No more Silent Thunder boxes...
 

The wife and I took a run up to Decatur Indiana and got a tour of the Formula factory yesterday. Of course I was checking out some of the brand spanking new '06 Fastechs coming off the production line and noticed no Silent Thunder boxes, just nice Corsa tips with rubber flaps. I asked our tour guide and he said Silent Thurnder boxes are no more...

Inside the engine compartment are polished Corsa "Quick & Quite" exhaust. I assume there are some muffler tips as well. Reading on the Corsa website it appears the exhaust runs both out the transom and through the prop. Looks like a nice system. Wonder how it sounds and performs compared to the box?

Re: No more Silent Thunder boxes...
 

I never thought the'd drop that feature.
It's surprising that they went with a switchable system, which is illegal in many states.

Re: No more Silent Thunder boxes...
 

The "box" was definitely one of Formula's hallmarks, no one else had/has a system like that. I'm also surprised they dropped it. Of course, almost everyone I know dumped the box.

I personally like the looks of the older boxes/platforms. However, I did just get done last night gutting the baffles though! :D

Re: No more Silent Thunder boxes...
 

they most likely found they could buy the Corsa transom mount mufflers in quantity cheaper than they could lay-up the box enclosures.

savings on the raw tips they used behind the box
Plus take out the labor of installing the box.

The labor of installing the Corsa's on the transom instead of the raw tips stays about the same.

The mufflers are now the standard
switchable diverters to thru hub is an option as it always was, I believe.

Re: No more Silent Thunder boxes...
 

Corsa systems on other boats I have seen are not switchable, and run through the tips and the prop simultaneously. In my opinion, it is quieter than both the older bolt on platforms and the newer style box ones. A friends boat that has this corsa system sounds more vaccum cleaner like than raw. Personally I don't like it. Hopefully Formula will have a custom tuned version of it, otherwise I'd be installing a switchable system very quickly.

Re: No more Silent Thunder boxes...
 

Are you sure about this? I've never known a system that continuosly diverts through both the transom AND the prop. It's always one or the other.

Re: No more Silent Thunder boxes...
 

FAQ on Corsa's website - see "permanently open diverter" below

1. What is a CORSA Performance exhaust system?

CORSA Exhaust System consists of three major components:

A. Diverters - A diverter splits the exhaust into two exit paths: straight out the hull and down through the propeller. CORSA offers two styles of diverters: a permanently open diverter and a solenoid operated (Captain’s Callä) diverter that offers the choice of thru-hull, or a through prop exhaust exits at the flip of a switch.

Most "factory stock" installations have the permanently open diverter so there is no legal issues in some states where it is outlawed.

Re: No more Silent Thunder boxes...
 

Very interesting. Thank you, I did not know that. :cool:

Re: No more Silent Thunder boxes...
 

The Captains Call is a must! It's a $2,100.00 (list) option, but
worth the money. I can tell a difference with the performance when it's turned on.(Or maybe it's just me)

Re: No more Silent Thunder boxes...
 

I agree with getting rid of the box. I took it off of my 99 271 because it vibrated my ladder on the swim platform and made a rumbling sound. The Captains Call exhaust is the way to go. :D

Re: No more Silent Thunder boxes...
 

an hour at most to remove the under-platform enclosure.

20 minutes if you have a second set of hands to hold the wrench on the inside.

the two brackets between the drives are thru-bolted, w/ nyloc nuts no less. :rolleyes:

I did it alone with some ingenuity. :cool:

Re: No more Silent Thunder boxes...
 

you guys are making this waaaay too complicated.

#1. Corsa transom-mount mufflers have taken the place of the silent thunder box for the muffling of the "thru-transom" exhaust. This is now standard.
See my post above, it's most likely about $$.

#2. a "diverter" or "switchable" system (Corsa's version of "silent choice") downstrem of the risers is an option...just as it has been for a few years now.

class dismissed!! :p

Re: No more Silent Thunder boxes...
 

Hang on, teacher, got a question. Is there any performance advantage to switchable system? I believe they all have the Corsa mufflers. If I understand correctly, with the switchable system "open" you get flow through the transom and the hub. This is just like it would flow/sound with a non-switchable system. So to me the only advantage of the Captains Call is you can "close" the through transom exhaust path and force all the flow through the hub to get reeaaalllly quite. No performance advantage.

