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  1. #1
    Join Date
    Aug 2010
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    NJ
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    Default Quieter exhaust?

    I have an '89 Saltare which has a 454 and straight pipes, too loud. I'd like to quiet it down. I first looked for SuperTrapps as they were factory on earlier boats but are NLA unless you can find NOS. Given that I see two options:

    One is the common fiberglass ski boat mufflers. None I've seen give a decibel reduction. Anything is better than nothing, but installing these would require cutting the floor and glassing in new wood so I'd rather not do that for an unknown change. I also see many threads mentioning these blowing out or cracking causing leaks, not great for anything at or below the water line.

    Another is transom mount mufflers, such as Hardin Marine offers (https://www.hardin-marine.com/p-1260...silencers.aspx). Theses claim 8-10 db reduction, or about half as loud. They're also compact and should be an easy install after getting the gas tank out of the way. I'm leaning towards trying these first and if still too loud I'll put the long ski boat mufflers in front of them.

    What options do you guys recommend or have tried to quiet down your boats?

  2. #2
    Join Date
    Aug 2010
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    NJ
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    Default

    I ordered the Hardin Marine transom mount silencers (https://www.cpperformance.com/p-1259...silencers.aspx). I was worried about the flange size and whether it will fit inside the recessed part of the hull. My exhaust tips are 3" and these require a 4" hole, so I'll have to drill out to 4". I was worried about the flange size fitting in the recess around the exhaust tips, but the flange it 6" OD which will fit with a little room to spare.

    After ordering I realized my risers have a 3.5" outlet, so it may have been more prudent to order 3.5" inlet transom mufflers and just get the 3.5" in/out ski boat mufflers as well tomaximize noise reduction while minimizing impact on performance. Realistically at marginally more power than the stock 330 HP I don't expect an appreciable difference in power. I've run 450 HP big blocks in cars through dual 2.5" exhaust, so 3" should be fine for a wet exhaust. The factory pyramid manifolds and risers are probably more of a restriction than dual 3" exhaust with mufflers. I'll see how these do and hopefully I don't have to tear up the floor and install the long ski boat mufflers.

  3. #3
    Join Date
    Apr 2002
    Location
    Austin
    Posts
    2,155

    Default

    Why no FAE type solution?

  4. #4
    Join Date
    Aug 2010
    Location
    NJ
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    1,375

    Default

    I have heard mixed reviews about the effect on the wake. I've not ruled out FAE, but it will be a last resort for me. The transom mufflers arrived today, so I should be able to get them installed this weekend.They seem like quality parts and have an internal flapper. I'll add a flapper on the end as well which should dampen noise somewhat from my experience with exhaust being noticeably louder when I had a flapper tear off. There is a .075" gap between the OD at each end of the muffler insert and the ID of the tip though. I may try to flare the inserts to fit more tightly in the tip and use a sealant on them. I'm cautiously optimistic, but suspect I'll be adding ski boat mufflers as well. I doubt that would be inadequate, but if so I'll try FAE at that point.

  5. #5
    Join Date
    Jul 2010
    Location
    N.W. Suburbs Chicago, IL
    Posts
    2,239

    Default

    Refresh my memory here Cadunkle, you primarily wakeboard behind your boat right? Are you talking about the resonating exhaust noise out the back or does it carry into the boat?
    '86 Comp TS6M - Reborn 2016
    Riding Connelly Skis

  6. #6
    Join Date
    Aug 2010
    Location
    NJ
    Posts
    1,375

    Default

    Yes, primary wakeboard and kneeboard. It's too loud both in the boat and behind it.

    I got the Hardin Marine tips installed today. The factory hole was 3.25", which I enlarged to 4" by using a 3.25" hole saw inside the 4" hole saw to serve as a guide. The existing hoses were the perfect length to get two clamps on each end. The original install has two clamps on the stainless straight pipe and one clamp on the tip. The original tips were plastic and had melted a fair amount. They also came right off with zero effort after loosening the clamp and removing the six screws. My bilge was dry for a couple years after replacing the rudder and resealing the platform brackets, but these must have started leaking.I don't feel so bad however this turns out as apparently it needed to be done anyway. I sealed the new tips with 4200 fast cure on the flange and smeared on the pipe and in the hole in the transom. Screws are #12 x 1" long, I reused the factory screws. The transom is about 1" thick toward the top of the exhaust hole and 1.25" towards the bottom.

    It won't be indicative of noise level in use, but I'll fire it up tomorrow in the driveway without the inserts and measure decibels at idle then install the inserts and measure again. If weather and other factors work out I'll take it out Sunday and get my subjective impression of noise reduction as well as measure decibels in the boat at idle and at speed.
    Attached Images Attached Images

  7. #7
    Join Date
    Aug 2010
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    NJ
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    Default

    And the installed picture...
    Attached Images Attached Images
    Last edited by cadunkle; 07-17-2020 at 09:24 PM.

