Had enough of the rattle and vibration of the silent thunder box so with a little help from jp2snowman pulled the boat at the CG station and removed the silent thunder box from my Formula 336. Removed all the bolts and the box would barely budge. Started prying the front edge with a large screwdriver and it slowly started to move. Thanks to Bill272 for the advice on attaching string from the box to the stern cleats to keep it from falling too far. Added 4" flapper tips to the existing thru hull fittings, cleaned up a lot of soot under the swim platform, and back in the water.

What I found.... all four donut gaskets were melted. The entire back top edge was de-laminated as well as the entire top port edge. The entire back port side corner was cracked top to bottom. Soot everywhere.

Now what..... The boat is definitely louder but sounds good to me. I plan to run as is for now and might add corsa muffler tips or Teague/ EMI switchable tips next year if I feel the need for a quieter boat when idling only.

Thanks to the board (and specifically this Formula section) for the great advice and guidance.

Welcome to the loud side!!! You gonna put rubber flappers on the tips to help avoid reversion?????

Rubbers are on for my protection.

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Every exhaust chamber was either de-laminated, cracked or BOTH.....

Okay, now you did it, just what I needed to inspire me to finally pull mine off. I'm replacing my manifolds/risers with the Eddie Marine - Thunder EMI units, thanks very very much to our own Trick Marine, for customer service that has set a new bar for "customer satisfaction". Fred, THANK YOU. The new exhaust just got here a couple of hours ago. No matter what you might need, CALL FRED FIRST.

Outlaw, did you get stainless risers or aluminum? If you got the stainless ones, block off the slots on top of the manifolds NOW with RTV or something similiar. Those manifolds while a nice buy can leak back into the exhaust chamber very easily and cause damage. Mine kept leaking quite a bit until I finally RTV'd the crap out of them. This offseason I had them welded shut, no more leaks.

Eddie Marine should make 2 verisons of the manifold, one for aluminum risers with water passages at the top, and one sealed shut and milled flat for stainless risers. I know of at least 3 people that have had leaks with these.

Went with the aluminum ones after a lot of discussion. Also saved me 130 lbs.

That's basically what mine looked like, but only on a couple of the chambers. Feels good having that rattleing thing off doesn't it?

It does feel great knowing that the rattling has stopped and that the exhaust is exiting the boat the way it should. There is definitely more noise ... I like it ...