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  1. #1
    Seaman
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    Default Can a dry exhaust be routed through the prop exhaust route

    Can a dry exhaust be routed through the prop exhaust routeAnyone go from a wet to a dry exhaust and still channel exhaust through OEM route versus thru hull? I was looking for at engine dB info

    Anyone have a video or sound clip (from the engine compartment, NOT exhaust sound) of dry exhaust on a 5.7L with outdrive exhaust route.

    I know people said it was louder but how loud? I hear big engines with dry exhaust and engines with hull thru exhaust but how loud is it on factory engine with just dry exhaust and OEM exhaust route?

    Im looking for dB of in cabin noise, not asking about performance or open exhaust sounds......I guess im looking to save weight more than anything.

    Thank you

  2. #2
    Moderator achris's Avatar
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    Default Re: wet/dry exhaust opinions

    I doubt you can dry exhaust on a Mercruiser, too much rubber in the exhaust path...

    BTW, louder is not better.... Your fellow water users will thank you if you make it quieter...

    Chris......

  3. #3
    Seaman
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    Default Re: wet/dry exhaust opinions

    no looking for louder, thats why i want it to channel through the outdrive (underwater), im looking for better (path of least resistance) for the exhaust and im sure factory casting isnt the best flow for the exhaust.

    I want to know the sound difference from the engine compartment. I should have made that a little more clear in the original post.

  4. #4
    Rear Admiral Scott Danforth's Avatar
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    Default Re: wet/dry exhaust opinions

    the factory casting is the best for performance AND component longevity. As Chris mentioned. too much rubber in the path to not have a wet exhaust.

    what are your goals?
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  5. #5
    Moderator achris's Avatar
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    Default Re: wet/dry exhaust opinions

    Yeah, ok.. I've done some reading on dry vs wet... and it all says wet is the quieter. I know from both experience and anecdotal information that the performance difference between factory standard thru-prop and a clean out the back exhaust system (thru-hull if you like) is insignificant. I guess that's both ends of the spectrum you're looking at....

    Interestingly the thru-prop has the advantage of using the vacuum behind the propeller to help 'pull' the exhaust gases out of the drive.... So if there was an advantage to be gained, my money would be on thru-prop... I don't believe there's much to be gained by 'smoothing out' the exhaust path....

    Another interesting fact that may be considered... Lower resistance exhaust path may not be the path to more power. The correctly designed engine exhaust can increase power by increasing exhaust back-pressure just to the right amount... I had a friend once who had a Subaru engine in a VW combi van. He built the exhaust himself. 4" straight out the back. He complained that it used almost double the fuel of anyone else who had the same combination, without any power difference. I suggested he go back to a 2-1/4" exhaust, which he did. Same power, and his fuel consumption was back to being the same too...

    Chris......
    The world takes on a whole new perspective when viewed from 100' below...



    1972 Bertram 'Bahia Mar' 20
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  6. #6
    Seaman
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    Default Re: wet/dry exhaust opinions

    im going to rebuild my engine this year and as i have it out i want to explore as many options as possible. As i gather info it sounds like the weight from all the cast iron is somewhat a little unnecessary. If some can be saved from changing to aluminum (exhaust manifold, intake manifold, heads) im sure a couple hundred can be saved and overall better performance, not just focused on the HP part of performance. I see wet has it +/- but im just learning as why and why not. Sounds was the original reason for the post but is sounds like the heat would be a factor in some components also.

  7. #7
    Seaman
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    Default Re: wet/dry exhaust opinions

    Okay all makes sense, just didnt know if the same auto application applies to marine. I figured thru-prop would still apply back pressure. Power was a benefit but weight was also a factor. As cast aluminum wet exhaust manifolds are still $$$ i explored the option of dry manifold. I see dry hear and there but what are there reasons for certain application and if they could or shouldnt be applied to my idea.

    My plans are not to build a high HP engine ( i wish....damn Alpha One limits), but to build a fresh engine and alter some equipment to save weight and gain some other benefits, but the question wasnt for HP benefits as much as it was for weight saving purposes.

    Thank you all for the help understanding better about marine engine applications vs auto

  8. #8
    Moderator achris's Avatar
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    Default Re: wet/dry exhaust opinions

    If you want to explore the +/- of dry vs wet, just google search it... Plenty out there to read.

    If you operate in sea water, forget aluminium. Fresh water you'll get away with it...

    Without knowing the specifics of your boat we can't go anywhere with how much difference any weight saving will make. But even in a small boat (for a 5.7) a saving of 50% isn't going to gain you much. Better acceleration is about all. The best thing you can do for performance is work at the other end, propeller....

    Chris......

