Exhaust Silencer/muffler/baffle ideas

[BigBoatinOkie]

Howdy. I have a Merc 228/Chevy 305 I/O with 3" thru hull exhaust. The boat sounds mean with the straight exhaust, particularly when idling through the marina, but frankly I'm getting sick of the noise. We mostly use the boat for skiing/tubing/kneeboarding, and having that un-muffled exhaust pointing straight out the back gets annoying after a while. I've looked a lot online for some sort of muffler and found a few options. There are a few choices of slip in silencers that just go inside the tips or inside the hose and are fairly cheap, but they are all for 4" exhaust. There are several inline mufflers that can be clamped on between the risers and tips, but they all cost $300+. Then there are the tips with built in silencers, and they are also $300+. The slip-ins are perfect and cheap if I could just find some in 3" diameter.

1. Does anyone know of a slip in silencer for 3" exhaust for sale?
2. Does anyone know of an inline muffler/silencer/baffle that is affordable?
3. Anyone have an idea for building my own muffler of some type or know any tricks for reducing the noise?

I don't really need it to be quiet, but I'd just like to tone it down a few decibels. I suppose turning the tips downward would help some, but tips aren't cheap at all.

 

[Bondo]

Re: Exhaust Silencer/muffler/baffle ideas

Howdy. I have a Merc 228/Chevy 305 I/O with 3" thru hull exhaust. The boat sounds mean with the straight exhaust, particularly when idling through the marina, but frankly I'm getting sick of the noise. We mostly use the boat for skiing/tubing/kneeboarding, and having that un-muffled exhaust pointing straight out the back gets annoying after a while. I've looked a lot online for some sort of muffler and found a few options. There are a few choices of slip in silencers that just go inside the tips or inside the hose and are fairly cheap, but they are all for 4" exhaust. There are several inline mufflers that can be clamped on between the risers and tips, but they all cost $300+. Then there are the tips with built in silencers, and they are also $300+. The slip-ins are perfect and cheap if I could just find some in 3" diameter.

1. Does anyone know of a slip in silencer for 3" exhaust for sale?
2. Does anyone know of an inline muffler/silencer/baffle that is affordable?
3. Anyone have an idea for building my own muffler of some type or know any tricks for reducing the noise?

I don't really need it to be quiet, but I'd just like to tone it down a few decibels. I suppose turning the tips downward would help some, but tips aren't cheap at all.

Ayuh,.... I put thru-hulls on my barge 'bout 12/ 14 years ago, when I pulled the 3.0l, 'n dropped in a 4.3l...

I've tried MANY different things to quite it down...
If, 'n when the motor comes back out, a Y-pipe is goin' back in...

All the things you mention, do quite it,... Slightly....

The only way it'll become Quite, is to dump the pipes Underwater...

At this point, I have huge pipes comin' out, 'n tippin' down with 45?s which exit, a couple inches below the water, at idle...
Drop the Hammer, 'n when it breaks onto plane,.... She's Bellerin' to beat 'ell again....

Here in NYS, it's Legal, as they measure at the dock, at 10' away...

So, to answer yer questions,...
No,... I doubt you'll be happy with the noise, with any of yer posted options...

 

[oldjeep]

Re: Exhaust Silencer/muffler/baffle ideas

You might see if they make a version of this system for an I/O
http://www.freshairexhaust.com/

 

[BigBoatinOkie]

Re: Exhaust Silencer/muffler/baffle ideas

Thanks guys. Bond-o, I figured you had some experience in this area. I think I'd be fairly happy if I could just take the bite out of it a little, BUT it doesn't make senseto have to spend $200-300 for a slight difference. Jeep, I've heard of that FEA system. Some guys in another forum said it really makes a great impact on the noise. Seems like it would be awfully hard to adapt that to an I/O. My pipes exit above the outrive, so I could see that getting in the way too much. After sleeping on it a bit, I think I might trying to modify my existing tips to direct the noise downward. I rebuilt the boat a couple years ago, and I have intended to put a full swim platform on the transom, but have yet to do so. I'm thinking if I can do the full platform, and route the exhaust down through the platform, that might dampen the noise a fair amount. Then the exhaust would be exiting in the small gap between the water and the bottom of the platform. That would be the cheepest route at least. I suppose I could just use a couple of pvc elbows clamped on the tips to test it.

