I was looking to get some of these but wondering if they will quiet it down much. Stock 525s with dry tails.

http://www.offshoreonly.com/forums/g...b-inserts.html

Also they are mentioned a number of other times.
http://www.offshoreonly.com/forums/s...archid=2204447

I used a set on an 900 HP blower engine with CMI's and dry tails. They made a big difference in sound. Didn't cost much HP on the dyno either.

Thanks. I appreciate any info.

I use GGB inserts but in wet thru hull so I can only give you partial information. I get about a 6-8dB reduction in a SBC application with 4" thru-hull. The motor sounds much better (appealing to me) with them in compared to open exhaust or even compared to other inserts I've tried. These did not reduce my WOT rpm at all.

I've tried some CP Performance inserts and they choked about 500 rpm at WOT, reduced the dB the same and didn't sound as good as the GGBs.

The design appears to work in concert with water (wet) pipes so I'd estimate your sound suppression would be much less in your dry setup.

I also run them on wet exhaust and they work quite well for that. They do reduce the noise when dry, but not much. I haven't measured them before the water hits on dry startup (to compare to the pre-insert values), but likely a db or two. Then when the water hots them i see a big drop and the tone changes greatly. I measured 8 db drop @ 1m when wet.