Loud at Idle and slow cruise, Cummins 370

[forenic]

I have a 1990 32 sportfish w/ 370 Cummins. Exhaust is very loud at Idle and slow cruise (Before turbo kicks in). Once turbo kicks in it quiets out. Wondering what other people have in there boats? Looks like engine was upgraded to 370hp in 1997. Don't remember seeing muffler. Configuration 6" hose off engine and 2 90 elbows to transom. Doesn't have a lot vertical clearance to play with. I don't mind running fast, but I have some slow speed zones I go thru that the sound is overwhelming. This was my first season with boat, still catching up on fixing all the neglected things from previous owner.

[BarryG]

Well, if there is no muffler between the turbo and the transom, it seems to me that would explain the loud exhaust. I have a 2002 with 370, but it has a rather large muffler just before it exits out the transom. The loudness is subjective as well...

[leelambert]

Forenic, Tony@sbmar.com may have some insight if you were to email some pictures and description. I found that Tony has a lot of experience with Cummins marine exhaust systems.

[forenic]

Will do, have been try to get launched before dealing with it, Will post some picture when I start getting into it. Exhaust is 6" w/ 2-90° and small inline muffler. Have a bunch of old impeller blades in my HX that I need to remove to increase water flow (next project), this might help. Also going to try and scope muffler before I launch to check baffles. Only loud in low rpm range, once turbo kicks in quiets out!

Thanks for all the replies!

Cliff Dean
32 SF