Silent Thunder exhaust flaps
 

One of my exhaust manifolds went bad last weekend and upon removing the Gil tailpipes, I see that there are no flaps on the tips that go through the transom into the swim platform. Is this normal? There is a bar that runs vertically about the size of a pencil in the middle of the tips. Does anyone know where I can get some Merc/ Gil manifolds?

Thanks, Craig

Never having my Silent Thunder platform off, I don't think there's any internal flappers. Only the ones at the end of the platform.
Can't see why you'd need them on inside, the baffles should stop any water from backwashing.

Craig,
My 223LS does have flappers in the tailpipes. They were both half gone, so I replaced them with the Merc parts, which was a mistake. Something like $100 for two. I saw them in the Cp Performance catalog for about $40. Looked identical. If you do replace them make sure you put some sort of silcon on the top and bottom, or they will rattle. The keepers are rivited to the inside of the tailpipes. Mine looked okay, so I didn't replace them.

Scott

thanks guys,
Check this out. The cheapest that I could find replacement Gil/Mercruiser manifolds was $1375 per side. I called Gil Marine directly and they charge $1175 per PAIR. Same manifold but it doesn't say Mercruiser on the side. WTF!! Can you guess which ones I ordered:D :D :D

Craig, I had a baffle come loose on my 272 last week. when I pulled it out. I saw exactly what you did. thru hulls with a narrow piece vertically down the center. no flaps. I assume this is ok as my previous boat (211 liberator) had thru hulls with no flappers or no baffles at all???

the baffles in my silent thunder are about 10" away from the transom. only one baffle (vertical wall with 1" gap at bottom) each chamber.

when they are removed. only the swim platform keeps waves from entering the exhaust. but i think just the slope of the exhaust pipe is what trully keeps the water out because I think many have open exhaust.(other boat makes)

Not to get to far off the subject but do any of you have a exhaust leak between the transome and the silent thunder? If so what did you do to fix.

Russ

Russ see your Private message

My Silent Thunder platform also leaks. I think it needs a new gasket. That's going to have to wait until winter:D :D
Did you guys cut out the baffle from the inside or drill holes?
How much louder is it? My boat is pretty loud on plane but is way too quiet at idle.

I'm still waiting for my new Gil manifolds. They are supposed to be here today. It's hard to believe that they don't make a bunch of them in the winter to establish some excess stock:mad:


Thanks, Craig

I only have one port that does not have the baffle now. it is louder, but only one engine bank. I was going to drill two 2" holes each, but seing how simple the baffle is I will cut them out when I remove the platform.

heck. maybe I will drill them out this week, then do the rest when I remove the platform... yea... gotta go get a long drill :D

Rambunctious,
clean out your e-mail box

Russ

Mine have been drilled for about 2+ years now. One 2" hole and one 1.5" hole in each baffle. Nice rumble but not too too loud.:)

Trevor

Baffles in Silent Thunder
 

I took the baffle 1 step furthur,

I put a 540 in a 242ls. This really made the Formula come alive.
I drilled out the baffles with a 2" hole saw, the i drilled 2 holes in the radiused are under the platform almost where the thru-hull comes through the transom. I installed 3"rubber flappers over the holes. IT sounds nice now! The rubber prevents backwash of water comming into the platform. The beauty of this is that you can not see the additional holes when the boat is standing still. My next step will be to install tips through the hole.

Anybody who wants the details on this conversion, I will be happy to have a discussion.

Sheikman

Hey Craig, I'm on my third Formula now. Its a 311. Had the platform off my 242 and my 311 because of exhaust leaks. There are two different sets of gaskets in there. One set is a round foam deal that seals the exhaust tip to the backside of the platform. the other is a peripheral gasket that goes all around the outside edge of the board. The round ones at the tips are the ones that seal the exhaust. Taking the platform off is not too hard but its pretty heavy, need two guys for sure. When its off, check for delamination between the fiberglass face on the back of the platform and the oak backing board. If it is delaminated a bit, get some acatone and rinse the space a bit. Then inject as much 3M 5000 adhesive in there as you can. Clamp it and let it cure real well. This needs to be done or it will get worse and worse. The round gaskets have no adhesive on them. Spread a little contact cement on both the gasket and the platform to keep it in place while installing the platform. The long peripheral gasket is pre-glued. Hope this helps you visualize whats in store for you. Like I said, I've done it twice (basically rebuilt my 311 platform) so let me know if you need any more info.

As far as modifying baffles and louder sound, see my new psot on special tool for silent thunder baffes:D :D :D