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08-15-2011, 01:30 PM #1Senior Member
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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
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08-15-2011, 01:53 PM #2
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.htmlA Day at the Lake...Priceless
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Joe V
2012 Möbius XLV~ Loaded & Exiled
2007 Outback V ~ sold
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08-15-2011, 03:05 PM #3
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!
AlLast edited by cab13367; 08-15-2011 at 03:19 PM.
Al
2006 Mobius LSV
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08-15-2011, 03:27 PM #4Senior Member
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08-15-2011, 07:12 PM #5
I was able to just replace the 3/4 with a 1" thru hull fitting--no grinding or anything
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08-15-2011, 09:58 PM #6Senior Member
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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.
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08-15-2011, 10:13 PM #7Banned
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You might could try using a step drill bit, but it may not work in fiberglass. The cork sounds like good idea.
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08-15-2011, 11:04 PM #8Senior Member
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08-16-2011, 01:18 PM #9
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08-18-2011, 10:03 AM #10Senior Member
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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