Formula "Silent Thunder" modification???
 

Hey everybody, bran new to this site, been following it for a while and figured I'd give it a shot. I have a question about the Silent Thunder system on my 1989 Formula 242ls... It is the 454/Bravo 1 set up, and that Silent Thunder is WAY to quiet for me, but everybody's solution seems to be to remove the swim platform and just do thru-hull... I really want to keep my swim platform but also want that thru-hull sound, so I think what I am going to do is get a nice set of Trumpet style tips, and mount them on the underside of the swim platform, and connect them to the exhaust outlets that come through the transom with some exhaust tubing. I think it will sound a lot better at idle, but also won't be too loud inside the boat under full throttle cause the sound will be coming out underneath the platform. I have no doubts that I will be able to make it look really good, I've done more fabricating in my life time then I care to admit, but my question is: What size is the exhaust outlet that comes through the transom? I'm assuming 3 1/2 or 4"?? I would like to know before I start taking everything apart cause I'd like to have all the parts in hand so I can knock it all out at once, so obviously I need to know the size so I can order the correct tips. I appreciate anyone's input who would know for sure the size??? Thanks in advance

Mine is 4" through hull, I think that is standard for most thu hull systems. You could also remove the swim deck and put on an aftermarket deck on and maybe utilize the same holes with just some new tips I'm not familiar with the trumpet style tips so ill have to check that out to fully understand your idea.

Dean

The stock tips are 4". I just finished modding mine.

http://www.youtube.com/watch?feature=player_embedded&v=9fAoxA07PJo http://i2.photobucket.com/albums/y48...386E5ED7D8.jpg

I used these tips.
http://www.hardin-marine.com/p-12590...haust-tip.aspx

Gm I did this same thing a few years ago to my 242 I ran the exhaust thru the platform with ss tubing and hooked it up to 4`` round flush tips with internal flapper, if you go to the Formula section I`ll try to find it I have some pics.

mark

I bet the flush tips look cool! Does the water hush your exhaust for a few seconds when you stop?

If you are going straight out the back like that you should invest in rubber flaps for the exhaust, With the sides and top filled in by the platform, you can stuff so much water up in there while backing that it could fill the engine through the exhaust. That is one of the things the silent thunder prevents.

Wow, thank you everybody!! Those pics/videos are EXACTLY what I had in mind, that thing looks and sounds great! I'm gonna get tips with internal flappers in them just cause I know how close to the water line that is. I was wanting to buy the flush mounted oval tips that they sell as "side exhaust" for boats, and mount them up and down for the flush look, but damn those things are pricey! I'm glad to see that it worked out good on your Formula (fischan), cause I figured I'd be going into this blind since it seems like everyone just throws the swim platform away and does thru-hull the easy way... lol I can't wait to get it started, now I just gotta start makin this turd faster, cause if I get passed by one more damn Baja I'm gonna scream! It's bone stock now with a SS 22P 4-blade, and tops out at 51 (lame) with 4 people and 1/2 tank. I'll start with the exhaust, and then throw an intake and carb on it to hold me over till I can actually build/stroke it. What type of props have you guys had the best luck with?

Quick question Fischan, how were you able to make the tips come straight out when the mounting surface you bolt them to was angled? Did you just grind the mounting flange ob-long so that way it would have room to be cocked at that angle???

I pulled the stock tips, which are really chrome plated brass...not stainless like I read somewhere here. Reinstall the platform without tips. From the inside of the boat, stick rolled up posterboard through the holes till it hits the inside of the ST platform. Then shoot some contrasting color spray paint down the rolled up posterboard transferring your hole to the inside of the platform.