Thought everyone may find this interesting. I had emailed GGB several weeks ago and they just sent me this reply to my question below.
Here's the question... Can you quiet this boat down with the existing headers, keep the performance and meet the 88dba @ 5 feet? The Howard Runner Bottom sports a 468 BBC with a 6-71 blower and Rewarder V-Drive Headers... Thanks, Jeff.
http://www.***boat.com/image_center/...110005-med.JPG
Jeff,
We just finished testing with our new OT muffler. Test boat run a set-up simalar to yours. 468 chev with blower. (the actual boat is online in our boat pics link of site - Owner is Rick sisson). With engine idle at 800 rpm, no water in the headers, 5' from the boat, it came in at 88dB.
I have a couple other guy's running them and feedback so far on performance is very little if any loss on top end.
Click on the link below and then go to OT mufflers...
http://www.ggb.ca/index2.html