Bring the noise under water ?

[Mark Brandly]

Hi all
I have a 77 stamas, fresh water cooled 350 mercruiser with above water transom exhausts.The two 3" pipes have a marine inline mufflers and are about 4 feet long each, measured from the riser to the transom.
The boat is too noisy for me even though I do enjoy the rythmic sound of the v8.
My question... can I install an elbow piece on the outside and lead the exhaust under water.
It seems like a simple solution to me.

 

[JetBote]

Re: Bring the noise under water ?

Yes, but you'll still have the exhaust note when on plane.

 

[H20Rat]

Re: Bring the noise under water ?

http://www.freshairexhaust.com/

This system does exactly what you asking, but... I don't know if there is a model for I/O's, this is meant for inboards. It makes it safe to wakesurf/ride on the platform while operating the boat, it keeps the exhaust (and therefore CO2) underwater. noise reduction is a nice side benefit.

 

[Mark Brandly]

Re: Bring the noise under water ?

Thanks for the advice.
I must also ad some info.
The boat is a inboard, there is no y pipe, each exhaust manifold goes back and has its own exhaust pipe and tip.
The inline mufflers are new, about 12' long and did very little in terms of noise reduction.
My chief concern is water flowing back towards the engine (wake) or/and the vacuum created by the engine at idle or is the cooling water going to back up as it is recycled down the exhaust pipes into the ocean?
Looks and speed are not an issue. It is a 26' single engine (heavy) fishing boat and I keep the rpm's under 3000.
The tips are well covered by a large swim step which is about 6"above water.

 

[oldjeep]

Re: Bring the noise under water ?

Actually seen a couple ski boats with something that looks like this:

Guess it helps to keep the noise down for the neighbors during early AM ski sessions

Or something like this:
http://www.monstermarinestore.com/productdetail.cfm?productid=1216&incat=24

 

[H20Rat]

Re: Bring the noise under water ?

Thanks for the advice.
I must also ad some info.
The boat is a inboard, there is no y pipe, each exhaust manifold goes back and has its own exhaust pipe and tip.
.

for some reason i thought it was an i/o. in that case though, the system above (or a home made copy of it) will work perfectly.

 

[Chris1956]

Re: Bring the noise under water ?

Mark, You might repost in the I/O section.

I/Os are normally equipped with Y pipes and elbows. These direct the exhaust thru the prop. Because the boat is moving forward at speed, these exhausts are just as efficient as thru hull, but much quieter.

 

[oldjeep]

Re: Bring the noise under water ?

Mark, You might repost in the I/O section.

Why? He has an inboard - which is not an I/O

 

[Mark Brandly]

Re: Bring the noise under water ?

Thank you for the pic
This is going to work for me.
It really is about the neighbors too to run quite until I am past the breakwater.
thanks

 

[Chris1956]

Re: Bring the noise under water ?

Hey Jeep, He did say MerCruiser. I presumed that to be an I/O.

 

[Summer Fun]

Re: Bring the noise under water ?

These cut the noise down ... Reduces cruising noise by 60%. Reduces idling noise by 80% .

My friend bought a pair and said they REALLY do work.

http://www.knbsupply.com/insisy.html

 

[kenmyfam]

Re: Bring the noise under water ?

I think anything to quieten through hull exhaust is a good thing !!!

 

[scoutabout]

Re: Bring the noise under water ?

+1 -- kudos to you for your concern over noise. I too love the mellow rumble of a V8 but there are limits - especially when it's not my V8 that's rumbling. I think it's human nature but we generally seem to have a higher tolerance to our own noise as well as a lower expectation of its intrusiveness on others.

Good luck with your modification. Maybe post a before and after video if you are so inclined? Sounds like a nice boat.

 

[SangerTom]

Re: Bring the noise under water ?

I did a bunch of checking around a few weeks ago on the FAE system (the link someone listed) Couldn't find any negative comments and actually talked to the manufacturer. Not only does the noise drop but the reason they make it is to cut down carbon monoxide coming back into the boat (as they call it the station wagon effect). Cut carbon monoxide down 90% - coast guard tested. Runs around $490.

 

[oldjeep]

Re: Bring the noise under water ?

I did a bunch of checking around a few weeks ago on the FAE system (the link someone listed) Couldn't find any negative comments and actually talked to the manufacturer. Not only does the noise drop but the reason they make it is to cut down carbon monoxide coming back into the boat (as they call it the station wagon effect). Cut carbon monoxide down 90% - coast guard tested. Runs around $490.

Sounds like a good feature. I try to put my ski on as fast as I can when I'm on the deck of my father in laws Malibu - because of all the exhaust you inhale back there.

 

[Mark Brandly]

Re: Bring the noise under water ?

These inline silencers are cheap and look good,
They do not reduce the noise as much as advertised.
I installed them and hoped for big changes....but......they
MAY have taken off a tad but for sure not enough.
Today I dove below the swim step (brrrrrrr...Pacific), removed the two rubber flappers, measured the od on the tips.
Went to the hardware store, bought two beefy 90 degree rubber elbows from general plumbing...50 bucks for both.
Tomorrow is the big day.
A second dive will see the installation and hopefully the result of an exhaust noise only equaled by a Duffy.
Just kidding...Thanks for all the great replies!

 

[Mark Brandly]

Re: Bring the noise under water ?

Dear friends
It is done...I installed the rubber elbows. I drilled a quarter inch hole above the water line for all eventual vacuum issues.
The result is AMAZING...the exhaust sound is hardly audible and consists of water bubbles.
I am mighty proud and thankful for all your input.
It looks good too. The photo shows the fruits of my labor.
Yours
Mark

 

[ftl900]

Re: Bring the noise under water ?

Mark- I like that a lot, i also have the Merc 350 with twin thru-hull exhaust, and it's loud enough to be obnoxious.

What kind of rubber elbow is that?? I was thinking PVC or something like that may have been more durable.

 

[Mark Brandly]

Re: Bring the noise under water ?

Hi ftl
These are 90 degrees heavy rubber elbows I found in the hardware store plumbing section. The ID was 3.25", vs. the 3" on my exhaust tips. To fill the gap, I bought a coupler for pvc pipe ( a few feet down the isle), took the rubber out and cut them into two 1"strips (1/8" thick). I inserted them on the inside of the elbows with silicone to compensate for the gap. The next day I pushed the assembly over the tip and secured them with new stainless hose clamps.
I am over the top with the result.
Total cost 60 $/ 30 minutes of labor and two dives.
I am sure a rigid elbow would work too but the ones I found seemed perfect and they where on sale. (!8 $)
Good luck
Mark