Wet vs dry exhaust

After 20 years now , done about '94, and about 3-4,000hr my bellows/accordion pieces seem to be doing fine still.
As for the flanges, on each bellows is a solid flange and on the other end is a rotating flange so line up is not a problem. Just need to use a good gasket. Support is also important so the bellows is not carrying the weight from the rest of the system.

This setup has outlasted the original exhaust setup which had a slider sleeve . Can't say, of course, that tomorrow I won't discover I have a problem.

C lectric:

Yours sounds like a good one too. The ones I have had to repair did not have a swivel on the flange and for some reason two of them did not have the fixed flanges parallel which meant while bolting them together you put a bind on one side of the accordion part. Thus those did not last too long. The expansion joint NOT carrying the weight as you so correctly put it was probably the reason those did not last too long.

The "slider sleeve" ones I never had the opportunity to dismantle but I always assumed there was some form of packing involved.

One note on the Delfin's dry stack. The Ulysses is a sister and evidently had a dry stack at one time. The exhaust race is still evident, I imagine there was a story there at one time.

I used to work for a rubber and gasket company. We made them in all kinds of configurations . I never thought about them being used for exhaust on boat , but I wasn't into boats back then . We would cut the bellows and the braid to length then put it all together and weld the braid to a ring and then weld that to the bellows then weld whatever coupling or flange to that . We also made them with bronze bellows and braid .

I dunno, I kinda like the sound of my twin Perkins 4-236s with wet exhaust. Kinda mellow burble.

Kevin

An expensive Hospital Grade exhaust will be as loud as a Lincoln underway.

One time expense , then silence!

Conall, thanks for replying about the manifolds. Could I bother you to send me some pictures of your set up? I also want this loop to feed a red dot bus heater to defrost my pilot house windows so it's getting complicated in my mind. Lol
My email is sjemery at gmail dot com.

FF A "hospital grade exhaust will be as loud as a Lincoln underway" might be an understatement. Maybe one of those Chevy Volts might be more appropriate analogy. If I remember correctly it will reduce noise attenuation down to about 40dBA.

The drawbacks of course are weight and size. The dia. will be about 4X the pipe size and the weight can be substantial. If you have the room that would be the way to go if you want quiet. These days I do not even know if I can hear 40 dBA anymore. Too many years listening to a 5800 HP boat's engine.

I always figured that the higher RPMs and higher exhaust flow when SF back down keep out water.

Steve,

I'll get some pictures in the next day or so and send them your way.

Conall

Thank you very much, it is greatly appreciated. Love your boat.
Steve

"I also want this loop to feed a red dot bus heater to defrost my pilot house windows so it's getting complicated in my mind."

Not so,, most engines will have a few areas where hot water can be tapped and returned.

Worst would be a small centrifugal pump might be needed.

Do not series HW heater and box heaters , single valved circuits.

Worst case simply tap off of engine coolant before bypass thermostat to keel cooler , return it just before cooler return to thermostat.

All I have to worry about is that the heat exchanger in the water heater, as well as a manifold and hoses that will feed it, should all be lower than the cap on my expansion tank...is that correct?

Do all these dry exhausts use wet exhaust manifolds with coolant?

Or are the exhaust manifolds wrapped with insulation?

How exactly are the systems configured?

I'm trying to educate myself as well . I just googled images on keel cool dry exhaust .it helped me get a better idea .

Yes, dry exhaust piping is insulated usually with a blanket wrap. Basically a "wet exhaust" allows for a raw water engine driven pump to supply water from outside the boat then through a heat exchange that cools the coolant in the engine which also circulates. The raw water then mixes with the exhaust and goes out with the exhaust. In a dry exhaust system just like your car the exhaust goes through a silencer (muffler) then out usually through a high stack. The exhaust is not cooled as that is not necessary. The engine is cooled by circulating the coolant through a pipe external to the boat in a closed loop type arrangement. If you can imagine, your radiator in your car uses a closed system too that circulates the engine coolant through the radiator. The radiator uses air flow to cool the water in the case of the boat system the external pipe (keel cooler) operates by cooling the engine water by means of the ambient water temperature surrounding the boat rather than air.
As mentioned above, both systems have their advantages and disadvantages.

sdowney717 said:

Do all these dry exhausts use wet exhaust manifolds with coolant?

Or are the exhaust manifolds wrapped with insulation?

