Quieter exhaust?

[cadunkle]

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.

[Mischief IV]

Love this thread. Great job on the specs.
However, my thought process works a little different than yours. The way I combatted the noise of the exhaust on my Sunsport 242 was to increase the decibel of the stereo system. Seriously.

At one point, I did think about FAE install but it has mixed reviews. Yes they work...when they stay attached to the boat. Referring mainly to aftermarket on older inboards.

Mufflers are cheap as I know several friends and family included that have had issues with them. My Sunsport 242, which has the ULTRA barrel style muffler, has now decided to implode. The baffles have come loose inside and it sounds like rocks in a washer machine. So, I'm going muffler delete using FAE straight pipes. I don't think it will make it any louder and I honestly love the sound of my inboards.

I'm at the lake...in an inboard...what's not to love about that sound?

[NoWake]

My muffler is mounted in the engine dog house. 91 comp. silent muffler. Think it may be the only existing one that hasn’t had the baffles burnt out of it. It is quieter than most but at 22Mph has a hum that could drive you crazy too, so may not be for you. Just a different sound. Super quiet at slalom speed though and at idle really don’t hear it running. Will try and find picks.

[cadunkle]

Good point about FAE staying attached. I was also concerned about drag and force on the mounting brackets as I've read a few people have had issues with parts coming loose. I also prefer to hear that my engine is running, but I'll take silent or bubbly if I can't get there with mufflers. That's disappointing about the Ultra Marine mufflers failing (particularly on a newer EFI boat less prone to backfire), I got the impression they were a little better than Centek. It may come down to inherent weakness in any fiberglass muffler and luck of the draw. I've not found a stainless, long, small diameter ski boat style muffler. I think having the multiple partially water filled chambers is necessary to get a significant volume reduction. I considered straight turndowns but think they may increase noise in the boat and the rubber flappers probably have a similar but less pronounced redirection. The silent rider style muffler on the back of the engine would be an option if I could find one with 3.5" in and 3" out, and certainly easier than pulling up the floor, but I'm only found 3" in/out. I won't have room to fit the reducers on there for a 3" in.

I'm a lifelong gearhead and love the sound of a healthy V8, but as I get older I'm realizing hearing damage adds up over the years. My goal with this project is primarily to preserve what's left of my hearing. I have a few vehicles and have taken steps to quiet them all down and now wear earplugs every time I ride a motorcycle even with quiet exhaust, for wind noise. Hearing loss sucks and can sneak up on you over time.

[2001Sunsport]

Do these FAE's actually fall off? Run the Comp at 34/35mph everyday, while skiing, and it hasn't budged in 2.5 years. Have had it over 40mph occasionally.

[cadunkle]

The Gibson muffler tips arrived today. I don't expect a significant volume reduction from the straight through with baffle design, but it's similar to a glasspack you'd use on a car but using water instead of fiberglass to muffle the sound. They are very short at about 6-5/8" overall with only 3-1/2" beyond where they slide into existing 4" tips. They slide about 3" over the existing tips, and the inner baffle goes up into the tips 3-5/8". This means they won't fit the Hardin Marine tips with baffles installed as there is only 2-7/16" from the center baffle to the end of the tip. The slot where the two bolts clamp onto the tips is also too narrow to slip past the bolt holding the baffle into the tips.

I will modify these to fit by widening the slot to about 1/2" to clear the bolt holding the baffles, and cut down the inside inner baffle to 2-1/4" or less, maybe 2". This will result in 3/16" to 7/16" of open 2.5" exhaust (ID of inner baffle) at the end of the Gibson tip, plus the area of the louvered baffles. Much of the exhaust gas will have to make a 180* turn and the rest will go through the louvers mixed with water. I suspect this will result in fairly significant volume reduction and a much more effective muffler than either Hardin Marine Baffle or Gibson tip alone.

This may be the hot ticket to get it where I'm comfortable, though it may be too restrictive on the top end. If it is too restrictive at high RPM I will remove the tips and trim more from the inner baffle until performance is acceptable. Given the low HP per cubic inch of the PCM 454 I don't expect any significant performance change.

[Hagman]

I've had my comp for over 35 years and tried many different ways over the years to quiet the rumble. The exhaust pipes are 3". So is a 2" glass pack. I got 2 -32" glass packs removed the guts. Took the baffle back to the muffler shop and had them flare the ends up to about 2 5/8 ". Raped the fiber glass back on the baffle and slid them into the 3" exhaust pipes. I know this is not Maurine and one would think that it would rust away but, 3 years so fare. The Ford sounds grate and I think it likes the little bit of extra back presser.