How loud are the Gil thur transom tips ? they are the factory installed ones with the auger inside and do they hurt the performance and will they pass the sound test ?

I ran those for several years. They reduce the bark a great deal. You can talk over them at idle and on plane. When I changed them out I picked up 150 RPM on a 502. I think they do kill top end somewhat. Best to go to a switchable if you are making a good deal of power.

http://www.hpisilencers.com/

I'm running modified 420s dyno'd 505 hp. The boat only had the exhaust run thur the lower units before, so this should help I just don't need to deal with to much noise around the Marina.... don't like tickets !!!