Audiofn

TTT for Formula

Formula Outlaw

I have an 89' 311 with basic 454 mags. I cut my baffles out using the specialized Porter Cable saz all, then I enlarged the circular holes at the bottom of the box into hugh friggin rectangular holes. It sounds better at idles, when the boat comes up on plane and the box comes out of the water gets much throatier, and spinning the original 23 inch Mirage props, gained 300 rpms on the top end with the modifications. I've read where some people have done this and did not see any more rpms but all I can say is I did.

C_Spray

iTrader: (2)

I've got this system on the drawing board, but it has to be done in SS tubing. I'll put a sketch together and post it tonight or tomorrow. It's a 3-way system: Straight-through / Muffled / Underwater. Brownie at Stainless Marine is helping me with it.

CayFomula

I removed my Silent Thunder exhaust on an 89 272SR1 an picked up nearly 7mph on GPS to a top speed of 90.2mph. I am running 454Mags with Dart Pro1 CNC'd heads and Whipples so I was probably producing more back-pressure than normal. In addition to the speed increase my boost actually dropped 2lbs.

lv92780

Hey guys I am new to Formula I have a 1992 242 LS with a 502 runs great only400 hrs if I take out those rubber plugs in the bottom of the swimplatform the silent thunder exhaust will sound alittle better

lv92780

Prop Question I have 1992 242 with a 502 takes long time to come on plane with 5 people running 23p s/s prop should i go to a 26p to get out of the hole quicker or will i lose alittle top end

Rambunctious

lv92780

taking the plugs out will make it a little louder, but mroe water flows than can drail out the small holes under full throttle.

if you wanted to make it sound better, you could cut out the baffle plates that are midway inside the silent thunder box.
i did this early on and it sounds nice. search under my logon and i even have a simle scetch on what it looks like inside

a long bladed sawzaw and in 30 seconds you are making more noise

regarding prop pitch, the number equates to theoretical travel (in inches) a blade makes in one revolution. ie the boat travels either 23" or 26" in one prop rotation.

so a 26 would be more pitch, making it more difficult to get on plane ( like starting in 3rd gear)

the key is getting on plane in sufficient time , and running full throttle at your engines peak rpm to get the top speed

so with the 502 you shoudl be at wide open with your most common amount of passengers and fuel, and be at about 4800 rpm

now if your engine is spinning up too much rpm with the full load, then maybe a bigger diameter prop may be needed. I assumed the engine was just lugging with 5 people....
hope this helps

Ramb

Waterdogs

Is the 23P a 3 or 4 blade prop?