More Thunder Less Silent
 

A friend of the family had a 272 SR1. He cut 4.5 inche holes into the bottom of the swim platform. I thought it was to make it louder but, read on one thread that someone did this to his 292 to help let out more exhaust to help out his engines. Does anyone know if it makes a noise difference as well. Does it work on 242LS as well? Also does anyone have pics of modified baffles without taking off the swim platform?

Re: More Thunder Less Silent
 

My 311 has 4" holes in the platform bottom. 2 in the center and 1 on each end. It is much louder than stock- 108 dB on one engine 113 with both running. The holes allow all the water to drain so there is very little silencing.

Re: More Thunder Less Silent
 

I cut big rectangular holes in the bottom of my silent thunder, as large as possible approximately 6 x 9 inches or something like that.

Then I dropped the entire platform when I swapped out my exhaust to EMI Thunder aluminum units with Stainless Marine Superflapper Tips.

Re: More Thunder Less Silent
 

I cut 3-1/4" holes in the bottom of the box, 2 holes directly in line with each exhaust outlet. Didn't go into the box and remove the baffles, felt it wasn't necessary with double sets of holes. As insptech said, it allows all the water to drain out when your running, increases the noise level (didn't measure) both at idle and at cruise. Also allows the engine to breathe a little easier. I also just put EMI Thunder.

Re: More Thunder Less Silent
 

could some one maybe take a few pics to get an idea what,where and how much. i too would like to "thunder" it up a little. but cant go too crazy because of the sound police. :mad:
Thanks for the help

Re: More Thunder Less Silent
 

You can open up the bottom of the box, bigger circular holes, big honkin' rectangular holes like I did, and the bottom of the box doesn't really completely clear the water until about 35mph or a little more. On mine as it was on plane and gaining speed, all of a sudden it got considerably louder, that's when the box was completely out of the water. It also tends to act a a big "center plane" when coming up on plane. I noticed a big difference when I removed my box.

So as long as your going slow or idling, you could remove about all of the bottom of the box and the sound police ain't gonna know....:drink: :D

Re: More Thunder Less Silent
 

did you guys cut the holes in the bottom of the port and starboard sides. or under the flat part tucked up where the exhaust enters the box initially?(above the drive.)i already have the little factory holes under the port and starboard side. is that the right area? i would like it to sound better idling too. it sounds a little toilet bowlish idling :eek: . hell, maybe ill do what rambuncious did and run pipes right through it! that'll fix it :evilb:

Re: More Thunder Less Silent
 

In the bottom of the port and starboard sides, just in front of the rectangular factory exhaust ports. You shaould also have a similar section in the center of the platform as well. Drill the holes in line with the existing exhaust ports.

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thanks again. time to break out the holes saw, and maybe the sawzall! :eek:

Re: More Thunder Less Silent
 

Actually "rambunctious " here

before you cut big hoes in your show surface of yoru swim platform , I have two other options

1)

remove or cut out the baffle plates that are about 5" from teh square tips. I did this with a very long saw zall blade, through the square tip openings. start at teh bottom ( 1" gap exists, cut up, over, and down, like a dog house hole.

this makes it louder, but still muffled


2) plumb from the thru hull flangess to the square tips with marine exhaust hose and some stainless elbows
( takes some fabricating , but sounds awesome now)
search my posts to find info and pics


Rambunctious

Re: More Thunder Less Silent
 

I like that option better, too...I think! :p

So, what is behind the "baffle"? When I open the flapper, is the "baffle" the "wall" of fiberglass you see there? I appears that the exhaust has to be directed UNDER that so-called "baffle". What you are proposing is to straighten out the exhaust flow from having to go under the "baffle" to straight thru the "baffle" and maybe a little exhaust may still find its way under the "baffle" as that part will not be cut out.

Could you use a holesaw to just cut out a decent size circle?

And in the end, this process doesn't really help performance, only makes the boat sound better, right?

Re: More Thunder Less Silent
 

Here are the pics of the mod that I did to the underside of the swim platform. These holes are not visiblewhen in the water and running. Only visible when on a lift from underneath or on a rack.

Results are not only louder exhaust, but any relief of backpressure for the exhaust is always a good thing.