Re: No more Silent Thunder boxes...
 

in terms of performance there are only disadvantages to be had...
if you don't use the system responsibly.

#1 Operating the system "closed" (ie: thru hub) there is a relative loss of HP (on a performance oriented engine) above say 2500-3000 RPM.

#2 There is a greater risk of reversion at the afformentioned RPM and above due to the limited flow, bends and turns of the "wishbone" pipe that directs exhaust (and the water) to the transom assembly. The relatively small diameter of the exhaust bellows, and the small passage in the drive also contribute to this.

exhuast will attempt to find the path of least resistance.

Therefore, in my experience, in the closed (thru-prop) position...there always seems to be some leakage past the diverter to the thru-hulls (10-20%).

The "open" position (thru-hull) is more of a sure thing (damn near 100%) as it is the easiest path for the exhaust to take.

you get extra credit!

Re: No more Silent Thunder boxes...
 

Cliff's notes on Exhaust 101. All 06 Fastechs have thru hull exhaust with Corsa Mufflers as std equipment. Sound is about the same as the previous Silent Thunder but without the extra weight of the water in the old pan. It is a nice throaty rumble but legal in all states. As an option,Corsa Captain's Call,an electrically switchable system with the Merc Y-pipe that sends the exhaust thru the prop for quiet opertation like a family boat with normal thru prop exhaust. But as Rippem said,there is some leakage around the valves and a little will leak thru the mufflers,no big deal. Downside of Captn's Call? Cost#1,Illegal in many states #2. #2 is not a big deal,haven't heard of any tickets for it but is is on the books and could at some point be a problem. Bottom line if you like a nice throaty sound that is legal,order the boat standard. If you want the option of making the boat quieter as conditions dictate,spend the money on Captn's Call.The only performance decrease will be when you close it up,but you have the switch at your command to open it back up. There will be a test later for extra points :drink:

Re: No more Silent Thunder boxes...
 

Robert, does my post (#4) seem reasonable to you?

and I forgot to mention the potential cost of warranty on the enclosure if it splits/cracks/delams.

take a look at my '06. :D

Re: No more Silent Thunder boxes...
 

Post #4 makes sense with one exception. Formula is not particularly driven by cost savings,if they were they would not be Formula :p I think that since so many 353/382 boats were ordered with Stellings where the pan would not fit,and the knowledge that so many owners were removing the pan anyway made them go this direction.Silent Thunder was a great idea years ago when it was so much better than a bolt on swim platform,but times have changed and Formula has changed with it. If anybody wants a 2006 with the pan,call me,I have lots of them stacked up from customers that have removed them,but I doubt I will have many takers. I applaude Formula for the change,it was needed and they stepped up. :D

Re: No more Silent Thunder boxes...
 

Thanks for clearing that up guys. I'm new to this picture posting but will see how this goes. Should be a picture of the stern of a 292. Took this picture Tuesday at the Formula plant.

Re: No more Silent Thunder boxes...
 

View of a 292 under construction. You can see the Corsa Y-pipes.

Re: No more Silent Thunder boxes...
 

Better view.

Re: No more Silent Thunder boxes...
 

and a bare 353 deck in the background. :)

Re: No more Silent Thunder boxes...
 

That may be my new Sport :p

Re: No more Silent Thunder boxes...
 

Wouldn't it be legal in all states if the thru hull was muffled too?

Re: No more Silent Thunder boxes...
 

only legal if it meets DB requirements.

Re: No more Silent Thunder boxes...
 

Exhaust 101-B.The Porters do not like loud boats and will not build one that will not meet requirements in all states,hence the Corsa mufflers. They work well with a a nice legal rumble sound.Captn's Call has never been an issue in states that outlaw "exhaust cutout devices" because the boats meet DB requirements in all cases,open or closed.

Re: No more Silent Thunder boxes...
 

The y-pipe with or without the switchable option is a definite plus if done properly to avoid reversion jissues (reversion is less of an issue on newer efi/IAC engines, still highly dependent on the cam). It reduces backpressure and db level over the same muffler system without the extra path. It allows more overall flow area than just a transom mounted muffler and more internal volume to buffer exhaust pulses (lower db level and peak pressure). I have seen the difference on a boat that had older Gil clamp on mufflers with silent choice. The silent choice was removed and there was a definite speed loss. Put the silent choice back in, speed came back. Keep in mind that the silent choice valve, open or closed, allows exhaust to go out through the drive as an extra way for backpressure to bleed off. The biggest problem on performance engines and exhaust is that it usually requires the water dump earlier in the tailpipe, therefore it's easier for reversion to be an issue.

