Wet Exhaust vs Dry Exhaust 

Great video. I like the idea of going back to dry exhaust. Less complicated and frees up internal space in the engine room.

I think you need to research more on the " Detroit's are sensitive to back pressure" they are not scavenging thru ports in the cylinder, but have regular exhaust valves, just like a 4 stroke, if they were sensitive to back pressure you could NOT turbo charge them, and your video clearly shows that you CAN. I would get a muffler from a truck breakers yard. Keep up the great work.

Here in Maine, there is a law against commercial boats using wet exhaust. Seems some one thinks that the wet exhaust is more contaminating to the ocean. The local fishermen have found that having a dry exhaust is nicer as in during our fridgid winter months, the exhaust pipe is keeping the cabin and engine warm

Brilliant 2 vids this week. That clanking from the wet exhaust cover would have driven me completely insane

Just a note to Americans: US Coast Guard Regulations require WET (water jacketed) exhaust manifolds on all vessel inboard engine installations. There are insurance carrier implications as well.

This is Chad,all the way from Georgia, USA.just wanted to say hi and thank you for your videos. I really enjoy and appreciate you and sharing your experience with your boat. I hope to retire on one myself in a few years.take care.

Wow never thought I’d be interested in boats being a car mechanic/enthusiast but this is extremely interesting. I’ll keep watching for sure!

Well explained Stu, having NO prior knowledge of the two types of systems.....I like the dry exhaust version myself simply because it is simple and maintenance free with little risks associated with it. I can see the opposite with the wet exhaust, high maintenance and high risk due to pump failure or leakage...the space gained form removal of the wet exhaust is substantial too. Well done Stu keep up the good work mate 👍

There's more smoke than a cypress hill concert and that dude is just so calm about the situation, brilliant.

I think in the case of your boat that you are spot on going to a dry exhaust. Noise will be the only downside I can see. Bravo, on a great explanation on the merits of both.

That wet exhaust is like the duct work in my attic, right in the middle of everything and leaving no other useable space. Run your dry exhaust through an insulated box with air intakes at the top before going through the roof. Ditch the twin pipes for a good muffler and stack pipe. Simple is good. :)

Albert Einstein famously pointed out that "If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?"

Wet exhaust - farting in the bath. Dry exhaust - farting during the day. Oh, and great cleanup too! Cheers from New Zealand!

You did it again Stu, excellent video! You manage to more than just cover a subject as your exhaust, but for me you draw me into Dangar island. I hope to visit Australia someday, wish I could drive the bus there. This is great, I could listen to raconteur Rick all day with his colloquialisms. What it comes down to is a good person surrounded by other good people telling their stories along the way. Thanks again!

Love the cleanup of your workshop, well done! ;-)

I've NEVER Heard a Detroit So Quiet as yer Mate's was through that dry muffler! That's a damned GOOD Muffler, I'd call the guys who built it, they Know What They're Doing....If they can Silence the V-8 that well, your 4-71 will be No Challenge.Hate to see the Price Tag on that Stainless, though. Also, you want to recall that when your boat was built, nobody MADE a Muffler that WOULD Quiet a Detroit, which is no doubt why they Converted her to Wet. And you DEFINITELY Need the space. With the Wet piping Gone, you could also build a clamshell box around your motor, Soundproof the Hell out of it, and so keep it down to a dull rumble throughout the boat, Below Deck. BTW, you could also Shop for your flex-pipe and the New-Style Band-clamps at a Truck Parts store, instead of a Marine store, which should get you a BIG Price Discount. And the New-Style clamps seal MUCH better, and easier to install also. You just want to Run them a day or so, and Re-torque the bolts, after they get hot and Seat In. I can't Get OVER the Muffler on that boat! Even at the Helm it was just loud enough to hear the engine, so you could tell if it started running rough or missing..That was GREAT. I really LIKED you Shop Cleanup, BTW.

Wow, I'm basically an expert now on boat exhausts. Cool!

You have a real knack for explaining and educating....thank you.

Loved the cleanup. I Laughed out loud! Great Job cleaning Up Mate!

Great explanation of W vs D. Like your approach...go with D and KEEP with W until D is proven correct. Keep the great videos coming.

Man I LOVE your tidy-up methodology. As for the exhaust, it appears (to my un-educated mind) that the dry exhaust is clearly the way to go - particularly as the "infrastructure" is already there from the previous dry installation. Simplicity is the basis of a sound and reliable solution.

