New to me 1993 336 is going in the water this week. The silent thunder exhaust has four drain plugs that go in the underside of the silent thunder unit. Should these stay plugged or should the plugs come out for more noise and maybe more performance? Has anyone experimented with this?

I removed the plugs from my 353 2001 fastech it did not
give anymore performance but it was loader.


this year i removed and put Eddie Marine switchable tips on
here is a photo with platform off. before tip install

I've tried mine both ways and didn't see ant difference in speed. But then I'm only running a single SBC not twin BBC's.

From what I under stand is that the water flow thriugh the rear area is used to keep the section coll. Hot exhaust gasses could damage the fiberglass baffles.

Causin Trouble, How much work was the conversion to the eddie marine switchables? I am contemplating droping the box on my 312 to do the same thing, The eddies look to be a little less money then the teagues, did you see any other results droping the silent thunder? Speed? RPM's? Thanks, Jeff

You can run with the small plugs out. There is more water going into the platform from the exhaust than can drain out fully from the plug holes. Therefore, there is no real concern of damaging the platform internals due to excessive heat.

However, this could be an issue if you have large cut-outs in the bottom of the platform. Those would have been put there by a previous owner, Formula didn't do that.

As for running with the small plugs out, it adds a bit more noise since the water level in the platform a is bit lower. But, I've never experienced any performance gain form it.

Thanks all - I think for now I will leave the plugs in and minimize the noise.

You should not notice any performance difference with or without the plugs in or out, box or no box. That's the beauty or Silent Thunder Exhaust, less noise with no loss of performance. Something I have seen happen though. Many who have cut larger holes on their box to drain even more water have been known to have problems with the box literally being rattled to death. The less water there is in the box causes excess vibrations and the box ends up making more noise than the exhaust does. If you want lots more noise, take the box off and put some tips on the transom. With the box in place, it will decrease noise levels 8-12 decibels from strait thru-hull exhaust noise.

I dropped the box factory captains call only used on demo but it is there if needed.(03 353) anybody need a box?