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Quite exhaust??

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Section - I have been thinking........Yeah I know that is dangerous....My boat has twin 454 Chevys, actually ...
   
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  1. #1
    Lt Commander
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    Default Quite exhaust??

    I have been thinking........Yeah I know that is dangerous....My boat has twin 454 Chevys, actually they are 498's now...(I can't leave anything alone ) with 5 in. thru hull exhaust. It has mufflers, but it is still LOUD at cruising speed. I was looking around on the net the other day and found a exhaust called Fresh Air Exhaust systems has anyone ever heard of it? The systems are made for any boat with thru hull exhaust it directs the exhaust down into the prop wash and claims to cut the noise by 50 to 75 %. I ran Alcohol Funnycars in NHRA and my ears still ring. I'm just wanting to be quite for a change, it sounds good but I want to relax and not yell cruising down the river. Any body have any thoughts on how to quite things down? Thanks Guys Jamie

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    I haven't heard anything about them, but I know what you mean about the exhaust. Mine are quite loud as well since they are out of the water when the boat steps up on plane.
    ~ on the hook ~

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    I have seen boats use underwater type exhaust or extensions before. It may be your only option short of a different muffler inside the boat.

    It has me thinking, although we all hate the thought of more underwater holes in our boats, what about an exhaust out the bottom if the hull? Too much back pressure? Too quiet? Too easy to not spot potential issues (smoke/fuel etc)?
    '84 Silverton 34' T/270s.

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    I have wondered the same thing Mustang, if not through the bottom pipe it out above waterline and discharge it below the surface, especially on a genset. I would think that could help with CO issues while you are on the hook. I know there would be some back pressure but how much is too much. I wonder if a manufacturer would provide us with an answer?
    ~ on the hook ~

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    This won't affect Jamie's big blocks but boats with diesels that turn their exhaust down into the water find that they have more black soot from the diesel fumes mixing with the water than they would if they had run them above the waterline.

    Maybe because I'm 34y/o but two 454 big blocks at cruise would be the best sound in the world lol :-D

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    Quote Originally Posted by 25thmustang View Post
    I have seen boats use underwater type exhaust or extensions before. It may be your only option short of a different muffler inside the boat.

    It has me thinking, although we all hate the thought of more underwater holes in our boats, what about an exhaust out the bottom if the hull? Too much back pressure? Too quiet? Too easy to not spot potential issues (smoke/fuel etc)?
    I'm thinking back pressure would be an issue. Especially for slow tugs like mine lol. Go up I reckon! Stick some big ol Mack truck smoke stacks on em and let it rip lol :-D

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    Seems to me like a lot of the "Be Loud-Go Fast" boats around here have the exhaust just below the waterline at 'displacement speed' which results in a rather burbley (best I could come up with) sounding exhaust. I would imagine there's a LOT of back pressure created by a below-the-waterline discharge though, as well as greater risk of drawing water back into the engine under the right (or wrong) circumstances. There are some very effective mufflers out there though, my neighbors Trojan has a pair of 440s (big blocks) with side discharges (inboards- rear discharge would have to go through the stateroom lol) and even at planing speed she's still pretty quiet. Our small blocks rumble pretty good through the smallish mufflers we have, but it's not difficult to carry on a conversation at cruise- even in the cockpit.

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    Lt Commander
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    My exhaust is half out out of the water even at the dock. The Fresh Air Exhaust mounts to the thru hull outlets and takes the exhaust down into the water. It doesn't require any holes to be drilled its all behind the boat. It has mufflers now they are about 30 inches by 10 Inches. But they are straight thru. What kind or mufflers do you have?

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    Lt Commander
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    Hey Matt, picture this four 5inch chrome stacks about 8 ft tall cut on 45 degree angles mounted onto the transom....on the outside of the boat of course so no one would get burned sitting in the rear seats lol. I think were onto something here

  10. #10
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    Quote Originally Posted by jamie 10017 View Post
    Hey Matt, picture this four 5inch chrome stacks about 8 ft tall cut on 45 degree angles mounted onto the transom....on the outside of the boat of course so no one would get burned sitting in the rear seats lol. I think were onto something here
    Stop it. I'm starting to get aroused! Haha :-D

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