1 take out the wet exhaust and putting the dry exhaust back as it makes more sense and gives you more room.. I'm woching all ur videos to day from the start. Verry good videos Ray from England..give usr a shout out ples

i would go crazy listening to that metal flap banging on the back

Stu the island you live on looks ridiculously beautiful. Kudos man

Great job with the shop clean up. Love the flag on your mates boat.🏳️‍🌈

Your doing a great job man. One point about a dry exhaust. It's much simpler, therefor there is less to go wrong at the worst possible time. Like at night, where you can't see the shore, or any lights, and the weather is bad, and you need all the power your engine can give you. This is not the time, to have an exhaust issue. So, if I were you, I would go with, and keep the dry exhaust. Just one less thing to have to worry about.

That flap would drive me mad , Steve in Thailand.

Good vid Stu. One other option that a lot of commercial vessels use for a wet exhaust is to run the pipe externally and use it as a sponson. This is very popular in WA on cray boats.

Wow Steve your friend is out and proud of it.

Hi there :) Regarding the detroit diesel... there is no need to remove the turbo chargers. Remove the aftercooler/aircooler dismantle by taking off all its walls and clean it thoroughly with high pressure wash using something like degreaser or petrol to clear all the carbon soot which has collected within due to the exhaust manifold leak Stop the exhaust manifold leak and replace the air filters that will stop the smoke Since its a old detroit diesel the fuel pump on that engine does not have a boost compensator thus the fuel pump is injecting fuel at even though it is not getting enough boost IF there was a boost compensator with the same issue the engine would not smoke but you won't be able to reach max rpms In essence the engine is choking Hope this helps :)

I think you are doing great, being smart and asking questions and doing some research will pay off, running a dry exhaust before making a decision is smart, taking it apart with the possibility of reinstalling it if you had to might be wise also.

The effort to put this very informative video is appreciated and applauded. Learned a lot and look forward to all the many steps left in your project.

Dry just seems safer and more simple. When your out at sea, simple can mean the difference between life and death. Or at least a huge pain in the arse!

I know nothing about boats but loving this series your clean up was brilliant pissing my self can't wait for the next installment Thank you for the vids

Yes! A Mighty Car mods reference!!!

Well Stu, I'm not a marine mechanic but I do deal with diesel engines as a truck driver. My thought is dry exhaust is a better bet. My main reason is that wet involves salt water, steel, and heat and given the corrosive nature of salt alone it looks like a lot of potential trouble with corrosion. That and the dependency on the pump. Dry exhaust going straight up encased in a housing say 5" larger in diameter open at the top and bottom would draw air like a chimney around the exhaust pipe cooling it and providing some natural ventilation in the engine room. Seems like a lot less to go wrong. My thought is go high up with the muffler as your friend did. Should be available in stainless steel and I believe the engine manufacturer should have the spec for optimal back pressure rating for the muffler. Anyway, that's my thoughts on it. Love the videos, I always look forward to the next one! Cheers mate!

Like the old dude flying his pride flag.

Those Detroits sure are quiet. Ive worked around plenty on trucks, marine and industrial and love the sound. Good video by the way.

Wow, didn't expect a cleaning video from Dangar Stu.👌😄 7.08. My experience of 2-stroke engines is that exhausts are purely expansion chambers which do little muffling. I know there are equations to be worked out in making a petrol expansion chamber, not sure about diesel. Maybe this is why it was converted, because of the combination of 2-stroke and noise? I used to drive a Detroit diesel truck in the seventies and it WAS noisy even beside other trucks way back then, when everything was louder.

Followed you home from Brupeg. Some very important and interesting aspects to consider when restoring maritime real estate to safe and yet economical use and operation. Thanks, enjoyed it.

Good idea leaving the wet system in place until you are satisfied with the dry. There is less possible system failures with the dry. A proper muffler, sound deadening applications should do the trick. Will you be installing a gen set? Also with the stuffing box cooling the shaft nothing changes wet or dry. Looking good brother! I believe your wheel house will be quiet as compared to your friends boat as the engine is under the back deck instead of below the bridge.

I live in the Pacific Northwest of United States. And one of the biggest benefits I think of a dry exhaust with a stack is if you get any type of seasickness not breathing in the diesel fumes really helps.

