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Thread: Through transom exhaust

  1. #1
    Speedin' Ian
    I am interested in putting through transom exhaust on my boat, it has a merc 260 with an Alpha 1 outdrive. I know I will have to remove the motor to get ride of the y-pipe, but what else is involved. I am worried about cutting the holes in the boat . Has anyone else done this, can you lend me any advice.

  2. #2
    Jordy
    Not to lend a negative view, but I'm just wondering what you're trying to accomplish. Are you looking for more performance, better sound, something to do? Are you planning on changing out the stock risers and manifolds or are you going to leave them stock and just go out the transom? The reason I'm asking is just to see if you have considered the amount of work that is involved and taken into consideration the gains you'll see after it's done.

  3. #3
    Havasu Hangin'
    I did mine. Before you pull the engine, mockup where the exhaust will exit the transom (I used L-pipes and hose from Eddie- sorry Rex), and ran mine under the swimsteps- this is kinda important to make sure there is nothing blocking the route (pump, blower, etc.).
    After I pulled the engine, I unbolted the Y-pipe, and made a block-off plate. Then I drilled a pilot hole from where I mocked up where the tips will go (the center of the tip cutout). Measure a 4" circle around the pilot hole (on both sides) to make sure they are in the right location (and even). Then, measure another inch, as that how much room the flange will need.
    At this point, if the pilot hole is off, you can re-drill it, as it will be part of the material removed anyway (unless you are 2" or more off!)
    Put masking tape on the transom to keep the gel safe. Use a 4" holesaw and take your time. After your done, grind out a little (1/8" or so), and put some resin on the exposed wood.
    After the resin dries, insert the tips (I got mine from Eddie Marine-sorry Rex). Mark the holes...remove the tips and drill the holes. Remove the masking tape.
    Silicone the flange, and re-insert it. Screw the tips in.
    After you install the engine, put the hoses and clamps on loosely (I use double clamps from Eddie Marine- sorry Rex). Just make sure there is no binding and tighten the clamps up.
    All in all, it looks tough...but is one of the easier jobs. Measure twice...or three times (if you make a mistake with the hole saw...it'll cost you $800 bucks or so to replace the wood), and use the hole saw once.
    PS- don't listen to Jordy...he's a "half-empty" kinda guy (who is still reaping the full performance benefits of a velocity stack).

  4. #4
    Kim Hanson
    Why would you do this though? To make the exhaust quite, get rid of the headers hanging out the back?
    Jordy fish bowls works HH, I seen pictures .........( . )( . )......

  5. #5
    Speedin' Ian
    I'm doing it strictly for the sound and do not expect any performance gaains. I plan on using the stock manifolds and picking up some elbows and tips from Rex Marine.

  6. #6
    Mandelon
    And when you're done you'll have a boat that probably won't pass the new exhaust law like the rest of us.
    I read somewhere you could pick up 3 to 5 mph with through hull exhaust....

  7. #7
    Havasu Hangin'
    Originally posted by Kim Hanson
    Why would you do this though? To make the exhaust quite, get rid of the headers hanging out the back?
    Kim- the Merc setups run the exhaust through the hub of the prop. By getting away from that...you let the engine breathe a little more (like you outbored guys do).
    It also keeps the hot exhaust from going out the outdrive.
    Originally posted by Kim Hanson
    Jordy fish bowls works HH, I seen pictures..
    Well...I guess we can't argue with that 5 MPH he pick up when he put the velocity stack on!
    Originally posted by Mandelon
    And when you're done you'll have a boat that probably won't pass the new exhaust law like the rest of us.
    Actually...off plane...my boat just makes bubbles.

  8. #8
    Kim Hanson
    Originally posted by Mandelon
    And when you're done you'll have a boat that probably won't pass the new exhaust law like the rest of us.
    I read somewhere you could pick up 3 to 5 mph with through hull exhaust....
    I run SuperTrapps on my V-Drive, it's still loud! I think I will be able to use it though..........( . )( . )........
    I read somewhere you could pick up 3 to 5 mph with through hull exhaust...In your dreams..BBbWWWWwHHhaaaaaaaaaa

  9. #9
    LASERRAY
    Originally posted by Mandelon
    I read somewhere you could pick up 3 to 5 mph with through hull exhaust.... Our "brother in smack" Kilrtoy will never live that down! J/K Kil.

  10. #10
    Havasu Hangin'
    Originally posted by Kim Hanson
    I run SuperTrapps on my V-Drive, it's still loud! I think I will be able to use it though...
    My stereo is actually louder than my exhaust...what a screwed up boat.

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