Jassman

Building a New Nortech 4300 I'm tired of having problems with switchables. What is the best muffler out there for 875-1150 hp, with out hp loss if possible. Thanks Jeff

Brad Zastrow

I feel your pain on this issue. I have been using Livorsi's switchables with good sucess at idle speed only. Dyno was 1000hp. I found I could not run them on over idle. Way too much back pressure and even cruising speeds it would blow the flaps clean off. The mufflers have kept me out of trouble with the noise police at idle, however they would not pass the db test. Ithink they see that I am trying to keep it down with the big mufflers. However at speed this boat is real loud. Rumor is CMI is coming out with an internal tail pipe muffler for the big guns. This is a big issue for me as well. Certain areas are getting real tough on the noise.

Lofty

Jassman, I have been talking to GGB about some big-gun cans that won't kill the upper end. With 6" transom mount AND and an in-line they can keep you 15db's under where you are with nothing. They are seeing a 50rpm loss at WOT.

Brad Zastrow

I just spoke to Randy from CMI in Wisconsin. Thay are testing some internal mufflers on some 1100hp engines. He asked me to check back in a few weeks. I am guessing Mercury may be involved somehow needing mufflers for the 1075's. Many states require DB limits on new boats and even existing boats. I think this noise issue is going to get much worse for us.

John B

I put HPI internals (full time & wet) on two 900+ hp Sterlings that are in a 36 Skater and they cut the high speed noise way down. At idle (1100) they are about 98 db but it is a low deep sound which is not annoying. If the idle speed is lower, like 800, the noise is about 94 db, all J2004 readings. Technically still too high but it sounds lower because it's only the low frequencies.

I assume there is some power loss, maybe 20-40 hp. Since it runs over 140 who cares if I lost 2 mph?

Kilo cat uses HPI's, maybe he can also attest to his results. He told me they worked for him as well.

Regards, John B