  9. #9
    Seaman
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    Default Re: wet/dry exhaust opinions

    google search didnt provide any in cabin sounds samples or talk about people who have info on it. Weight is minimal (understand) im looking to gain better plane at slow speeds, i already have new prop to try this spring. The goal to the search was for engine sound samples for dB differences between dry system using thru-prop route. I wasnt seeking or asking about performance or the sounds im seeking to achieve from a different exhaust option.

    I was simply looking to get opinions on how loud the exhaust (at the engine not at the outdrive/muffler/hull thru opening) would be in the boat from dry to wet exhaust.

    I was under the impression the wet exhaust was more for sound than cooling and if dry exhaust was ceramic coats or wrapped could solve the heat issue. I have learned heat maybe still an issue using the thru-prop route


    I changed post heading to better reflect what info i was seeking

  10. #10
    Moderator Bondo's Avatar
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    Default Re: wet/dry exhaust opinions

    Quote Originally Posted by dearmosd View Post
    google search didnt provide any in cabin sounds samples or talk about people who have info on it. Weight is minimal (understand) im looking to gain better plane at slow speeds, i already have new prop to try this spring. The goal to the search was for engine sound samples for dB differences between dry system using thru-prop route. I wasnt seeking or asking about performance or the sounds im seeking to achieve from a different exhaust option.

    I was simply looking to get opinions on how loud the exhaust (at the engine not at the outdrive/muffler/hull thru opening) would be in the boat from dry to wet exhaust.

    I was under the impression the wet exhaust was more for sound than cooling and if dry exhaust was ceramic coats or wrapped could solve the heat issue. I have learned heat maybe still an issue using the thru-prop route


    I changed post heading to better reflect what info i was seeking
    Ayuh,..... Unless you've got an open motorbox, ya can't run dry exhaust,...
    It's done like with over-transom jet-boat exhaust... Not Thru-hulls...
    'n even then, they run water injectors to cool the pipes abit, so's the chrome don't burn off...

    Wet exhaust is 'bout Coolin', not noise...

    With a full dry exhaust, the pipes will glow Red from heat, burnin' up yer boat...
    Any Grease is Better,..... Than No Grease at All.......

  11. #11
    Moderator achris's Avatar
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    It's actually a moot point. Even if you wanted to, you can't run a thru-prop exhaust dry.... The only way to reduce the exhaust noise in the engine bay it to add (more) sound proofing...

    Chris....
    The world takes on a whole new perspective when viewed from 100' below...



    1972 Bertram 'Bahia Mar' 20
    2006 Mercruiser 4.3MPI (0W617679) w/Alpha 1 Gen II (0W829301)
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  12. #12
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    i was thinking heat issues could be then explored with ceramic coating or header wrap or both, but as i keep asking it sounds like the wet exhaust is more for cooling purposes then noise. With heat issues more of a concern than noise and as i would like to keep thru-prop route (dont want open exhaust sound), my option is to look for cast aluminum wet exhaust which would solve the heat/noise but want to look further into weight differences.

  13. #13
    Moderator achris's Avatar
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    I have standard ceramic coated iron manifolds and elbows..When I'm running the main noise components are induction and mechanical, not exhaust.... Like I said, more sound proofing.....
    The world takes on a whole new perspective when viewed from 100' below...



    1972 Bertram 'Bahia Mar' 20
    2006 Mercruiser 4.3MPI (0W617679) w/Alpha 1 Gen II (0W829301)
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    Please don't send service questions in private messages. That's what the forum is for. Messages of thanks, always accepted.
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  14. #14
    Moderator Bondo's Avatar
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    Quote Originally Posted by dearmosd View Post
    i was thinking heat issues could be then explored with ceramic coating or header wrap or both, but as i keep asking it sounds like the wet exhaust is more for cooling purposes then noise. With heat issues more of a concern than noise and as i would like to keep thru-prop route (dont want open exhaust sound), my option is to look for cast aluminum wet exhaust which would solve the heat/noise but want to look further into weight differences.
    Ayuh,... Unless it's an open air exhaust, coatin's, 'n wraps ain't gonna do a thing, but give ya slightly more time, before the boat bursts into flames...
    Any Grease is Better,..... Than No Grease at All.......

  15. #15
    Seaman
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    so as i was getting al types of info from my thread i got a picture from a big engine setup.....now this is were i got my question, could a exhaust setup like this be connected to factory y-pipe then channel down to the prop. As i look at the pic i see a water plumbed to the exhaust, now i was under the impression that a wet set-up consisted of water flowing around the exhaust pipes, so it would the exhaust tubing inside a housing.

    Now with my question i thought of something like this as an exhaust manifold. Now i question how does the water not fall into the exhaust ports on the heads......pressure?

    So from the pic the water flows from the t-stat housing then to the bottom of the exhaust pipes and then pressure pushed the water/exhaust gases out through the rest of the setup (either thru-hull or possible thru-prop)

    As i thought i knew a little more than i thought as people post i keep learning so please help me learn or clear up my thoughts on how a marine system works.750carb02.jpg

    So i also question if this could hook up to a the y-pipe and go through the prop, would the temp still be to high that the rubber/plastic parts still be at risk?

