Reckless, you can mount them with the actuator arms facing either in or out. The amount they open is determined by which of the three positions you mount the rod in. In the lightest position, mine are pretty much fully open by 3500rpms. In the tightest position they are open about 2/3 of the way at WOT. There is no loss of performance with either setting.

Don't expect a HUGE drop in noise though. The sight claims up to 14db. I would guess more like 2-4db. They helped a LOT at idle speeds. We went from yelling to hear each other at idle speeds to just talking a little louder than normal.

I have heard them in no wake zones and they are pretty quiet

I'm not concerned with being "very" quiet, just enough to hear the radio and satisfy the wife thru the no-wake and the neighbors after dark docking up.

If they don't open until 3500, what about backing down from 4000 to say 3000 to cruise? Will they close back up?

I think at 3000 they are still open
unless you put tighter springs in
rated at 92dba @ 3000


http://www.cpperformance.com/products/Exhaust/024.htm


I might put these in too
http://www.cpperformance.com/detail...._id=410-284401

How much they open depends on exhaust pressure. They open or close gradually depending on the rpms and which hole you mount the rods in.

I have been running Borla Mufflers outside the transom with rubber flaps, dry exhaust. I added some older style Shotguns and they are hanging in the water at idle. Does a nice job of quiet at idle. They open when power is applied and what ever is needed by the motor is what it gets. It is suppose to help mid range torque some by having some back pressure. My buddy tells me at speed I still make noise and impress the impressable, so they do what I want. In the future I plan on getting a new set, newer style, so the exhaust will be closer to being under water than it is now.
As far as legal, in mich, you cant have a switchable. Some thing that does it by itself isnt a problem yet. The silent choice is not really legal, but I think they like that quiet over nothing. Unless of course they are short of funds that month..

Good luck

Dick

Been running shotguns for years. Like Griff said, they take the "bark" out of your exhause noise. As far as being "quiet" around the marina etc... they do not do the same thing as a cutout, they do not come anywhere near the "up to 14db" the add says they can. But, in Grand Haven, I do not get a second look from the marine patrol. There are a LOT of boats with stock motors and NO muffling system that are a LOT louder. A stock 330 with straight thru hull is louder than my 400+ hp 468, even with the lumpier cam that I'm running.

Quiet at whatever level is fine with me thru the no-wakes or creeping back to the home dock after dark. But when I wanna peg the sticks I want it to scream and rattle windows. Corsa switchables run approx. $2400 for a twin set off the shelf. The shotgun series seems to be a very affordable alternative for those of us not bothered by the local FIVE-O...

Every add Ive seen states 4-9db reduction. Though his web site states up to 14db. Also according to Drew an 750hp motor only needs the guns to open 1/2 of the way....Again you can adjust the rate of opening by changing recoil springs or position of the spring in the butterfly valve lever. You also can adjust the butterfly amount of opening AT IDLE or AT SPEED.
Call Drew and talk to him he is very easy to contact and really knows his product. GREAT Warranty.

BH

4-9db I can believe!