How exactly are the systems configured?

Click to expand...

Some use manifolds with cooling jackets, some the manifolds are not cooled, but insulated. Most purpose built marine engines, even if intended for keel cooling will use a cooled manifold. Mostly to limit fire risk and to keep engine room temps down.

Many keel cooled engines are sourced from industrial or road engines, and those usually have "dry" manifolds.

In the case of keel cooling with dry stack, the engine does not "know" it is in a boat. It has no interface with sea water like a normal "wet" engine. So an industrial engine can simply be dropped in and hooked up with minimal changes, including exh manifold.

On a largely non variable waterline recreational vessel why is a dry stack used? To have fun, be different and appear working trawler like are the credible answers I've heard. No doubt they work just fine if one is accepting of the downsides. And your boat and neighbors don't mind soot.

sunchaser said:

On a largely non variable waterline recreational vessel why is a dry stack used? To have fun, be different and appear working trawler like are the credible answers I've heard. No doubt they work just fine if one is accepting of the downsides. And your boat and neighbors don't mind soot.

Click to expand...

It seems about half the problems on marine engines come from sea water pumps, wet exhaust reversion and corrosion, sea water leaks on coolers, and things corroding where sea water contacts engine stuff.

Keel cool with dry stack has none of these issues.

Downside is noise, soot, heat issues and corrosion issues in the dry pipe/muffler rig. Dry also probably more expensive and eats up interior space.

I think they type of boat where dry is best is pretty rare. And that's what we see in the fleet. Mostly wet.

I do like the "coolness" factor of dry, though.

Ski in NC said:

Some use manifolds with cooling jackets, some the manifolds are not cooled, but insulated. Most purpose built marine engines, even if intended for keel cooling will use a cooled manifold. Mostly to limit fire risk and to keep engine room temps down.

Many keel cooled engines are sourced from industrial or road engines, and those usually have "dry" manifolds.

In the case of keel cooling with dry stack, the engine does not "know" it is in a boat. It has no interface with sea water like a normal "wet" engine. So an industrial engine can simply be dropped in and hooked up with minimal changes, including exh manifold.

Click to expand...

How well would a simple wrapping of the exhaust manifold work and how thick would must it be for a decent reduction in heat if you used this, versus some kind of blanket this company also sells.
https://www.heatshieldproducts.com/marine/marine-exhaust-insulation/premium-marine-exhaust-wrap

Or is this not the appropriate usage for a manifold?



Advertises a tighter weave versus their normal weave product, any thoughts?

This other one has higher rating, think it could fit on an exhaust log type manifold?
As in cut around the port connectors to the head.
https://www.heatshieldproducts.com/marine-exhaust-insulation

The inner ceramic liner makes it capable of withstanding 1800°F continuous, which allows this heat shield to be placed directly on turbo manifolds, down pipes, and exhaust pipes.

Click to expand...

sdowney717 said:

How well would a simple wrapping of the exhaust manifold work and how thick would must it be for a decent reduction in heat if you used this, versus some kind of blanket this company also sells.
https://www.heatshieldproducts.com/marine/marine-exhaust-insulation/premium-marine-exhaust-wrap

Or is this not the appropriate usage for a manifold?

Advertises a tighter weave versus their normal weave product, any thoughts?

Click to expand...

Depends on the manifold shape. Some are very hard to wrap, some easy. Fabricated sheet metal shaped to fit is another way, blocks the radiative heat transfer. Look at how the QSM11 dry manifold/turbo is insulated.

Ski in NC said:

It seems about half the problems on marine engines come from sea water pumps, wet exhaust reversion and corrosion, sea water leaks on coolers, and things corroding where sea water contacts engine stuff.
.

Click to expand...

Ski

Two things. First, a trip into a Nordhavn ER with dry stack (not all are) finds several places where sea water is used for cooling. Not to mention very large exhaust fans to keep ER cool.

Second, you built your own boat. Why not dry stack?

sunchaser said:

Ski

Two things. First, a trip into a Nordhavn ER with dry stack (not all are) finds several places where sea water is used for cooling. Not to mention very large exhaust fans to keep ER cool.

Second, you built your own boat. Why not dry stack?

Click to expand...

For the reasons you edited out of my quoted post.

