47' Commander Original Cast Iron Exhaust Mufflers ???

47 Commander 1973 Muffler Replacement

Warren Whitmore

January, 2024

Regarding mufflers, my 1973 47 had the 6" fiberglass Venatones from the factory. I'm not sure how it actually sounded as I bought it as a project on the hard. When I removed the Cummins VT8-370Ms and installed Caterpillar 3208TAs I added Vetus waterlift mufflers inline between the turbos and the Vernatones. I was able to mount them behind the engines above the shafts. At the transom with the engines running you can't hear the exhaust over the engine mechanical noise coming back from the engine room vents.

From the Archives - 2009 - 2011

I installed mufflers in my 47’ CC when I repowered it, (Cummins 6BTA 370’s). I used the vertical round can type with the inlet on the side and the exhaust on the top. At idle there is virtually no noise coming out of the exhaust tips at the stern. They are installed in the engine room before the fiberglass exhaust tube goes through the bulkhead.

They were from Vernalift and are fiberglass painted black. I repainted them white and still look good after almost 500 hours. I have a lot of room because of my straight 6 cylinders. Not sure if this would work with you V8’s.

Rob

47’ CC 1972 Fascination

#32336 From: bccheston@...Date: Sat Mar 21, 2009 11:56 amSubject: 47 mufflers

The cast iron mufflers were between the hull and the fuel tanks in the aft state roomThe reason I moved them was that they did not fit. The cast irom were 8" wide and theVernatone are 12" wide and the same length. Getting the CI out I used a winch. They areheavy, once you have them on top of the tanks (plywood) It takes two with many a gruntto get them out of the boat. Check the exhaust hoses to see if they are rubbing anywhere.The one on the port side is close to the bulkhead between the aft state room and the Mid SRand may be rubbing or have a hole in it. I suggest you call your marine supplier the hoseID is 8". and they may have o order the VERNATONEs they are quite and sound great.Constantine

#43148 From: "Rob Dengler" <rdengler@...>Date: Tue Dec 13, 2011 8:26 amSubject: RE: [CCCC] 1969 47fft "loud"

Attached you will find two photos of my mufflers on my main engines. The first photo is the star side and the darker one is the port. My florescent lighting don’t like the cold, sorry a little dark. On top of both mufflers I have a riser to keep water from coming back up through the exhaust. During storms I can get large waves on my stern in the slip. Several people in my marina have destroyed engines when they are packed full of water during a bad storm from extreme wave action and then start them.

I run 5 gallons of the -0110 antifreeze through each engine so I don’t need to drain the muffles. That is such a mess and it takes for every for it to drain all out.Hope this helps.Rob Dengler1972 47’ Fascination 

From Jim Wick 2002: Centek, should have mufflers that should work. If you can have 9" in width

rather than the 6" you now have, it is a piece of cake. Shape is about

the same. Length, 42.5".

It may not be one of their on the shelf items, but they can make them..

Your cast iron mufflers have baffels (or had) that extend down into the

box. Sound of the FG mufflers is very much the same as the CC cast iron.

11851

From: froggy3k47  <froggy3k@h...>

Date: Mon Apr 14, 2003 11:47am

Subject: Re: mufflers-Long Reply

  Paul Asked:  Hello Fellow Commanders'

I am in need of mufflers for my 1969 47' Commander. It is powered

with

DD8V53's. Does any body know where to get NOS cast iron units? Has

anyone

replaced their's with something different?

Paul,

I asked this question a bit back also.  You are not alone as a few

other CCCC members are looking at the same dilemma.  We have a 69 47'

with the same motors.  Tim sent me this response (Tim, I hope you

don't mind me quoting you.  Your information was most helpful):

<<<<<

I have a 69 47' with 8V53's. I replaced my entire exhaust system with

fiberglass pipes and mufflers. I had Primex (Marine Muffler Corp)

fabricate custom mufflers for me from there standard shells. They

were most helpful in the design of the custom units. I installed them

just forward of where the original units were. There is not much of a

noticeable sound change from the glass units over the cast iron units

with the exception of that famous Chris Craft load and unload sound

that the top fill cast iron mufflers produced (that's the  bad). I

measured the back pressure from the new fiberglass units and found it

to be lower then the cast iron mufflers. The hardest part of the

whole

project was the removal of the original cast iron units (that's the

ugly). The project actually removes literally several hundred pounds

of

weight from the boat (that's the good) >>>>>>>

The mufflers Tim used were Marine Muffler Brand part number NPNMC-060-

1221.  These are 6" inlet and outlet, 41 1/2" overall length, 29 1/2"

body length and 10" in diameter.  20% reduction in sound vs. straight

pipe (as per David-MMC employee)  Approx 2 week lead time to build.

These were original equipment on the Carolina Classics.  It appears

this is what I will be using.  Centek does make something similar but

a shorter body length. (These are called 'Mini Max').

It appears after the original cast items are removed (with modifying

the aft cabin for removal-careful, these are HEAVY!), these will fit

just forward of where the original units were.  I'm planning on

having the outlet of the muffler 'rest' on the forward mount of the

original supports.  Then dropping the wooden 'rest' that the original

rubber exhaust hoses were sitting on by 2" (10" diameter vs. +6" of

the old hose).  In theory (??) this should make everything align

correctly. One support just in front of the old muffler supports will

need to be notched downward by 2".  It appears a 10" shell will

fit

with +1" on each side.  Also, the wooden bulkhead for the 3rd

cabin and head

has to be notched out so you can get to the clamps on the inlet

side.  This bulkhead is just space as there aren't any brackets

or

anything in this area.

I replaced my entire exhaust last year with hose and fiberglass

tubing due to being worried about the mufflers rotting out and

sinking the boat (which I've heard happening).  The mufflers did show

signs of premature failure by external rust on the bottom of the

units.  The original rubber

exhaust had cracks about 4 plies deep on each side the entire length

of hose.  It was only a matter of time before it ruptured.  Ran out

of time (and $) so I didn't replace the mufflers then.  Well, let me

tell you, they will be replaced before splashing this spring.

Awfully loud!!!!  I did replace the check valves with MMC units last

year (non resonator type).  These I mounted just inside the transom

so I could check the flappers from outside by sticking my arm in the

exhaust vs. pulling out the shower stall and breaking the exhaust

connections.  Ok other than hearing `clicking' while at

anchor with

waves entering and exiting the exhaust tubes.  Hearing the stereo

clicking assures me that the flaps are still intact and working.

I've gotten used to it.

Maybe all of us that need these mufflers can get together and get

a `group' price?

Chris Grubb

'69 47' Commander

FAE-47-0013F

Mark,

If you remove a cast iron muffler and do up a reasonably detailed sketch for Centek, they can determine if one of their existing designs fit or they can make you custom mufflers out of fiberglass as "drop in" replacements for the original cast iron versions. Note that Marine Muffler Corp as mentioned in the 2003 post Charlene Pike attached is no longer in business. However, beyond Centek there is also Soundown and other custom muffler manufacturers that can be found via Google.