Really good info here. Nice job ! I no longer have to explain to customers. Just gonna refer them here 👍

Canadian here. Don't sweat the messy stuff it's hard to do it all, all of the time. Life gets pretty busy and drawn out to do it all. There's only you doing this boat your doing a great job of it. It would be better if you could be with Brupeg or others to help. Keep on doing your best. God Bless you.

chop the lot out, use a flexi pipe up to deck head, then across to the side, and down to exit just above the water line , if need be you can use a rubber muffler outside to lesson noise and stop any backwash......... I have noticed with Stack Pipes if they are not high enough you get a back swirl of exhaust in the after deck when going forward, but a canopy could remedy it........... good luck with the project I have done a few of them mostly on wooden boats......cheers UK..

I had always read the speedboats and stuff have to do it for cooling, interesting to hear all the pros and cons stacked like this. Good stuff stu!

it might be the introvert in me but Im not worried about things being quiet enough to talk. facial expressions are all you need.

Nice explanation, very clear. I have worked on a trawler with a dry exhaust and it was noisey, but there was no muffler, or soundproofing fitted. A steel boat will always be noisier than a wooden one as the wood absorbs sound, while the steel echos and vibrates more.

Very informative Stu...thanks for the vid and great to see a couple of classic Detroit Diesels purring ...what a great sound. I'm thinking Brupeg has a dry stack ??

When I was a scout we had a 50 foot boat with a 671 diesel, it had wet exhaust with side discharge, that exhaust was great fun as it shot a fare size of water about fifteen to twenty feet while underway.

I had a dry exhaust until I had to have a mass removed from my colon...so more of a wet exhaust now. Can't say I have noticed a noise level difference at all.

I am currently re-fitting a steel trawler with a DD 4-71. She came with dry exhaust and I'm keeping her that way. Her engine is just below the cabin/helm and yes, 2 cycle Detroits are noisy. I've fitted a false flood in the cabin with 1" of rigid foam on top of a rubber mat over the steel decks, then plywood. Helps immensely. One clue is that you'be got to get a complete seal between the living space/engine compartment. Even a small opening will allow a lot of noise to pass. A huge thanks for researching the muffler! Mine's got one, but I suspect it's not the best configuration. Once you selected something I'll be following in your wake! I've also considered a removable pipe extension on top of the stack to move the actual exhaust port up higher and away from the aft deck. Thin wall stainless ducting ought to work. I'll report back if it works. Why all the off-topic comments on the flag? Seems like hyper-vigilance. The boat was a perfect example for the video, and I for one couldn't care a wit about what sort of flag anyone flies from their transom.

Hi mate...keep up the great work, your vids are awesome and cannot wait till the next instalment ....can't believe I'm getting excited about wet or dry exhausts 😂

Great hands on Explanation I can see you going back to dry Exhaust And like you said The key Is the muffler Can't wait to see what you come up with

I say dry, more space and maintenance possibilities is way higher priority than just noise. Noise should be secondary to maintenance. Also build your self a ladder for below deck. Obviously you’ll be doing down there often. Just a few steps should help a ton

Good job of showing the differences in the two systems. I think I might like the dry system better too. A lot of extra parts to make the wet system work and takes up a lot of space. Also, you're smart leaving the wet system in place until you're sure of what works best. And checking with the exhaust experts might convince you straight away to stay with the wet system once you find out what the dry system will cost you in performance and noise.

IF I ever have a wet/dry exhaust conundrum Now I know. 😁🤣Also Stu , you shouldn’t take sooo much time acquiescing to those who say CleanUp! Takes too much valuable time away from your excellent educational boating videos. 😜😁🤣🤣 Keep up the good work! 👍

Just for your info my father in law had a 52' Riviera with twin 400hp Detroits. Both motors were wet exhausts. When the boat was just cruising the motor noise was to the point, both inside and outside, very noisy. This was even though the engine bay under the rear floor was soundproofed. Also if you got a tailing wind the fumes coming from the twin rear wet exhausts was fairly powerful on the rear deck area causing us to have to go inside and close the rear door..unless the front hatch lids were opened but that was not possible in heavier seas. I have been on boats with stacked dry exhausts and they are quite different in that it does seem quieter and the fume problems were also a lot less depending on winds. Also access to both engines was extremely difficult, as you've pointed out, for maintenance on the Riviera because of the exhaust system. Just thought I'd put my two bobs worth on here. 😁🇦🇺👍🏻

Sick 2 vids in a week 👍👍

Another awesome video! My opinion after listening to what you said is that a dry exhaust is actually less complex than a wet system. I spent 9 years rebuilding an EH with a turbo motor and basically to compensate for backpressure issues from mufflers etc an increase in diameter might be needed. One thing to consider might be because the exhaust was so short on your boat may have made it quite loud. All of our generators at work use like an eggshell foam lining in the outer skin and it works extremely well that could be an option if it became an issue. Thanks again for an awesome vid!