Re: No more Silent Thunder boxes...
 

I just received this info from Formula.All 06 Fastechs have as std equipment Corsa Quick and Quite systems. This is thru hull tips with mufflers plus the Y-pipe. It is NOT switchable,that is an option,as always. I'm not sure of all the reasons behind it but I don't see any negatives here. One positive I can see, if someone buys a standard 06 and wants to add Captn's Call later,it will be much easier and cheaper to do.

Re: No more Silent Thunder boxes...
 

what are those motors ?

Re: No more Silent Thunder boxes...
 

Those are MX 6.2 MPI's, optional engines for the 292 Fastech. GM small blocks. 6.2 liter / 377 cubic inch (4.00" bore X 3.75" stroke) and rated at 320 hp at the prop. Click on the link for more info.

http://www.mercurymarine.com/mx_6.2_mpi_sd_-_320_hp

Re: No more Silent Thunder boxes...
 

My 353 does not have the box, only the corsa mufflers but unfortunately it still vibrates my swim ladder at idle. Kind of annoying :rolleyes:

Re: No more Silent Thunder boxes...
 

I ran the Silent Thunder box from 2000 to 2004, but was continuously breaking brakets with the vibrations from my Innovation 600's. Once I made stronger brackets, I started breaking the bolts!

This is a set of custom, externally-switchable exhaust tips that CORSA made for me. Since my engines have Stellings headers, the through-hub option was not available to me. When the flaps are shut, the exhaust is diverted out of the slots in the bottom of the mufflers. I cut the slots myself, but made them too big, so there is very little reduction in noise. I plan to re-do the system over the winter so that the diverted exhaust runs down the transom and exits underwater. These mufflers have a very nice rumble to them. The engines were VERY loud with straight headers and flappers.

Re: No more Silent Thunder boxes...
 

have you got the foam mat on the floor of thw ladder compartment?
never hear a peep from mine.
no rattles whatsoever.

Re: No more Silent Thunder boxes...
 

I do have the mat. I tightened all the screws up back in July as well, but that did not help much. I wonder if the mat needs replacing?

Re: No more Silent Thunder boxes...
 

Yep. The headers stick through the transom at a 20 degree down angle. If I had installed clamp-on mufflers, they'd be buried in the water off plane, and I was worried about inversion (and the looks). I made up the 14 degree spacers, bolted them to the transom, and then bolted the mufflers to the spacers. The mufflers are almost 22" long, so I made up the stainless brackets, installed threaded brass bushings into the fiberglass, bolted them up with rubber bushings and clamped the mufflers to the brackets with t-bolt band clamps. Solid as a rock. Hated working with the stainless, but loved the way it looks. Here's a closeup.

Re: No more Silent Thunder boxes...
 

I agree. Leave it to Chuck to come up with something that innovative.

Re: No more Silent Thunder boxes...
 

My silent thunder box was a BIT(H to get off. Ended up having to mill a 2x4 narrowing it down to a basic "point" after about five ft. It was almost at some point, someone had reinstalled the box with 5200 or something similar. It was NOT your typical gasket sealing material. Anyway I had to get a 3 lb. maul and hammer the wedge between the box and the stern of the boat, VERY CAREFULLY. Took me about an hour but it worked great. Couldn't believe how heavy that sucker was.

And yes, all the bolts were out......:eek: :D :D

It wasn't leaking though.

We don't have sound issues down here. 90% of offshore boats in our neck of the woods run "straight thrus" with no problems with law enforcement.

Guess the Porters would not like my boat, it ain't that quiet anymore.

Everyone who has seen the boat, and knows boats, has really complimented me on what I have done.

Re: No more Silent Thunder boxes...
 

Looks nice Fred. :cool:

alot more room to cook and clean back there now huh? :p

Re: No more Silent Thunder boxes...
 

Looks good Fred....:drink: :drink:

Sounds better too....:drink: :drink:

Re: No more Silent Thunder boxes...
 

Fred,
If the boat looked that good when I had it I'd still have it! Nice job!!