Re: More Thunder Less Silent
 

yes. but the hole saw size is what you can get past the square tip
I had tried that first, had a dull hole saw. birned my finger touching it. then went to a long blade and the project was done in 30 seconds.

the baffle is this fiberglass wall. the silent thunder patnet is the exhaust bubbling under this wall.
cut the wall out and it will sound better.
no perf improvement

Ramb

Re: More Thunder Less Silent
 

Thanks, Ramb! :drink:

Re: More Thunder Less Silent
 

treads,

If the boat is stationery and is being subjected to back swell is there any chance that water could be ingested into the motors now there is more chance of water entering the platform because of the holes?

Re: More Thunder Less Silent
 

Good Question!

Re: More Thunder Less Silent
 

in my opinion, it isn't any more chance than a classic flat transom boat with short thru hull tips and no swim platform.

the formula thru hulls do have butterflys at the transom , but mine, like many others have mentioned, are burned out.
there is a decent slope to the exhaust, especially at waterline angle of these boats when floating.

ramb

Re: More Thunder Less Silent
 

Waterfoul,

I would agree, no worse than thru exhaust without platform.

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I don't think the holes in the bottom would pose much of a problem, but cutting out the baffles seem like they could!

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I removed my baffles and cut drilled 3 more 5/8 holes in the bottom of my box and have not had an issue :D With that being said i do take it easy when coming off plane.

Re: More Thunder Less Silent
 

i took off the square tips(For larger access) and put 3 , 2-1/8 holes in the baffle wall. it took about 5 min. and the wall is paper thin. it sounds better at idle, but the rubber square flappers still cause it to be quite muffled. time to put some holes in the bottom, hopefully i wont get some vibration issues that some people have posted :eek: :eek:

Anyone notice vibration at low rpm when cutting holes in bottom of platform??

Also has anyone cut the holes on the inside parts of the swim platform on a twin and have pics?

The ladder always vibrates. The platform will vibrate if you have loose baffles.

Sweet. Thanks for the quick responses especially with the pm's I sent Lastnight. I do like the look of box. This is my second boat and really love the noise!!

I too wanted more sound, so last season I cut the baffles out(1987 223ls). As stated before, slight idle improvement in the water, and louder cruising. However, wanted more sound, so glassed over the original exits and cut the new holes inline with the original transom oulets. Heres a pic to give ya an idea, if u look in my album in my 'hey ya'll' thread , you can find a series of pics on where i moved the outlets and built new inner walls to force all water an exhaust thru new outlets. I also drilled 3 5/8" holes in new chambers for drainage. Probaly be another month before boat is assembled and find out if it was worth the effort.
https://m.facebook.com/photo.php?fbi...45056&refid=13

let us know how it works. i have been thinking of doing something like that for a while .

This is how my 242SS used to sound with the 454 genV 330 HP

I have two small holes, they are located close to the transom on each side of the platform

http://www.youtube.com/watch?v=L5wXZ229Iwo

moparjet- I will post a vid idling in yard and on water once I get het together.

Monac20- Its funny you posted that, actually watched that vid on youtube earlier today, was looking at swim platforms to get an idea of how to paint the color breaks. Sounds Good!

This is for sure more thunder ;-)

http://www.youtube.com/watch?v=c6smT8bNJiQ


Not my boat or my video, but very nice boat :-)

Try searching for exhaust242 old post.

Rocco is drumming up the past. You did some searching for this one. I started this thread back in 2006 as a senior in college, 2 years before buying my Formula. I've all but forgotten about these old posts of mine.

lol...just bought my 311 and before i started hacking away at it wanted to be sure....this is an awesome site!!

Congrats on the 311. Love the vintage SR-1s. Even being 20+ years old, they still turn heads when out on the water.

Had I not have found or gotten such a good deal on my 292 fastech, I would probably have ended up in a 272 or 292 SR-1..

So anyone have any new updates on their silent thunder updates??

My 242's platform is sitting in my backyard, unfinished. I was plumbing the exhaust through the platodorm. If anyone wants its... come get it!!

where are you from?

I'm in Virginia Beach, VA.

Shoot. Solid 13 hour drive each way for me haha. My 242 platform has a crack.