  16. #16
    Moderator Bondo's Avatar
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    Ayuh,... Those are water-Jacketed headers,....

    See with they neck down right near the ends,...
    That's where the water is dumped into the exhaust flow....

    Yes, they'd probably work with a y-pipe, you'd just need the Right connector pipes...
    Any Grease is Better,..... Than No Grease at All.......

  17. #17
    Seaman
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    okay this is what i was thinking.

    650-13156.jpg

    now since (above pic) this is $2k i wanted to know what makes this worth $2k when you could get a pair of these (pic below)

    images.jpg

    Turn these upside down, add fittings to the bottom (flow water) and fabricate a riser fitting to connect from the manifold to stock y-pipe.

    like this
    Head4.jpg

    Sorry if this is a stupid idea. But what type of cabin noise would these produce over the OEM manifold

  18. #18
    Moderator Bondo's Avatar
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    Quote Originally Posted by dearmosd View Post
    okay this is what i was thinking.

    650-13156.jpg

    now since (above pic) this is $2k i wanted to know what makes this worth $2k when you could get a pair of these (pic below)

    images.jpg

    Turn these upside down, add fittings to the bottom (flow water) and fabricate a riser fitting to connect from the manifold to stock y-pipe.

    like this
    Head4.jpg

    Sorry if this is a stupid idea. But what type of cabin noise would these produce over the OEM manifold
    Ayuh,... The top picture, 'n the bottom picture are of Water-Jacketed Headers....

    The center picture is a single tube automotive block hugger headers...
    Puttin' water fittin's in 'em, 'n runnin' water into 'em, will Hydro-lock the motor....
    Any Grease is Better,..... Than No Grease at All.......

  19. #19
    Rear Admiral Howard Sterndrive's Avatar
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    Why do you want chrome? for the appearance?
    Unless you have a $25,000 racing motor, shininess and a few pounds are the only benefits to that stuff over stock cast iron manifolds.
    Stay with stock manifold, risers and voila:
    quiet, safe, legal and insurable and a whole bunch of gas money in your pocket.
    Baba-buoy.

  20. #20
    Senior Chief Petty Officer emilsr's Avatar
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    Good advice has been offered here. Stick to what works; don't try to reinvent the wheel. By the time you get the tails, brackets, etc, marine headers will cost around $2,000 PER SIDE. That's a bunch of money for something that will give you 1 or 2 mph if you're lucky.

  21. #21
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    I have a set of gil marine offshore manifolds and pipes. used and cheep. They are water jacked, dry exhaust. What are you trying to gain from wet stock exhaust?

    for what its worth there off a 30" spectre cat that had twin 454's would run 108mph. Thats why i ask what your trying to accomplish.

  22. #22
    Moderator Bondo's Avatar
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    Quote Originally Posted by MWG2600 View Post
    I have a set of gil marine offshore manifolds and pipes. used and cheep. They are water jacked, dry exhaust. What are you trying to gain from wet stock exhaust?

    for what its worth there off a 30" spectre cat that had twin 454's would run 108mph. Thats why i ask what your trying to accomplish.
    on a 5.7L
    Ayuh,.... BBC pipes don't fit a SBC...
    Any Grease is Better,..... Than No Grease at All.......

  23. #23
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    Very good point Bond-o, I assumed he had a bbc since he wants to go fast.

  24. #24
    Moderator Bondo's Avatar
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    Default Re: Can a dry exhaust be routed through the prop exhaust route

    Quote Originally Posted by MWG2600 View Post
    Very good point Bond-o, I assumed he had a bbc since he wants to go fast.
    Ayuh,.... I think/ thought the underlyin' goals are weight savin's, 'n noise reduction, in the boat's cabin....

    I think dearmosd is missin' the differences 'tween water jacketed, wet exhaust, 'n dry exhaust....
    Muchless, Where the exhaust is Dry, in water jacketed, 'n where it turns to Wet exhaust...

    We also still don't know Where he's floatin' 'is boat.... Saltwater, or Sweetwater,..??
    Any Grease is Better,..... Than No Grease at All.......

  25. #25

    Default Re: Can a dry exhaust be routed through the prop exhaust route

    Quote Originally Posted by dearmosd View Post
    But what type of cabin noise would these produce over the OEM manifold
    Yes, having an header exhaust system would sound much different than the stock Merc exhausts you have now if you were going for a performance type sound---headers will be louder in general but really not as quite as loud as you would expect on the inside if ran through stock formation unless you went with a completely "dry" system/set-up, which you cannot do safely or legally especially in an stock format within an closed environment.

    For additional information on headers, try googling "lightning headers marine".
    In the long run, Using OEM parts may just cost you less money!

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