Page 1 of 2 12 LastLast
Results 1 to 10 of 17
  1. #1
    Join Date
    Aug 2008
    Location
    Cottage Grove, MN
    Posts
    743

    Default Tips for boring out 3/4" drain thru-hull to fit a 1" thru-hull

    I currently have 1" drain lines on my rear bags but still have the 3/4 in thru-hulls. I have two questions that I'm pondering: 1) how to enlarge the hole to accept the 1" thru-hull. Since there's already a hole there, the pilot bit for a hole saw has nothing to guide it. 2) It is currently 3/4" for only 6 inches right at the fitting itself. Is this really restricting flow significantly?
    2006 Outback V - Gone
    2008 LSV - Gone
    2013 other brand

  2. #2
    Join Date
    Jan 2008
    Location
    Keuka Lake, NY
    Posts
    5,868

    Default

    its for a drain line i would not mess with it. or wake makers has a commonsize thru hull, they may work for ya.

    http://www.wakemakers.com/common-thr...itting-ss.html
    A Day at the Lake...Priceless
    A Day in Powder...Endless


    Joe V
    2012 Möbius XLV~ Loaded & Exiled
    2007 Outback V ~ sold

  3. #3
    Join Date
    Dec 2006
    Location
    Tigard, Oregon
    Posts
    3,016

    Default

    Quote Originally Posted by mnpracing View Post
    I currently have 1" drain lines on my rear bags but still have the 3/4 in thru-hulls. I have two questions that I'm pondering: 1) how to enlarge the hole to accept the 1" thru-hull. Since there's already a hole there, the pilot bit for a hole saw has nothing to guide it. 2) It is currently 3/4" for only 6 inches right at the fitting itself. Is this really restricting flow significantly?
    Mike,

    So you have a 1" drain hose that mates up to a 3/4" thru hull? I would run a simple test to see how much the difference really is. I would do this:

    1. Disconnect the hose at the thru hull and remove the thru hull. Fill the rear sac full.
    2. Drape the drain hose over the transom and reconnect the thru hull to it.
    3. Get a 5 gallon bucket or a cooler of known capacity and place it on the swim platform.
    4. Hit your empty switch and time how long it takes to fill the bucket or cooler.
    5. Refill the rear sac and remove the thru hull so your 1" hose is emptying directly into the bucket or cooler. Time how long it takes to fill.

    Make sure you keep everything the same other than the thru hull on and the thru hull off. Now extrapolate the results for the capacity of your rear sac - how much time is saved with the 1" hose vs the 3/4" thru hull? Then you can decide if the extra time is worth the time and effort to change out the thru hull with 1".

    And post your findings here!

    Al
    Last edited by cab13367; 08-15-2011 at 03:19 PM.
    Al

    2006 Mobius LSV

  4. #4
    Join Date
    Aug 2008
    Location
    Cottage Grove, MN
    Posts
    743

    Default

    Quote Originally Posted by cab13367 View Post
    Mike,

    So you have a 1" drain hose that mates up to a 3/4" thru hull? I would run a simple test to see how much the difference really is. I would do this:

    1. Disconnect the hose at the thru hull and remove the thru hull. Fill the rear sac full.
    2. Drape the drain hose over the transom and reconnect the thru hull to it.
    3. Get a 5 gallon bucket or a cooler of known capacity.
    4. Hit your empty switch and time how long it takes to fill the bucket or cooler.
    5. Refill the rear sac and remove the thru hull so your 1" hose is emptying directly into the bucket or cooler. Time how long it takes to fill.

    Now extrapolate the results for the capacity of your rear sac - how much time is saved with the 1" hose vs the 3/4" thru hull? Then you can decide if the extra time is worth the time and effort to change out the thru hull with 1".

    And post your findings here!

    Al
    Al, thanks for the idea. I'm going to try that next time out. Right now it's 1" up to the thru-hull, then I have a reducer on it to mate the hose to the thru-hull.
    2006 Outback V - Gone
    2008 LSV - Gone
    2013 other brand

  5. #5
    Join Date
    Nov 2003
    Location
    Land O Lakes, Florida
    Posts
    5,870

    Default

    I was able to just replace the 3/4 with a 1" thru hull fitting--no grinding or anything
    Hey, Its Moomba time

    13 Mobius LSV
    08 Mobius LSV-sold
    03 Mobius LSV-sold
    life is about finding the balance between being a responsible adult and staying young at heart

  6. #6
    Join Date
    Jan 2008
    Location
    Pensacola, FL
    Posts
    1,544

    Default

    You can "fill" the hole with a piece of cork. Then, start your hole with your saw and you have material to set your centerpoint. The cork grinds away easily and "perfect" center isn't needed in this case.
    1997 MasterCraft 205

    2008 Moomba Outback
    1999 MasterCraft Sportstar OB
    1992 MasterCraft 205
    1999 Malibu Response LX
    1987 Marlin Magnum Skier

  7. #7
    Join Date
    Oct 2005
    Location
    Durham, NC
    Posts
    641

    Default

    You might could try using a step drill bit, but it may not work in fiberglass. The cork sounds like good idea.
    Brian Roberts
    2001 Outback DD

  8. #8
    Join Date
    Aug 2008
    Location
    Cottage Grove, MN
    Posts
    743

    Default

    Quote Originally Posted by moombadaze View Post
    I was able to just replace the 3/4 with a 1" thru hull fitting--no grinding or anything
    haha, I guess I should try that first....
    2006 Outback V - Gone
    2008 LSV - Gone
    2013 other brand

  9. #9
    Join Date
    Jan 2008
    Location
    Tallahassee, FL
    Posts
    11,258

    Default

    Quote Originally Posted by maxpower220 View Post
    You can "fill" the hole with a piece of cork. Then, start your hole with your saw and you have material to set your centerpoint. The cork grinds away easily and "perfect" center isn't needed in this case.
    Somebody took my answer already. Lots of smart folks on here.
    My Mom said I'm not allowed to get wet!
    2008 LSV
    2000 Outback LS (sold)
    Exile Tunes
    PWI
    LLTR!!!!!!!!



  10. #10
    Join Date
    Aug 2008
    Location
    Cottage Grove, MN
    Posts
    743

    Default

    I removed the 3/4" drain thruhull from the port side, and the 1" won't fit unless I enlarge the hole. The odd (frustrating) thing is the the edges of the hole were very jagged. It took about 20 seconds with a piece of 100 grit to smooth down the gelcoat and chamfer the edges. Not sure yet whether I'll enlarge the hole. The 1" thru-hull I have is almost 1" ID, where the 3/4" stock thru-hull is barely 1/2" ID, so the difference in flow should be substantial. I'll probably test the times next time I'm out to see if it makes enough difference to me.
    2006 Outback V - Gone
    2008 LSV - Gone
    2013 other brand

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •