain to replace or repair.

I am new to kc/ds so not qualified, but will comment on my brief exposure during my recent survey and sea trial for the boat I just purchased in Holland. See pictures below.

My keel cooler is housed in these bilge keel housings that you see in the first picture. This is 6mm plate. It was warm to the touch when we hauled her after the sea trial and showing some steam in the 50 degree temps and high humidity. Add benefit may be a little stabilizing effect from these structures.
There are auxiliary circuits off the main circuit that cool the tranny and genny so even the genny is dry stacked and sits in a chase with the diesel heater exhaust. The chase for the main stack is just behind the pilot set and ahead of the settee on the upper level. In this cabin, there is no question that it was measurably quieter than my wet exhaust in Klee Wyck.
What was strange and almost unnerving to see when we pulled the boat to sound the hull was the complete absence of thru hulls. Total for this hull is one while Klee Wyck must have at least 10. Also strange to look at an engine room with no strainers (an engine room that 4 adults stood up in and discussed ship systems. Weird feeling for sure.
I guess I expect from this brief exposure that I will really like this system.
In terms of the external stack for the main, see second picture. There is a weighted flapper on the stack which you can make out just ahead of the TV dish low to the cabin roof. The weight is adjustable by screw and no need to cover or uncover the stack when in use or not.
The genny and diesel furnace stacks are right and left of the main stack protruding from the chase extensions from the main cabin.
NO evidence of soot anywhere from this 29 year old Mercedes V10 that is loaded to cruise hull speed (8.4) at 1400 RPM.

I spotted this one with dry stack this past weekend . We don't see much of this in our area . It has 6-71 Detroit and Westerbeke generator . Boat is keel cooled .

ulysses said:

What has not been mentioned and what I have found to be a weak spot in dry exhausts is /are expansion joints. That is usually where your dry exhaust leaks will tend to start and are often a pain to replace or repair.

Click to expand...

Would this be like a flexible stainless steel corrugated hose covered with sst braid and a coupling or flange on each
end ?

Pack Mule said:

Would this be like a flexible stainless steel corrugated hose covered with sst braid and a coupling or flange on each
end ?

Click to expand...

Yes, Corrugated SS or bellows like section with a flange on each end. No braid in my case. Then the whole thing was covered in a blanket.

Pack Mule: Yes that would be one of the good ones. Some look like an accordion with a flange on each end. It allows for thermal expansion between bulkheads, overheads and/or bracings (supports) so that the exhaust lines can expand when hot and not tear out the braces. Usually that is where you will get a leak either in the flex portion or the flange. Very messy job to replace and they never want to flange up correctly again. There is another style that is like a pipe with an inner pipe (flanged) and they allow expansion. I guess you would call it an expansion sleeve.