Silent Thunder Exhaust
 

If I remove my exhaust box, will I

1. See a performance increase?

2. Have to change exhause tips?

3. Wish I'd left the damn thing alone to begin with?

382, Motors are stock HP500EFI (for now;) )

I'm running Innovation 600's in my 382 with Silent Thunder. When I spoke to the engine builder, his feelings were:

1. Probably not - the exhaust passages are pretty big.
2. Definitely.
3. Probably, but it depends on your tastes.

I have a 271 with a 500EFI, I took it off last year after running with it for 2 years. Think I may have seen some increase in speed, but it probably has more to do with getting rid of the weight than reducing backpressure.

It is definetly louder, but I have Silent Choice so it is not a bother when in a harbor. I will say that there was not much of a noise difference at speed with or without the Silent Thunder, it's all at idle.

As far as whether I should have left it alone, as was said above, it all depends upon your tastes. I can make poeple jump when that 500EFI comes to life with the Silent Choice off, but that is generally just plain rude (although fun when in the right crowd).

You will have to get new exhaust tips, I used Eddie Marine SS angle cut tips.

:cool: :p :D

On of our members modified his Silent Thunder system by removing the internal baffles and enlarging the outlets and making new stainless exhaust rings and flappers.
I think I still have his pictures and details at home. If so I'll send them to you.
The problem with the Silent Thunder is that it will only support just so much horsepower before the exhaust pressure begins to blow out the transom seals. I don't remember what that limit is.

Many of our customers remove the Silent Thunder and none of them have changed the exhaust tips. The important thing is to add the external rubber flappers on the existing tips. Haven't noticed a performance increase,guess it's just a noise thing for some. But it's easy to switch back if you get tired of the noise. Don't fill the holes,just put the bolts back in and your're ready when you want to reinstall.

Box is out of here
 

Gonna pull the box off next week, will see about the tips then.

Thanks for all the responses:cool: :D :D

silent thunder
 

Iggy,
Can you email me that info and pics as well?
Thanks, Craig


Also, does anyone know about how much HP it takes to blow out the transom seal gasket. I'm running about 470 HP and mine leaks a little. That shouldn't do it-must be the age (1990).How much trouble is it to replace the seal?
Would running with the plugs in the bottom of the platform out cause it to not leak due to less pressure?

Craig,
I have the pics on my home computer (I think). I'll let you know.
As far as replacing the seals, the entire platform has to be removed first. I think it's only four or six bolts.
I've heard of some that were all but impossible to break loose.
While it's off you should check the plywood bulkhead inside the platform, where it meets the transom, for rot. I understand it's pretty common.
I know I'll have to replace my seals some time soon. If I stand on the platform while the engine is running it leaks exhaust around the seals at times.

Hot Water
 

Send me your e-mail address so I can forward a copy of the platform mods.
Use the address that's in my profile and I'll send them out first thing tomorrow.

Sorry guys I seem to have lost them.
I wrote the person who sent them to me and I hope to hear from him soon.
Will let you know what happens.

Hotwater, I've run the boat both ways, with and without the Silent Thunder.

What I ended up doing to address the noise issue was to cut four 4 1/2 inch holes in the back half. on the bottom of the Silent Thunder box. Makes it a little louder but keeps you from getting hassled by the noise police.

The other thing it does is relieve the back pressure in the box. Mine was actually starting to break apart from the pressure, and would rattle. I think I remember Phanthom Chaos also having a problem with the box on his 312 coming apart.

As far as replacing the Tips, you do not have to replace them, the ones that are on the boat will work fine.

Performance wise I did'nt notice any difference without the box as compared to with the box, even before I put the holes in the bottom of the Silent Thunder.

I took mine off because it rattled from the fiberglass broken out at the sides. I don't think that there is a magical horsepower number that dictates when it happens. I have stock 502 Mags with the plugs removed from the platform and still had it blow out.

If you just need to fix your "seals", it's just a material similar to foam door caulking. You can find it at any hardware store.

Now that I have ran without it, I don't know why I didn't do it a long time ago. The tips that come stock (93 303SR1) are cast pieces and not Stainless steel. They sound much better than the S.S. I added the internal flappers and external flappers just to be on the safe side.

Bottom line is: I think it sounds great and it's not as loud as a regular boat with Stainless tips.

