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Dry exhaust to wet exhaust

Discussion in 'Technical Discussion' started by Matt46post, Oct 28, 2017.

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  1. Matt46post

    Matt46post Senior Member

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    looking at changing a 60' boat from dry stack exhaust to wet exhaust thru the side of boat or under water exhaust, engines are 8V92 normally aspirated 350hp, large stand up walk around the engines size engine room , I believe parts should be easy to find ? And it should a fairly simple to find or fabricate pieces , am I missing something?, the boat is a flush deck trawler and I would like to remove the dry stack because it comes right thru the center of the salon/galley and has a 4'x4' surround around it for heat and fire protectection ,it justs awkward, and really feels like a huge elephant in the middle of the boat,plus they are messy at the marina with all the soot,I have seen other exact models of the boat with exhaust out the side so I know they were built both way at the factory, what do you think it will cost in parts and labor ?
  2. Capt J

    Capt J Senior Member

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    More than you want to spend!!! Probably $15k by the time you buy new exhaust, run the hoses, thru-hulls etc. etc.
  3. Capt Ralph

    Capt Ralph Senior Member

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    Dump cans alone will blow $15K each engine.
  4. captholli

    captholli Senior Member

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    I think J is pretty close with his estimate, I'm installing a wet horizontal muffler/resonator on top of the motors via brackets to save valuable space outboard that would be taken up by a vertical resonator. You can purchase Centek Vertical mufflers for $4,000 ea. for my application and the OP would be much less due to HP and cubic ft. area needed to regulate back pressure. The $$ comes into play with the custom stainless fabrication for spray rings, turbo collars & exhaust runs with hard lagging. This custom system going in is for 1,150 HP motors and was a tad over $25,000

    Attached Files:

  5. Matt46post

    Matt46post Senior Member

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    Thanks for the info guys, I figured it would be round $15-25k, I am looking at buying the boat, it’s a lot to spend but the amount of usable space and the increased ergonomics on the main deck and flybridge gained it make sense to me, by running the exhaust out the side of the amidship where the engines are am I going to get a lot more noise and fumes verses out the back ?The nice with current dry stack is the aft staterooms have more space because there is no exhaust running thru the boat
  6. Capt Ralph

    Capt Ralph Senior Member

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    You going to try below or at the water line thru hull?
    YF members have discussed under hull designs to keep gasses away from the wheels.
    Holes need fairing like a thruster tube also.

    Is she keel cooled or H/E?
    You may also need a (or larger) raw water pump, larger raw water thru hull and strainer.
  7. captholli

    captholli Senior Member

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    Keep in mind the cost of removing of your existing dry exhaust system and then the conversion of the dry exhaust casing for usable space on two decks. That 4' x 4' exhaust casing on the main deck, its bulk heads could be and more than likely are a structural component in the design of this vessel. Get a very good surveyor to perform due diligence and inform him of your plans to convert. Rule of thumb on refitting boats is that once you arrive at a $$ number for the removal of old systems , installation of new systems & conversion of old into usable space into new , take that $$ number and then double it for the contingency of the unknown that you'll certainly run into.
  8. Capt Ralph

    Capt Ralph Senior Member

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    Nice classy dance pole can help here. Send pics,,, of the dancers..
  9. Lepke

    Lepke Member

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    I ran PBRs in Vietnam with 2 6v53s. My group used a special quiet version, heavy engineroom insulation, their exhaust went out the stern and into rubber fittings that turned the exhaust 90° down. The fitting ended at the bottom of the hull, under water. At idle, along side a dock, you couldn't hear anything until you walked to the stern and heard the splash of the jets. At speed, quiet enough to sneak up on other boats at night.
    I've run many Detroit Diesels that exhausted out the side, and they are noisy at speed. Probably too noisy for a yacht without really good mufflers. And those were mostly 671s.
    I'd look at below the water options.
    My boat, 2 DDs, exhausts out the stern, below the swim ladder. Water lift mufflers and about a 30' run to the stern. I think it's quiet, but don't have perfect hearing.
  10. Matt46post

