Bolts for attaching silent thunder exhaust( 1992 and newer)
 

Help... I am missing these two mounting bolts for my silent thunder exhaust. This is causing the silent thunder box to vibrate and make a fair amount of noise. Does anyone know the dimension of these bolts? Locations are where small arrows are shown.

Just received an email from Lakeport Landing... Jean there is great:

Bolts are 3/8" x 1 3/4" corse thread (16) stainless bolts
3/8" lock washers
3/8 flat washers

installed the two bolts today and the boat still has a rattle in the exhaust. How have others dealt with this?

You may have a baffle loose in the box or the box is cracked, may have to take it off to inspect

I was afraid of that.

I pulled mine off last fall because it rattled and I had exhaust leaks around it with some soot on the transom. It turned out to be cracked in a few different places. I'm going to leave it off, but I'll try to fix it this summer in case I get hassled for noise.

Some of the rattling noise might be the flappers popping open and closed when it's idleing too.

Bill-
It is definitely rattling in the silent thunder box. I just bought the boat this winter and found the two bolts missing. Not sure how long they have been gone. Think that I will remove the silent thunder box and check things over. I want to keep the box for sound reduction if possible otherwise I will remove and add round flappers to exhaust tips.

Dave

Tried to tighten the two outside bolts and now one won't hold edge down tight. Looks like the box will be coming off next week.

Bill - Do you know the dimension of the exhaust tip that is mounted on the transom?When I pull the box off I want to have two tips ready to use in case the box is DOA and will be a while to repair. My guess is that they are 3 1/2" or 4" flappers.

Thanks

They are 4", and you'll need 4 of them.

When I took mine off, I removed the 2 bolts and the two nuts from the swim ladder. At that point the platform really didn't drop much, maybe a half inch on one side is all. I removed the screws from the bottom transom brackets and kind of pulled down on the back edge and it still wouldn't come free. I tied some clothesline through the bolt holes and secured it to the cleats up top to keep it from falling (did this job myself and wasn't sure how heavy it would be.) Then I grabbed the edge at the transom and pulled back and that freed it. The holes in the platform fit over the tips and the gaskets held it on too.

Just a little advice so you're not standing there scratching your head wondering why it's not coming off.