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Silent Thunder Removal


Silent Thunder Removal

Old 07-01-2020, 12:29 PM
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Default Silent Thunder Removal

I wanted to share a start to finish post about removing the Silent Thunder and installing exhaust tips with photos and DB readings.

I have a 94 SR1 336 w/ 502 Mags, no silent choice.

I started by removing the 4 nuts/bolts at the rear of the Silent thunder box and the 2 through bolts at the forward center area.
I used a few pry bars/cats paws to slip in between the rear of the box and the bottom edge of the swim platform.
Mine appeared to be glued on from the factory. Once I got the port corner started I would slide and gently pry down until I could slide the pry bar a little bit to the starboard side and so on and so on.

My neighbor was kind enough to help me on this at thank god because once the box is lose it drops right down.
The box weighed well over 100 lbs. and the foam that is used on the underside was completely saturated with water.
Once removed the stock exhaust tips are exposed. I could have just put rubber flaps on the end of these but I preferred the look of the Corsa Exhaust tips/mufflers. Plus I got what I think is a smoking deal on them. All 4 for $175.

Each of the stock tips are secured by 3 lag screws from the outside and 2 clamps on the inside from the exhaust hose to the tip. The stock tips were also silicone to the transom. In order to easily remove the stock tips I used a rubber mallet and plastic wedge/shims I had laying around. They worked great and break the silicone lose and allowing me to pry the tips out of the exhaust hose w/o causing any damage to the gel coat on the transom.

Next I made a template of the mounting face of the Corsa Tips out of 1/4 plywood in order to mark where I needed to drill holes to slide the studs through the transom. Unfortunately the stock lag screws holes do not line up to the studs for the Corsa Tips. I did not have to change the stock opening of the exhaust hole in the transom at all.

The next step may not be needed but I felt it made installing the lock nuts onto the studs of the tips easier, I removed the risers and exhaust hose from the manifolds. The exhaust hose does not have much play in them so this is why I just unbolted the risers from the manifold and kept the hose attached to the riser. I did replace each of the gaskets from the riser to the manifold, they were about $12 each.

Prior to sliding the new tips through the transom I put a thick bead of 4200 caulk on the mounting face of each of the tips. I installed the lock nuts on the studs and snugged them up until I had a nice fit from the mounting face of the Corsa tips to the transom. Then I cleaned up any excess caulk.

Finally I added the rubber flaps on the outside. I don’t believe this is needed as the tips come with the backflow flaps installed but I did it as I thought it is a cleaner look and for extra measures.

The stock DB's at idle:
Max 104, Average 102.5

Corsa Tips DB's at idle
Max 103, Average 101.5

All readings were done while the boat was in the water.

I did not check DB's while running as it was not that important to me and with wind noise I did not feel there would be an accurate reading.

There is definitely a difference in sound. The Corsa Tips produce a throatier rumble throughout all RPM's.

I have not seen/checked if I gained any performance /rpms/ or speed. Maybe I will gain a mph from the weight reduction but I made the change for looks and the stock rubber flaps on the box kept tearing on me and I was tired of replacing them.

Hope this helps anyone who is looking to complete the project.


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teebee9320 (08-04-2020)
Old 07-01-2020, 01:45 PM
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Wow looks like you did a awesome job.
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Old 07-18-2020, 09:51 AM
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Would love to see the profile of the boat with the platform but without the silent Thunder underneath it.
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Old 08-04-2020, 09:41 AM
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Do you have DB readings with the silent thunder still installed by any chance?
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