These traditional Garboard Drain Plugs are constructed of cast bronze flanges and 1/2 inch brass plug. Garboard plugs are screw in style with #8 screw threads. Flange OD is 2 inches, pipe size is 1/2 inch. Spare plugs also available, DP1 standard square drive head and DP2 has a stainless steel pin for easy tightening.
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Drain Plugs and Tubes
What is the best material for the main boat drain plug? I see 316 Stainless, Brass and Bronze. I also see a bronze flange with brass plug.Someone said not to use stainless because the corrosive salt water would seek a soffer metal to attack. I kind of like the idea of the boat plug not corroding. Thoughts?
Softness is not really the issue below the waterline unless you are worried about impacts. This is always an interesting subject with a lot of different theories. Bronze and plastic are probably the most commonly sold, and stainless 316 should not be an issue in salt water, and is more cathodic than bronze (safer on the galvanic scale)--think of swim platform supports or other hardware at or near the waterline. Forester's Marelon garboards do not have any galvanic issues, yet still have comparable strength for underwater standards.
JD Tech Associate
Is this what I would use to connect my Porta pot to my over the water line thru hull for overboard discharge? The inside diameter of the the thru hull is 2" and is threaded. The discharge flex pipe from the Porta pot is 1 1/2".If this is not the correct fitting what should I get?
I do not believe this is what you want. This is only a 1/2" threaded plug and its the outer diameter that is 2". We recommend looking into local regulations before piecing this together, or asking your local harbormaster but generally you would want to attach a seacock or valve to the thru-hull, then plumb your porta potty to the seacock/valve. Many states mandate that the valve can be locked or zip-tied in the closed position as well when coming from an MSD. Please feel free to call one of our techs to help you find the right parts for your setup at (800) 497-0010.
JD Tech Associate
Does this have another part that attaches to the outside of the hull? & sandwiches the hull between the 2 flanges.
No it does not. It has only one flange for inside the hull.
This part is a external mount. I just applied some caulk on backside and fastened to transom with screws
The portion in the bottom of the picture is mounted to the outside of the hull, typically. It's only one flanged piece and doesn't sandwich anything.
No, there is only one part that attaches to the outside of the hull. I embedded mine in 5200 and put 5200 on the 3 screws . I cut the hole in the hull slightly larger than female threaded part so 5200 embedded that also.I have had no problems with this system
Thank you Kyle. That answered my ? Philip
what type of screw should be used for installating this below the waterline?
Seat the drain plug in epoxy and use stainless or bronze fasteners
Galvanic corrosion is a big deal with fasteners underwater. I was advised to use silicone bronze, the most similar material as the plug itself.
instruction to install on aluminum boat ?
I'm a wooden boat builder so I'm guessing a little. Rivet/bolt it in with a good treatment of 3M 5200