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  1. #1

    Default Replacing mufflers with straight pipes.

    2001 Moomba Mobius. All measurements, parts, and pictures are based on this boat. Your boat may vary. I had to split this up into several post to get all the picture in. You can see my pics at:

    http://s277.photobucket.com/albums/k...flyboy/Moomba/

    I noticed my muffler was leaking, and after looking at how poorly they are constructed, I decided to simplify the exhaust by replacing the muffler with a straight pipe. There should not be any issues with the performance of the motor. In fact, I might gain a couple of HP as the exhaust is now more free flowing. The only thing to consider is an increase in exhaust noise. For me, I like my carbon footprint to be loud! Plus, with all the music coming out of the boat, motor noise is my last concern.

    My exhaust exits the manifold and enters the muffler at 3 1/2" I.D., then exits the muffler at 3" I.D. This 3" line then continues to the exhaust exit at the back of the boat.

    Through eBay, I found Ashland Muffler House, Inc.
    http://www.ashlandmufflerhouse.com/

    For about $60: They sold me a 5' piece of 409 stainless 3" O.D. tubing. Cut it in half. Put a 30 degree bend at the end of each 30" pipe, leaving 4" of straight pipe. Here, you can see the pipes, placed next to the mufflers:



    HINDSIGHT: If I'd known that I was reducing from 3 1/2" to 3", I would have asked them if they could flange the short end to 3 1/2", saving me the headache of sleaving the small pipe to fit into the large one. I'd also have them bend the tube to 45 degrees.

    This is a picture of the pipes inserted into the large rubber exhaust:



    In this configuration, the tail of the SS pipe, overlapped the 3" rubber by 7":



    Since I'm not going back to the mufflers, I cut off 3 1/2" of this rubber exhaust to use as a sleave for fitting into the larger rubber pipe at the manifold. I used the clamps as a guide to cut. I then inserted the short end of the pipe into the sleave, giving me a perfect 3 1/2" O.D.


  2. #2

    Default Page 2

    I lubed everything up with a lot of WD40, inserted the 3" end into the 3" rubber, and then muscled the sleaved 3 1/2" end into the 3 1/2" rubber:




  3. #3

    Default Page 3

    Clamped everything down:







    I went to the boat ramp and checked for leaks. At the lower RPMs, I did not notice much more noise. The installation was clean and simple.

    Afterwards, I used the old muffler clamps to secure the exhaust. I was also careful to route and zip tie all electrical wires, hoses, or anything else that could melt well away from the SS pipe. It will be hotter than the mufflers.

  4. #4

    Default Page 4

    Addtionally, I replaced the the shaft log and repacked the gland nut. To do this, I had to remove the prop shaft flange. I simply put a socket between the flange and the transmission, tightened the bolts, and it popped loose very easily:




  5. #5

    Default Page 5

    Here's a picture of all the parts cleaned up and ready for assemble. NOTE: I was only able to use two of the packings.







    I'll let you know what the noise level is like once the winds calm down and I get on the lake. I'm really not worried about it.

    Jimmy

    KISS: Keep It Simple Stupid

  6. #6
    Join Date
    Aug 2009
    Location
    Montana
    Posts
    2,309

    Default

    definitely post up some video with the sound of that when you are done if you can
    2007 Moomba Outback - waiting for summer!

    Why Not? Play Hard! Get wet

  7. #7
    Join Date
    Sep 2009
    Location
    Grayson, Georgia
    Posts
    1,064

    Default

    This is rad.

    I can't wait to hear the sound.

    Good job sir!
    -Mark
    2005 LSV
    Tow w/:
    Volkswagen Touareg V8
    Mods: Stereo, Stainless Cup Holders and Thru Hulls, Chrome Steering Wheel, EZ Nets, Moomba Etched Cleats

    "Be more concerned with your character than your reputation, bc your character is what you really are, while your reputation is merely what others think you are."

    -John Wooden

  8. #8
    Join Date
    Jul 2002
    Location
    London Ontario Canada
    Posts
    1,856

    Default

    Excellent post and pics.......curious ...why did you replace the whole packing gland and not just the packing material, you would not have to remove the coupler and everything?

    oh and I would put some anti rust stuff on your motor mounts , they are pretty rusted.....and maybe check your alignment if you didn't>.......jmo
    09 21v LAUNCH

    run your engine after you change your oil
    68 th Member. WS420,HSE Revolution, OJ 466, Acme1157,1100 sacs,Kicker HLCD's n IX500.4, Supra Coolies
    Doug

  9. #9
    Join Date
    Nov 2010
    Location
    Katy, TX
    Posts
    4,221

    Default

    Quote Originally Posted by DOCDRS View Post

    oh and I would put some anti rust stuff on your motor mounts , they are pretty rusted.....and maybe check your alignment if you didn't>.......jmo
    i talked to the owner of a local boat repair shop today known as water junkies about the alignment. he acted like i was stupid for worrying about it. basically said "did you hit anything" and i said no, and then he said "well then why are you worried about it?"

    i could not get my engine to move to the right to close the gap so it will stay at .017.
    David

    2008 Mobius LSV, Gravity III , Wake Plate, Z5, Exile SX65c's, Exile XM9s, Exile XI12D, Exile Harpoon, Exile SM600.1 , Exile Xi800.4.

  10. #10

    Default

    Quote Originally Posted by DOCDRS View Post
    Excellent post and pics.......curious ...why did you replace the whole packing gland and not just the packing material, you would not have to remove the coupler and everything?
    I didn't replace the hardware, just cleaned it up.

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