I put a pair of mufflers on my naturally aspirated 600cu in. 750/hp motors and it wiped 15mph off my top speed ! Is the fact that these motors are N/A and need to breath the issue? I figured i'd lose a few mph but nowhere near this much. As you can figure the mufflers are coming OUT tomorrow. Anybody else have any experience with this? BTW they are Stellings dry exhaust.

Wow ,I had exactly the opposite experience. My boat goes no faster or slower with them on (5" tails on stainless marine 3's with water added right at tip as it enters the muffler),Smitty

Let me know if you are going sell them. I lost one and have been looking for some for sale. I only lost 3 mph with mine.

Did you try GGB ? 705-382-5275

I had no loss or gain with mine on a 600 CU IN EFI N/A. I love them. Running CMI's on the engines.

Who's motors do you have.

I have GGB extremes on my NA 540, 680 hp, running full dry CMI's. I noticed no speed loss at all. Unfortunetly, as far as I know, GGB is out of business.

GGB in NOT out of business, I posted the number above.

I am running 750 Cobras through Stellings dry exhaust.

ME,ME,ME.

Seriously, I put the mufflers on f311fr1's boat and was really impressed. The boat lost NO speed and they cut the noise in half. Would not hesitate to use them again.

Have people had good success using the CMI sound elimination system mufflers? I'm about to put a set on my boat.