If you do remove it, you need to back out the screws that hold on the rub rail. Use a wide blade putty knife to pry it loose, and take your time. Drop the back loose first and let the tips hold the front. get a friend to help you. It is HEAVY.

I can't believe that removing that much weight didn't make much difference but, I'm sure it all adds up.

Good luck,
Bob

I'd like specs on the platform mods too. I've noticed the twin 930hp 311 in the classifieds is running the Silent Thunder platform still. I'm going to be adding my prochargers sometime soon (if not real soon it may be this fall) and I will be taking the platform off (adding imco boxes) so mods can be done then.

[email protected]

Keep one thing in mind, the silent thunder boxes are different on 311's as compared to later model boats like the 303's,336's and 353's. The older model boats the box is part of the platform, newer models it's a seperate unit.

I have a silent thunder platform for a 311 if anyone is interested

I have been running my '98 252LS with the plugs out of the silent thunder last season and was contemplating drilling two more holes into it.... would that make the exhaust run to hot? Where to drill.... what is inside the platform?

Great boat, just too quiet when on plane. :cool:

Take it off!!!!!
 

You will pick up about 10 - 12 MPH by loosing the weight and because it sounds faster!!!!!!

Really now.............I had to have the one on my 312 replace twice because it started to crack both times. Seemed like it was a little thin in some areas. I ended up removing it and installing straight tips (actually Dick Simon Marine didi it) with internal flappers and external rubber flappers. Made it sound like a whole boat.

On my 382, it has the extention boxes do it didn't have the Silent Thunder system, it had the factory Corsa mufflers. Before I took delivery, I had DSM remove and replace the Corsa mufflers with straight pipes with a 45 degree tip..............looks bad ass. Sounds bad ass. Is bad ass. Besides, I have the Captains Choice when I want it to be more quite.

45 degree
 

No Silent Thunder!!!!!!!!!!

Hell Yeah!
 

(just my opinion)

PhantomChaos
 

I agree, they do look alot better without the box. And a 10 -12 mph gain to boot, hell if I crank the tunes I could probably get another 2mph.:D :D


Why dont you drag that bad boy up to Northern Calif. for our third annual Big Cat Poker Run sponsored by Bob Teague on May 18th. We expect about 90 - 100 boats.:cool:

I took the silent thunder off of my 271 last year. It sounds much better, no more rumbling and rattling noise. I used the tips that were already installed and just added some rubber flappers on the outside. As far as performance, I didn't really see any change.:D

Its off and I like it
 

Removed my Silent Thunder box Sunday. 4 bolts two guys and it fell right off. The tips are fine just need external flaps. No sound ordinance here. The weight of that box is equal to a grown man. I am going to like having it off.

Just make sure you put on the external flappers before you run it and you will be fine.

MagicFloat
 

Will do.

Thanks

Silent Thunder Exhaust
 

I have a 1988 Formula SR-1 22.3 LS and I would like to buy an Exhaust box. The box I have now is broken at the eye loop and I don't know how to repair it? :evilb: If any one can help.
Please RP

311 sr1
 

I have an 88 311 sr1 with trs setup. I would like to know if any of you guys have done this to a similar boat. end goal is to replace with an extreme platform. what external flappers for trs setup....i believe i have 4 1/2 inch tips? should sound sweet with imco exhaust

Ralph
I had a local boat figerglass guy fix mine on my 272. same issue as you. cracked at teh eyebolts. due to the front surface of the plaform rotting ( it is wood). we repalced the whole front with marine plywood, and sealed it, and then regelcoated the showside around the top edge and the attachemnt areas

like new now

about $1000 if i remember

I can send you a few pics if you give me your email address.

I'm at robert.hamelink "at" jci.com ( no spaces)


Ramb

pull the box, add flappers, and make some noise. '02 353, 500EFIs, Corsa when I need it. I'm the only powerboat in a private marina of blowboaters. I take great joy in heading to the marina on Wednesday's (Regatta day) and firin' 'em up and providing a nice bass note rumble to their festivities :D :evilb: :D :evilb:

menace to society...

Agreed, and now he thinks it's the tits to harass the poor blow boaters. Guess you need to take your victorys where you can. :rolleyes: Wait till he has to tangle with the Sea Ray powerboaters in August, may get put in his place then.