 

[BigBoatinOkie]

Re: Exhaust Silencer/muffler/baffle ideas

And yes Bond-o, Y pipe will go on mine as well if I have to pull the motor in the future.

 

[oldjeep]

Re: Exhaust Silencer/muffler/baffle ideas

http://www.monstermarinestore.com/productdetail.cfm?productid=1216&incat=24
http://www.knbsupply.com/insisy.html

 

[makonnen]

Re: Exhaust Silencer/muffler/baffle ideas

I've often thought about this too.

Mercruiser is a love-hate thing for me. On one hand, I love how they work... on the other hand, its obvious to me that businessmen and accountants had a say in the design. I'll get to the point, what is the point of having the exhaust Y pipe and routing the exahust through the leg? Why not a thru-hull or thru-transom? The raw water pickup should come through a thru hull too. On that note, why is the raw water pump on an Alpha drive INSIDE the lower leg? Why not an engine mounted accessory like the Bravo's? Trim switches, lube tube should come through a thru-transom.

The answer to all of that: it was a business decision. No boat manufacturer is going to buy Mercruiser drives if they have to do all that extra work to install them.

Ok, I've been also thining about a thru-hull or thru-transom exhaust system. Exhaust out the back of the transom and a 90 degree turn into the water since the transom is out of the water when planing.

Two things have been holding me back
(1) How do I design it so that when in operation, water doesn't get forced UP the exhaust system?
(2) What about the flapper / one way flappers??

 

[makonnen]

Re: Exhaust Silencer/muffler/baffle ideas

http://www.monstermarinestore.com/productdetail.cfm?productid=1216&incat=24
http://www.knbsupply.com/insisy.html

Thanks for the post ... but man, $500 for a one 90 degree SS pipes? Why don't I just buy some SS tube and go to an exhaust shop to bend it?

 

[achris]

Re: Exhaust Silencer/muffler/baffle ideas

I've often thought about this too.

Mercruiser is a love-hate thing for me. On one hand, I love how they work... on the other hand, its obvious to me that businessmen and accountants had a say in the design. I'll get to the point, what is the point of having the exhaust Y pipe and routing the exahust through the leg? Why not a thru-hull or thru-transom? The raw water pickup should come through a thru hull too. On that note, why is the raw water pump on an Alpha drive INSIDE the lower leg? Why not an engine mounted accessory like the Bravo's? Trim switches, lube tube should come through a thru-transom. ...

I'll try and answer some of these for you...

Mostly it's history, and a long time back... Basically a Mercruiser stern drive is just an outboard leg bolted to the back of the boat... That's why the water pump is in the leg... Legacy.... And you can buy engine mounted pumps for the Alphas...

Y-pipe exhaust system.... This is the only way to get exhaust NOISE and gasses out through the propeller and underwater.. If you have a read of many threads on thru-hull exhaust, many say they want to get rid of them, too noisy and y-pipe and through the drive is the ONLY way to do the job properly.....

As for trim senders and the lube tube, it's a lot easier to install and maintain a drive when everything is container in the one unit... It is not easier to pull the single 10 pin engine harness plug than to disconnect each wire from its individual place?

HTH,

Chris...

 

[BigBoatinOkie]

Re: Exhaust Silencer/muffler/baffle ideas

Thanks again for the replies. Oldjeep, the K&B silencers are ones that I have considered. Since those are for 4" exhaust, I would have to do some modifications to make it work. I suppose I could swage up to 4" exhaust hose and put in the K&B silencer, then swage back down to 3" into the tips. There might be enough room for that. Those monster marine turn downs are a bit pricey for my taste. The Y pipe is the best way to go, but it's too much trouble to pull the engine just to add the Y pipe. I'll just wait until I find a good excuse to drop in a 350 Chevy and do it then.