Rattling silent thunder syndrome
 

OK, I know most will say to dump the silent thunder and go with regular thru hulls (and I will eventually), but is there a way to bondo/duct tape/super glue the thing to stop the rattling at idle? What is it that's rattling....baffles? Only happens on the port engine...the starboard side is fine...

Re: Rattling silent thunder syndrome
 

Is yours the newer integrated style platform or the pre-'92 big bolt on platform?

Re: Rattling silent thunder syndrome
 

If you look through the exhaust out let, flashlight required, you'll see a vertical baffel plate about 6-8" back. It is bonded to the top and sides. Yours probably came loose. You could take a long punch and a hammer to knock it off then pull it out. I think it'll fit through the opening.
A few of the guys here have taken a whole saw and opened the baffel to allow more flow.
Do a search on silent thunder and you'll see several threads on the topic.

With the current trend in noise regulation I'd rethink your idea of removing the platform and going with open pipes. You may find yourself having to by expensive mufflers.

Re: Rattling silent thunder syndrome
 

I've had three pre-'92 Formulas with the full platforms. Never had rattles on any. I think the rattle issue is more prevalant on the newer models that bolt-up under the integrated platform. Those Silent Thunder boxes are not as rigid and heavy-duty as the older full boards.

They are easier to remove and install though. Pull it off, find the loose culprit, fix it and put 'er back on.

Re: Rattling silent thunder syndrome
 

Here's what the inside will look like, assuming it's the same as the 95 336. Mine was split along the edge at the bottom of the pic and cracked in a couple of places. I took it off and never looked back. I'll try to fix it with 5200 and some small machine bolts if they decide to crack down on loud boats. Until then, she's staying loud and rattle free.

http://www.offshoreonly.com/forums/a...chmentid=77339

Re: Rattling silent thunder syndrome
 

Thanks for the responses!

Iggy, My boat is a '96 336, so it has the bolt-up-under-the-swim platform type. I'll try looking through the exhaust port to see if something is loose and easily removable.

Troutly, that's my end game, clamp on or thru bolt mufflers. I don't want to wake my neighbors up every time I start the engines.

Bill, how much does this thing weigh? If I can't see anything by looking through the outlets it's coming off for further investigation. I've got some leaking gaskets at the transom that need to be fixed anyway.

Re: Rattling silent thunder syndrome
 

I doubt yours is the same as mine. I have the bolt on swim platform not the same as yours. I believe they are constructed differently.
Yours should be like Bill272's.

Re: Rattling silent thunder syndrome
 

I had the same issue. Soot on the transom where I could see the exhaust was leaking past the platform. At the very bottom of the pic you can see a white crescent shaped spot. The seal between the exhaust chamber and outer shell was split there and that spot was rattleing and actually sanded a similar spot in the gelcoat on the boat. Took it off down to the fiberglass(I still need to fix that).

Anyway, to take it off I removed the ladder and the bolts off the back of the platform. It had some caulk that was holding it up, so I pulled down on it and it stayed there with a couple of inch gap at the back. I tied some clothesline to the outside bolt holes and secured it to the cleats up on he back to hold it while I took out the screws that held it to the transom brackets. Once those were off, I pulled it straight back. The gaskets around the exhaust will stick and the tips extend maybe an inch off the transom. Once it's clear of the adhesive gaskets and tips, it will come off and hang by the clothesline (I did that because I did it alone and wasn't sure how heavy it would be.) I'll guess it's weight to be 40-50#, more bulky than heavy. It would have been easier with a helper.

Re: Rattling silent thunder syndrome
 

The box on my 89 311 is close to 200 lbs or better.

One of the reasons it's not on the boat anymore.

Re: Rattling silent thunder syndrome
 

I NEVER heard a rattle .....then ........Outlaw just happened to mention a rattle .....THEN thats all I %#$#@$%^& could hear was rattle ..... :mad:
I had my platform off this winter and as Iggy sez the partitions were loose ..we glassed em back in and now quiet as a mouse .... :rolleyes: ....Mine is older style box .... A ***** to get off and on ......I would think the newer style would be ez fix ..

Re: Rattling silent thunder syndrome
 

Bill, I'll check it out this weekend, but why do you have to remove the ladder?

Re: Rattling silent thunder syndrome
 

Oops, my mistake. I was thinking that the ladder studs went through the silent thunder box, but looking at it it apparently does not. It's been a while since I took it off, and I was posting from my foggy memory of it. lol

Actually the ladder bolts were a problem for mine too. One of them hit a spot on one of the center exhaust chambers and made a hole there.

The 200 lb older style platform makes sense. The newer style is not structural at all and doesn't have to hold any weight, except for the water that fills it.

Re: Rattling silent thunder syndrome
 

OMG !!! I'm gonna have to listen for rattles as soon as I can splash it !!! Probably not 'til the middle of May the way work has been going. :mad:

Re: Rattling silent thunder syndrome
 

Here's an alternative to Silent Thunder box. Made out of 1" Starboard with 1" structural braces where brackets support and 1" structurals that run from side to side. Extends 30" from transom at widest point. Weight about 80 lbs.

With the transom mufflers noise level is about same as thunder and a lot more mellow.

We drew up design in Autocad and cut the Starboard with CNC laser cutter. We're thinking about marketing them if there's an interest.

So far no stains from exhausts on platform--about 6-8 hours running.

Re: Rattling silent thunder syndrome
 

Your platform looks very good...:drink:

Re: Rattling silent thunder syndrome
 

Had the same issue with the rattling box on my 336..... sounded like you were dragging a buch of cans behind you......also had the same thoughts about fixing it.....decided to take it off completely......the thru hulls sound really loud compared to the silent thunder box.......installed HPI transom mount mufflers and it still sounds great and looks great with the new muffler tips.

Re: Rattling silent thunder syndrome
 

** Update **

Forgot to update this thread earlier, but I found that the rattle was from an old & tired exhaust flapper, not the ST box. It was a much easier fix than taking the whole box off....

Re: Rattling silent thunder syndrome
 

FYI: I removed the Silent Thunder box off my 312. STILL RATTLES! Turns out the swim ladder is the culprit.