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I/O Exhaust Noise... Any Ideas?

LakeOconeeGuy

LakeOconeeGuy

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Well I traded in my 2008 RCW2575 I/O for a 2012 RCW2575 I/O and decided to upgrade to the 5.7L Mercruiser with the dual prop. The power is awesome but compared to my older 5.0L Mercrusier it's noticeably louder when cruising at slow speeds. Under acceleration / high speed there's no real difference in the onboard noise level and clearly the 5.7L will get up and go when it's time to pull a tube or wakeboarder but we spend a lot of time cruising around the lake at slow speeds enjoying a glass of wine.

Not sure if I like the rumble of the 5.7L Mercruiser on those relaxing wine cruises and I know it's annoying to my wife. When I asked my dealer I was told that my old 5.0L had the exhaust vented through the prop and the 5.7L has the exhaust vented through rear of the boat under the swim platform. That didn't make a lot of sense to me, but might be why the engine rumble is so much more noticeable...

Anyone out there from TEAM BENNINGTON or any other Benny I/O owners have any ideas about how to muffle / reduce the exhaust noise of this beast at slow speeds?
 
I honestly don't know off the top of my head whether there is anything you can get directly from Bennington or your marina, since I am uncertain which exact system you HAVE nor what you COULD have.

Having said that, what you essentially have there is a Third Generation (Gen III) Small Block Chevy and you can find all sorts of goodies at either Jegs or Summit. Don't just look in the street car section. There has been a lot of muffler development for race cars over the last 20 years as dragstrips and oval tracks have had to contend with noise regulations. Just do yourself a favor and look at the Stainless choices.
 
UPDATE! I noticed the engine noise on the test run I made with the dealer this morning and was really fretting over it... (Which lead to my post a few hours ago) My new Benny is scheduled to be delivered in the morning and I really thought this added exhaust noise was something I was going to just have to learn to deal with! But I just got a call from Bill Crowe at Crowe Marine (my dealer here at Lake Oconee) and his service department came up with a solution! Apparently the design of the Bravo III 5.7L Mercruiser was the root of the problem and they were able to add some type of accordion exhaust from the Bravo I engine and vent the exhaust out under water. He's says it's much quieter now! If you're ever in need of a Bennington at Lake Oconne - CROWE MARINE is the place to go!
 
Fiberglass marine mufflers are certainly available, and you can read about them @ http://www.overtons.com/modperl/product/catalog.cgi?cname=Mufflers-Soundproofing&r=browse s_kwcid=adwords_marine_mufflers

The good sounding V-8 boats are exhausted underwater with a flap style cover to keep water out. Exhaust work needs to be done properly, and a corrugated exhaust pipe is just not enough. It also needs a muffler to do the job right. They need muffled at an idle and when the boat is up to speed.

We have some Donzi big block V-8 boats down the lake without any mufflers, and they're a nuisance to the lake residents when they come by.

I have a friend down the road with a late '70's 23' Correct Craft straight inboard. His boat has a real classy sound at all speeds.
 
My 2012 8.2 I/O Q vents the exhaust thru the props. I wonder if the boat you test drove had the above water exhausts or captains call exhaust added. Most 350 mags I have seen or had exhausted thru the props unless the Captains call exhaust option was added. I don't know much about cat engines they might have a different exhaust system. My 8.2 is a cat engine and exhausts thru the props. I am not aware of a captains call option that Bennington offers from the factory my dealer checked when I ordered my Bennington. I would have ordered it if it was available. Thought about adding it, but my wife hardly lets me use it on our Chaparral, says its to loud and gives her a headache.
 
Bravo 3's do not have the exhaust bellows because the larger engine ( 8.1) would blow them out but if yer runnin a 350 you can just add the exhaust bellow.

Cheers

Ken
 
Ken H said:
Bravo 3's do not have the exhaust bellows because the larger engine ( 8.1) would blow them out but if yer runnin a 350 you can just add the exhaust bellow.

Cheers

Ken
Click to expand...
Thanks for all the input and advice. I'm pretty sure what the dealer did to solve the issue was add the exhaust bellow suggested by Ken H (Because I do have the 350), but whatever the dealer did - the PROBLEM IS SOLVED!!!
 
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