Project Brupeg has a keel cooling system like you described.

Which ever you choose...Iam still very happy to watch your videos every week :-)

turbo detroits are a lot quieter than a naturally aspirated detroit so don't expect your 471na with wet exhaust to be as quiet as your mate's 8v71ta!

the shop clean up was Fantastic. Keep up the important work.

I laughed so hard when you "cleaned" up your workshop. When they are renovating a steel boat, they can comment.

Wet exhaust design: The exhaust pipe from the turbo or manifold should be water jacketed until it falls at least a foot towards the exhaust outlet. Sea water cooling from the heat exchange enters at the top of the jacket and exits through a water curtain into the exhaust pipe. The water curtain should allow a one or two PSI back pressure in the water jacket to maintain complete cooling. In my boat I have a low pressure water gauge installed in the sea water cooling system. It's the water jacket and cooling water which silences the exhaust. Gauges installed for my boat engine: coolant, oil pressure, turbo boost, tachometer, heat exchange sea water pressure and engine hour gauge. All these are necessary to monitor the engine performance and maintenance, running hours between oil change, etc. I hope this helps. Cheers Chris.

Having run quite a few boats with Detroit’s you can’t have enough sound insulation on a Them. No matter what you do make sure you have a considerable amount of insulation and a well designed muffler.

Great video Stu. You covered this topic really well and explained all the differences nicely.

It's interesting that the chickens appear more prominently in "a day in the life" video than Mrs. Dangar Marine.

I have no idea how I stumbled upon this video, but I learnt a lot of things!

can certainly see the huge benefit to dry in your situation. seems like a no brainier

Great video. Having been around car and industrial motors most of my life, don't assume a 4 cylinder industrial diesel will sound softer than a V8. It's totally how the exhaust is designed. Since the previous owner obviously switched to the wet system because he was loosing his hearing standing next to a dry exhaust system, really do your research-find a 471 in your area that has a dry system and check it out! Believe me, they'll be easy to spot.

I sure wish I was living in Australia. Thats so cool

Another thing to consider in the wet exhaust system, is that if the water is injected into the exhaust at or close to the water line, a siphon break is a good idea to install in the raw water discharge line with a loop above any possible water line. This ensures no water can siphon past the raw water pump and fill the exhaust. This is done primarily in sailboats and other vessels where the engine is below the waterline.

I would definitely go with dry exhaust.

Absolutely loved the ‘cleanup’ nearly fell out of my chair laughing, keep up the awesome work Stu!

Dry exhaust system seems to have advantages over the wet exhaust, below deck space and pump fail seem to be a disadvantage for the wet exhausts system. Nice upload today very interesting but a bit to short. I can watch your boat escapades for hours, looking forward to your next upload. Regards from a uk land lubber pom😊

I know I'm late to the party this series is awesome, Mad Max of the seas. Thank you

If I was in your shoes I would be yanking that old 4/71 and dropping in a 12 valve 5.9 Cummins the fuel savings alone would pay for the engine swap. Half the noise with a 12 valve, engine isn't flooding the bilge with oil, you don't have the Detroit diesel drone. Out on the West Coast of Canada we still work on gallons per hour with boats a 12 valve you'd be looking at .5 to 1 gallon per hour (2.2-4.5 litres) now with your 4/71 you'd be easily 3 gallons (13.5 litres) per hour. At our CND price per litre for diesel $1.40, a 12 hour watch on the boat 226 dollars with the Detroit, with the Cummins 75 dollars in fuel.

Years of Insulation wholesaling in south florida. Rigid DUCT BOARD for air conditioning . You will be very surprised. We soundproofed a lot of things like Pratt And Whitney jet engine test center. Sound studios and sold to a lot of yacht builders. Easy to work with. Best results.

Don't worry about the mess. "The space efficiency of pure chaos is hard to beat!" - Matthias Wandel

All sort of stupid conversions have been done to my boat by the second owner. The guy who build it know what he was doing. I would really like to convert it back to dry and go back to 24V instead of the 12V I have now. Hope you will go for the dry exhaust. 4-71's are sweet. I could listen to them all day with a good muffler. Wet exhaust is just like some one is puking at the back all the time :-)

Go with the dry it suite your stile of boat A kenworth muffler will fit that motor

I don’t like the idea of a dry exhaust but your space issues make it a really good idea

Wait a minute. You said the raw sea water is pumping water to only cool the exhaust. Isn't it going through the heat exchanger cooling the fresh water flow which is cooling the engine.

