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

[cab13367]

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