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Silent Thunder removal on newer FasTechs

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Silent Thunder removal on newer FasTechs

Old 04-15-2015, 07:28 AM
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The ST boxes are held in place by 4 bolts. 2 on the transom and 2 under the swim platform. Remove all 4 bolts and the box will come off, pretty easily, Might have to give it a little tug and pull..LOL.

Having a helper for this is useful, especially when it comes time to get the 2 transom thru-bolts that run into the engine compartment. Yes the rubber flappers are important, just an extra pre-caution to hopefully prevent any ingestion. Everyone seems to forget to add that you have to reinstall all 4 bolts you initially removed after ST box is off. Simply put a small bead of 4200 around the bolt head or hole, reinstall and tighten them down. As you snug them up the 4200 will push out around the bolt head guaranteeing a nice water tight seal.
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Old 04-16-2015, 08:53 PM
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Thanks again for the info. I'm looking forward to getting this rattle box off. Thanks guys.
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Old 04-26-2015, 06:44 PM
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Ok, got the ST box all removed and can't believe I didn't do this sooner. Lol. Now just curious, what does everyone do with the big box they removed ??
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Old 04-26-2015, 10:04 PM
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removed mine off my 271 and it is now sitting in my shed and will go with the boat if/when I sell it
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Old 04-27-2015, 07:15 AM
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Sat in the barn for 2 years before making it's way to the dump trailer. I got tired of moving it while looking for things. Some try to sell them, not sure what kind of luck they have. If you got the room i'd say keep it for now.
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Old 04-27-2015, 09:32 PM
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That's about what I figured guys. Thanks again. SJ
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Old 08-09-2018, 01:37 PM
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Well...
Time to bring this back to life Again!
Thinking about doing this on my 312. Does it really make the porpoising better?
I know taking weight off the back has to help, like getting Merc's heavy exhaust system off, but is it a big help in how the boat handles?
I like the idea of 6" slash cut stainless tips too for looks, but who has the best available now!

Last edited by MR.HAPPY; 08-10-2018 at 07:28 AM.
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Old 08-10-2018, 12:44 PM
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Other than the noise level you will see no noticeable difference in performance by removing the silent thunder or swapping out the exhaust manifolds. The porpoising is coming from the bottom of your hull. Formula boats are no where near perfect on the bottom. Take a 4 plus foot straight edge on the bottom of your boat and see how unflat the bottom is. Mine has gaps big enough to put your fingers under the straight edge. If you want to get rid of the porpoise have your hull blueprinted. Jeff wurl
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Old 08-14-2018, 12:19 PM
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Originally Posted by jwurl View Post
Other than the noise level you will see no noticeable difference in performance by removing the silent thunder or swapping out the exhaust manifolds. The porpoising is coming from the bottom of your hull. Formula boats are no where near perfect on the bottom. Take a 4 plus foot straight edge on the bottom of your boat and see how unflat the bottom is. Mine has gaps big enough to put your fingers under the straight edge. If you want to get rid of the porpoise have your hull blueprinted. Jeff wurl
Mercury told me that swapping to their headers (CMI) on my 6.2 MPI's would add 35-40 hp per side depending on the rpm's...
That & the weight savings should add up to some performance increase.
Was told to do a little head work to match the headers too, but still in the thinking stage for a winter project.
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Old 05-18-2020, 09:11 AM
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Resuscitating this beat-up horse. Just bought a 2000 271 FASTech. Bone stock. 1st mod is removal of Silent Thunder. But seems like it has been worked-on before. The two bolts on the port side seem to be from the outside bolting up into the swim platform. But the starboard side, has nuts with what seems as bolts (or perhaps studs?) coming from inside the boat/swim platform, down out through the ST contraption. Nuts then thread up to tighten. They are also not in the same relative locations as the "factory-looking" port side. Can someone please chime-in to confirm this is not the factory setup? My main concern is how to get to those bolts on the starboard side from the inside to pull them out once ST is removed. I guess I can leave them there and re-tighten with sealer but hate to have two bolts sticking out under the swim platform for no reason. Surely they'll generate a scar on my head at some point in the future...

I am still in rookie purgatory so cant post pics...
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