  8. #8
    Join Date
    Aug 2010
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    NJ
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    Default

    Decibels as measured with a cheap Risepro $20 meter accurate to +-1.5 dB. I measured idling in my driveway standing 20' behind the boat and a few feet to the right, as well as at head level in the driver seat with pickup pointed to the rear. I measured a 5-6 dB decrease from both measuring positions. A 3 dB change is double or half the energy (or pressure) in the sound, though due to how the human ear hears sound a perceived doubling or half the loudness is closer to 10 dB. Considering this, even 5 dB is a significant reduction for my purposes.

    No baffles: 87 / 77
    Baffles: 81 / 72
    Baffles+flappers: 81 / 72

    Subjectively it is noticeably quieter and a lot of the harshness is taken out, but not as quiet as I had hoped for. The internal flappers are quite loud as they flap back and forth though I suspect that won't be noticeable in the water as they'll be under water at idle. I suspect with on the river at higher RPM, an unrestricted water supply, and more water flow they will muffle slightly better than on the hose. Judging from the design of the baffles the amount they will quiet it down is probably highly dependent on the amount of water flowing through them. Adding the external flappers didn't measurably change the loudness but subjectively changed the tone or harshness standing at various points around the boat. I'll leave them on as my experience years ago when one of the flappers tore off is that it was noticeable louder riding behind the boat.

    I'll update with a measurement from the drivers seat on the water. I won't have a straight pipe measurement but if there is interest I can pull the baffles at some point and compare. I suspect I'll be installing additional mufflers though, but I'll see how it does on the water first. If I want quieter Ultra Marine makes a ski boat muffler that should fit at 43" long and only 4.25" OD (https://www.myinboardmarine.com/coll...le-um-288-3001). They also make the same muffler with a 3.5" in and 3" out, I don't know that it would make any performance difference with the same internals output size but it might make the connection from the risers easier to have a longer hose and eliminate the reducers. I could always get a 3.5" muffler and relocate the reducers to the rear in case I ever wanted to swap for 3.5" in tips. Approximate measurement from front of straight pipe at the leading edge of the flange to the back of the back seat is 40". That could work out so the output flange of the muffler pipes through the bulkhead by about 2" or enough to fit two clamps for easy future servicing. Either way it's in the ballpark and I can make it fit if need be.

  9. #9
    Join Date
    Feb 2014
    Posts
    105

    Default

    I put a FAE on my 1995 comp that we only use for slalom. I can say it changed the wake, but I can't say it made it worse. At ski speeds it may have made it a little softer. Wakeboard speed looks unaffected.

  10. #10
    Join Date
    Aug 2010
    Location
    NJ
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    Thanks for the info on the wake with FAE, that makes me feel less concerned if I end up going that route.

    I spent the today on the water. It may be my imagination but I think there's a little less rumble and vibration at idle. This is plausible as the baffle could break up large bubbles into smaller bubbles. Noise at idle is of course not an issue with the exhaust under water.

    The first time accelerating there was a very noticeable decrease in exhaust volume. It's still loud, but also more mellow and not as harsh. The admiral immediately commented that it's much quieter. I'd imagine the noise will not carry as far or be as loud on shore or riding behind the boat, though I did not ride today. I don't have a measurement without baffles to compare to, but at 22 MPH I see 84-86 dB in the drivers seat. The same or slightly more up to nearly 3000 RPM. For comparison on the way to the ramp I take the highway. Towing at 65 MPH with windows down I see ~88 dB in my truck, and 91-92 dB from tire noise as cars pass.

    Above 3000 RPM it was over 90 dB and getting louder as I accelerated, unacceptable to me. I did not think to do a WOT pull and check noise at max RPM, or if the Hardin Marine tips affected top speed or RPM. I'd imagine not with my wee little PCM 454 with factory 330 HP and probably not over 350 HP with the minor improvements I've made.

    Being as in my typical use at 22 MPH and cruising under 30 MPH the noise is comparable or slightly less than driving my truck this is acceptable, but only barely. I'd imagine most folks would call it good enough. I'd like it quieter though. Given it's marginally acceptable I'm not going to cut the floor and install ski boat mufflers mid-season, but I may this winter. In the quest for a quieter exhaust I just ordered a pair of Gibson clamp on mufflers (https://gibsonperformance.com/i-2295...on-310001.html) to put on the tips behind the baffles. They don't show the internal construction or advertise a dB reduction, but they're short at 6.75" and might subdue the exhaust just enough. From the pictures it looks like a reverse louver that will splash some water around with the exhaust gas and make turbulence to muffle it. Worth a shot, hopefully they don't fall off. I'll measure dB in the driveway as well as on the water for comparison.

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