Hey eveybody! i bought a 1991 357 sr1 middle of summer. was a Pennsylvania boat i picked it up in baltimore. had 502's and bravo 1,s. i gutted the interior, pulled both motors and drives and have got into a BIG ORDEAL. bith transom assy bad replaced them both brand new. motors are almost done. went with 6-625HP roller 509's . drives are being built now to hold up to 750hp. i am so excited this build should be BAD ASS! gel coat and outside like new! some guy that owned the boat in PA had everything rigged hal assed. 1 gill dry riser then other side had shorter merc dry riser, 1 motor was 2011 merc 502 other was built 509. everything i have touched needed replaced. has hardine marine tube manifolds wich are pretty cool but require wedges wich suck! i put all kicker and alpine sound system(4000.00). looks like about 27-30k in build. i paid 19k. oh and a nextrail allum i beam trailer. i am fired up to get it in the water in the spring!! i was thinking of removing the silent thunder, i bought 12inch spiral muffler tips, my only concern is buying a swim platform that will fit the same holes as the silent thunder. all the gauges are hardine and look great. any ideas would be much appreciated. Fever marine(Tom Shlentz) is doing all the work. 45-60 days it will be done!!!!!!!!

Don't remove the silent thunder swim platform, just cut the bottoms out of the exhaust chambers. I did that on a 1990 292 SR1 and it worked out great. cutting the bottoms out let exhaust out, cool loud sound and it did not adversly effect the structural integrity of the platform. Also, keep that sleeper look of a stock formula. Post pics please!!!!!

I say ditch the silent thunder and find a custom aluminum fabricator if funds are available they will e able to get mounting to work. I hate silent thunder. Took mine off and putting a teak one on. Don't have money for an aluminum pls already dropping a fortune on te boat. I've always liked te look of teak platforms on classic sportboats.

Check out this place..I bought a 1987 F-311 SR-1 with twin 420 and TRS and am going through some of the same pains you are..half assed maintenance by previous owner and came to find out the port engine had 2 cracked heads..a whole summer of frustration chasing ghosts but I am tearing her down this winter and will have her running for next summer..pretty will come later..speed is first and foremost..but I got a good deal even with the problems like you did! I am planning on ditching the Silent Thunder as well and in my research I found and like this platform..you will most likely have to fill old holes and drill new ones with whatever platform you put on..
good luck and post some before and after pics..or better yet well get the birds together at PIB this summer and swap war stories over a few cold ones!
http://www.alummetalfab.com/

Leave the silent thunder on. If your running large engines with a good exhaust you will be happy you did. Do as 38fountain suggests, cut holes in the bottom of the platform. I took a 4" hole saw and cut a hole in each chamber in my 292. I'm running gill exhausts with dry to the tip pipes and at idle it can be a bit loud if I'm trying to talk to people sitting in the back bench. With the platform off the engines are way to loud, yes it sounds cool, but its to loud. Loud is only fun for a while, eventually you'll get sick it.

i think i will try the cut theory this year. can u go bigger with the hoes, like 8 inch????

You can always go bigger withe the "hoes"

I agree on leaving factory platform, makes the look on them boats, tubular does not flow well on the Formula in my opinion... you can make the factory one sound good, remove it, cut baffles out, and hole saw holes all over under the platform... sounds sweet!

HOLES splitdecision!!! lol thats what i will do cut outs and remove baffles. i am so ready to hear those 509's rumble!!!!

Do you need to put flappers on the pipes if you cut out baffles and holes in the platform? I havent had mine off and not sure whats in there..I may go this route for this season as well..but my platform has some spidercracking in it from PO not being a good captain!