I've learned a lot about boating thanks to your videos and this was not an exception, keep up the good work. Cheers!

The Orka had a dry exhaust and it took out Jaws!!!

Keep up the good work mate. Possibly one of my new favorite youtube channels 👍

You Aussies like your beer. Not that that's a bad thing...!

All of my inboard wet exhaust systems had specialty cast wet jacket exhaust manifolds (big block Chevy) - quite literally ALL of the exhaust was cool to the touch. Vetus Marine makes very good marine exhaust components - the wet mufflers have integral dry lock anti water reversion designs.

go dry you won't be sorry. I have thrty years engineering fishing boats in Alaska. leave lots of air space in your stack!!!! heat rises. put a big blower to force air into engine room from out side. wrap all pipe well use as much sound deadener as you can afford

I so want to come hang with you guys. Tear it down build it back up and drink beer. Sounds like a solid plan to me . I have really enjoyed your videos since stumbling across them while looking for mustang restoration videos. Thanks for keeping it real.

Lose that flexi tube, the spiral contains Asbestos string. (Usual precautions) Go for a stainless bellows type instead. ( Did the former owner die of Asbestosis??)

Love your work Stu. Very interesting project you have going. Im learning heaps about bigger boats

Looking good with the flag waving behind you. Don’t really know much about boats but enjoy watching you fix em for sure.

I have owned and operated both wet and dry exhaust vessels. The dangers of a wet exhaust are: (A) going hard astern, where the sea washes back into the turbochargers, Particularly vulnerable craft are low slung speedboats. No room for a high-rise bend in the exhaust pipe before overboard skin fitting. (B) Heavy rain or leaky stern glands; especially low slung powerboats unattended at moorings or marina dock. These can cause entry of seawater into exhaust manifold and cylinders; wrecking the entire engine. As a boatyard proprietor I have had various customers with these problems. A dry exhaust with a large muffler (exhaust silencer) is the best, hands down. Raw cooling water appearing from skin fittings above the waterline then confirms that the heat exchanger is being supplied and no other possibility. As far as occupying space is concerned; no reason dictates funnel must be amidships. Awnings, Radar and antennae goalposts aft can carry exhaust pipes on either side.

I've owned several trawlers and sailboats all with wet exhaust. Even though you can cover a dry exhaust pipe it will still put out a lot of heat that will collect in the engine room. You will not be happy with that. Other systems will be affected by the heat. If you simply redesigned the wet exhaust to use space more efficiently you would have the best of both worlds.

I didn't realize this was converted from dry to wet and the infrastructure is there. Best guess is the noise drove him to a wet exhaust. Those 71's get loud even with the proper muffler. If you decide to go dry you could also think about a keel cooler and use the ports for the raw water suctions for the keel cooler. Heat exchangers require diligence monitoring the zincs and you need to inspect the unit itself once a year and possibly back flush it with some cleaner. Not that it's a problem for you, but it is a consideration. As far as the 71 maintenance goes...we had a whole list of things we did on an annual basis for exactly these engines. I'd recommend replacing the injectors, rebuilding both the water pumps, changing zincs, changing oil, fuel filters and racors. I have no idea how many hours it's been sitting or how many hours are on them now. Rebuilt injectors and pump rebuild kits aren't too expensive and are well worth the piece of mind. Also change the screen on the reduction gear. It wouldn't hurt to swap out the oil too. We used the same oil in the gear as our engines. You may not have that luxury. The hull repairs are looking solid. Can't wait to see the engine service vids. :)

I would be willing to bet that heat was the reason for converting to a wet exhaust system. The engine may well have keen running too hot.

Hello Stu, I've been pondering the muffler question for your engine. There is a guy in the USA who is an absolute Detroit Diesel guru. He posts on RU-vid as Bus Grease Monkey, he is a mechanic who travels thousands of miles a year in his fully equipped vintage bus to work on peoples Detroit Diesel equipped buses. Thus far I've not seen a single aspect of these awesome engines that he isn't able to tackle. I'm sure that if you contacted him with your questions and thoughts he'd be happy and very able to help you out. He's a thoroughly nice guy and a mine of knowledge. Regards from the UK.