    Matt46post Senior Member

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    Thanks for all the input ,hopefully I can get these pics up the boat with the dry stack and a sistership with side exhaust ,if I remove the fiberglass structure that encloses dry stack, I will have to install joist to tie the ceiling together and sheet the bridge deck ,probably be a good idea to put a support pole in, I should be able to sell the dry stack parts? The fiber glass smoke stack on the bridge looks to be really heavy,, the exhaust would probably go out the side at the waterline behind the stabilizers 658BF796-02A4-4010-AB64-70F9E9D24CE9.jpeg 6AEF3645-190F-40A5-8694-978FFA76B446.jpeg EC8F8B4C-9B61-4336-A11C-3F20687F134F.jpeg EB81BD20-64F8-4870-BD27-F4B6C5C21EBF.jpeg A46066C1-7C4C-49BD-88C5-66588E21933E.jpeg
  11. Matt46post

    Matt46post Senior Member

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    This is the sister ship with side exhaust , I assume it’s at the waterline or the same level as it would if it was ran to the transom?it looks like there is a big muffler running on the starboard side below the port hole in the engine room, looks like the side exhaust is at the waterline in the picture C2A9ED36-C075-47A7-AFA2-C73C759CF7E9.jpeg B41B6EA9-C04C-4286-BE17-A507BBEAE59C.jpeg 321BFB2C-2F09-45D5-9800-C0E54B92F8AC.jpeg C2A9ED36-C075-47A7-AFA2-C73C759CF7E9.jpeg B33B9303-1802-408F-91E4-5891467002F8.jpeg B33B9303-1802-408F-91E4-5891467002F8.jpeg
  12. Matt46post

    Matt46post Senior Member

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    Does anybody have any experience with these 1980s vintage lien hwa trawler yachts? they all seem to be coming of the age and the fuel and water tanks area going bad and the teak decks are leaking and creating dry rot and water damage ,but it seems like the hulls are solid bullet proof fiberglass ....they don’t seem to be built nearly as well as a Hatteras, but if you can buy them really right they woukd make a nice liveabourd
  13. Matt46post

    Matt46post Senior Member

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    I don’t think there is room to put an under water muffler, I think it will have to out the side at the water line
  14. Matt46post

    Matt46post Senior Member

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    Thank you capt holli that’s good advice
    Rcrapps I think your on to something there, brass stripper pole ,turn on the red lights,and recruit in a few dancers and use there tip money to do the project , I wonder if the boat yard will have a problem getting paid in ones and lap dances?
  15. Capt Ralph

    Capt Ralph Senior Member

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    Now your on to something... but the yard folk will be lining up, the chandlers will be paid in 1s and entertainment.
  16. Capt Ralph

    Capt Ralph Senior Member

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    Room for an underwater muffler or thru hull?
    No muffler needed if the exhaust is going underwater.
    Big space saver. 8' glass tube from the hull bottom, maybe a 2' idle hole out the side at the water line.
    Single dump can from each engine.

    Mufflers seem to eat up some serious room in the second set of pics.
  17. Capt Ralph

    Capt Ralph Senior Member

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    Conventional H/E. Pretty simple there.
    Nice sized strainer and raw water lines.
    My early comments are not a concern after all. Your overboard water hose (H/E discharge) just re-connects to the dump can.
  18. Capt J

    Capt J Senior Member

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    You're going to have a lot of expense and what you'll gain is very dirty hull sides with the exhaust in that location, at slow speeds/trawler exhaust smell down the entire boat and even on the flybridge.

    I ran a 98' with the exhausts in that location that had MTU's 9v396's and under 8 knots the smell and smoke even on the flybridge was extremely annoying. For the little bit of space you'd gain, it's not worth the cost. I'm guessing the side exhaust boat is an earlier build than yours and they went to the dry exhaust on yours because they had to because of those reasons.
  19. captholli

    captholli Senior Member

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    MTU 9V-396 ? I missed that production run of motors. Was this a new model from MTU / 'Multiple Trouble Units"? Were they TB 92 or 94's?
  20. Capt Ralph

    Capt Ralph Senior Member

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    The USCG hates the side exhaust on their 80 & 90s. scrubbed weekly.

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