I searched the Forum with no luck- 311 SR1 with the ST platform. Want to do the mod on the bottom and want to know if anyone has pictures- I have seen this done with 4" (or 6"?) inspection plate trim rings around the holes. What did you use to do the cut outs and was it a btch? Pointers appreciated- it is almost spring and I am going nuts.

I wouldn't drill any holes in the platform. It was done to my 311 and the sound of the exhaust suffered, had a vibration. If it was me I would make make hoses that bipassed the box. I belive rambunctious did this on his 272.

Here is the link
http://www.offshoreonly.com/forums/s...silent+thunder

Vely intellesting . . . the vibration was generated by the holes in the box? That is not a good thing.

Yeah the vibration was caused by the holes. It was very noticable around 1100 rpm it almost hurt the ears. Over 2000rpm it was not noticable. One day I took a few rubber plugs and sealed all the holes. The vibration went away.

Hope this helps
Don

My 311 has the optional cutouts in the bottom side of the ST platform, courtesy of the previous owner. There is four of them, about six by six inches. It is noticably louder than the stock platform and I didn't like the noise at first. I was going to cover them up but my wife actually liked it and I got used to it.

There is a rattle back there somewhere but I always thought it was the swim ladder. I've seen other boats with a bungee cord wrapped around the ladder so maybe that would solve it.

I used a wood spade to cut two 1 1/2" holes in each of my baffles. Then I opened up the platform and doubles the outlets, one stacked on top of the other. Lowered the water level in the platform and it sounded great. I will see if I can find pics.

I have the same "modification" in my board from a previous owner. Thankfully, that guy cut 4" holes and installed deck plates in them so they can be opened or closed. Ran the boat with them open for a while but, like you said Duck, the vibration at slow speeds was nasty. It was especially bad at idle speeds. So, the deck plates are closed.

Want to get rid of the vibration sounds???

Take the damned thing off....