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Old 04-02-2012, 05:25 PM   #1
Join Date: Aug 2011
Posts: 511
Underwater exhaust??

Anyone here running the Centek version? I have a T6.354 Perkins in my 34 Mainship and it has NO muffler at all on the main. My exhaust run is pretty level as the P.O. replaced the elbow and it doesn't have much of a rise to it. I don't really care for that and was thinking about a waterlift and during my research saw the underwater systems. Will the backpressure of a waterlift muffler affect my turbo? I don't run it above 1800 for any length of time. In fact today was one of those pristine days with slick water and virtually 0 tide so I could play around and found that +/- 1300 RPM would put me between 6.5-7 kts. This truly seems to be the boat's sweet spot. (vibrations, responsive helm, enough forward momentum to smooth small waves, etc). But I'd really like to quieten the exhaust note.

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Old 04-02-2012, 05:52 PM   #2
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Don't know about underwater exhaust but my previous boat also had no muffler and it was loud, both on the boat and outside (my neighbors called the boat "the Cessna" because it was obnoxiously loud). The exhaust line had a good slope to it (engine had a fairly high exhaust riser) so I put in a Centek inline muffler and it certainly made boating life more comfortable for everyone on and off. It was a cheaper and easier fix than a waterlift- style solution.

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Old 04-02-2012, 05:59 PM   #3
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the lack of a nice slope in the exhaust plumbing is why I was considering the waterlift. A taller elbow and a inline muffler would probably be a good alternative but I REALLY like how quiet my genset is outside the boat. Its noisier inside (its the original CrossPower MD5 Volvo one lung vibrator).
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Old 04-07-2012, 06:17 AM   #4
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Water lift mufflers are great. On our 90/90 the exhaust sounds like someone reliving himself from the deck.

BE advised that on a larger engine not all the sea water cooling can be discharged thru a lift muffler, si a bypass is required.

Also on a long cranking engine no start situation , the lift could fill with water and flood the engine. Securing the sea cock is required.

Finally the lift muffler will require a drain plug so it can be winterized.

The PIA of all these minor points is nothing compared to the SOUND OF SILENCE , while operating.

A properly sized unit is needed for the best results.

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Old 04-07-2012, 06:55 AM   #5
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Originally Posted by FF View Post
Finally the lift muffler will require a drain plug so it can be winterized.
I live just down river from you!! If I have to winterize, I'm moving again!
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Old 04-07-2012, 03:24 PM   #6
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I have Centek water-lift mufflers on my twin 160hp turbocharged Yanmars. The exhaust sound is audible but not at all intrusive, even at WOT. I am more comfortable with my exhausts discharging above the water line - one less thing to worry about. My first check on starting engines and generator is a quick trip to the stern rail to listen for that reassuring burble-burble-whooosh sound of water coming out along with the exhaust. Seems to me that this check would not be possible with underwater exhausts.
If all else fails, read the instructions
If it ain't broke, don't fix it
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Old 04-07-2012, 11:34 PM   #7
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Look up and read this series of articles about marine exhausts. Look through them well before you start changing. If you recognize some of the problems talked about you may save yourself an expensive repair and while modifying what you have incorporate some improvements.
From your original note it sounds like you might have a potential backflow to the engine or the elbow.

Seaboard Marine - Tony's Tips

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