Ski in NC said:

Depends on the manifold shape. Some are very hard to wrap, some easy. Fabricated sheet metal shaped to fit is another way, blocks the radiative heat transfer. Look at how the QSM11 dry manifold/turbo is insulated.

Click to expand...

I have sort of been interested in the International 466.
Here is an exhaust manifold for it.
Thoughts about if it was wrapped, it seems fairly simple?

That one should be pretty easy to wrap. Then get a blanket made for the turbo scroll, those are truly hard to wrap due to the shape.

Wet exhaust Intl 466 manifolds can be had from Mesa Marine , but the cost more than one would pay for the engine.

These can be plumbed to the keel cooler with the engine circ water.

A wrap is as good at keeping the engine room temps down ,the thick pro built the best!

stevensibs said:

Conall, thanks for replying about the manifolds. Could I bother you to send me some pictures of your set up? I also want this loop to feed a red dot bus heater to defrost my pilot house windows so it's getting complicated in my mind. Lol
My email is sjemery at gmail dot com.

Click to expand...

Hi Conall

I am also interested in seeing your system in pictures, and would
certainly appreciate an email from you. Currently developing an
entirely new heating/cooling system for my boat.

Thank you kindly
Capt Nemo
northchannel@msn.com

I sent you some pics Nemo.

My engine is a Deere marine engine with a coolant header tank and no external exhaust manifold as one would find on a non marine industrial engine. The engine is turbo charged.

I wrapped the exhaust with two inch thick ceramic insulation and wrapped the ceramic insulation in a fiberglass welding blanket to contain the ceramic. It looks pretty home made, but works well as you can wrap your arms around the exhaust when the engine is running. The turbo is wrapped with a custom blanket. The exhaust silencer whic in the engine room, is also wrapped, and is of the dump truck variety. All the exhaust piping in the stack itself is not wrapped and is cooled by air being forced up the funnel.

I did not wrap the exhaust pipe in the funnel on purpose as to get some heat out of the pipe so it does not damage paint as it exits the funnel on top of the boat. The funnel is obviously steel, and with it being insulated, it deals with radiant heat well. This aspect of my design seems to be working well as no paint is getting damaged and the exhaust pipe is relatively cool by the time it exits the funnel. The key here is the amount of cooling air flooding up the exhaust side of the stack from the funnel being partitioned and the ER being pressurized. The ER door has to be closed.

My exhaust funnel is about 2' x 2', and has a partition in the center of it. One side of the partition is intake air, and the other side if for the exhaust pipe and engine room hot air exhaust. The exhaust side of the funnel has high performance heat shielding lining the walls. I created a partition in the funnel as to not allow intake or exhaust air to short circuit and mix.

The ER is pretty air tight, and when the door is closed, I consider it pressurized. Intake air is provided by a quality axial fan I purchased from Delta T, and so far, that fan has done an amazing job. I do keep a spare fan on board.

I have a thermometer in the ER to keep an eye on the temperature, and do monitor it closely. On an 85 degree day after running the engine around 1600-1700 I'll see ER temps around 111 degrees Fahrenheit after about 6 hours of running. It seems to take the better part of the day for temperatures to climb over 110. The highest temperature I've seen was 115, and that was after an extended run at 2200 RPM while dealing with current on the Cumberland River. The ER temps seems to get to 103 fairly quickly, and then start a slow climb to top out at, like I said, around 111.

The engine is a Deere 6068TFM. I specified the engine to have 190 degree thermostats in it as I feel diesels need to be run on the warm side. Any temperatures under 205 but above 180 is fine with me. I'm happy with the ER temps I'm seeing given the mass of the main engine and generator, but I'd be interested in what kind of ER temps others see with similar set ups.

Conall

Not the best pic , but how does this look ?

Greetings,
Mr. PM. Looks better than a LOT I've seen.

I'm out on wrapping an exhaust manifold and turbo, if there is any other alternative. Personally, I would select an engine that has available, at a decent price, and not custom built, jacket water cooled exhaust manifold and turbo. (Cummins ?) Why would anyone do otherwise, I dont get it. Its safer, and why would you want to save a few bucks in that area anyway. Almost everything else costs more $$$ than the exhaust. Dont get me wrong, I do like dry exhaust, just not dry manifold/turbos. I know, some will say "just as good" but to me that means almost as good or not as good, depending on who did it and how. That 6/71 in the pic has a jacket water cooled manifold.