So I will preface this with, this was my first time tapping new holes. Additionally, I owe kudos to my neighbor, retired mechanical engineer who worked on Aircarft for Eastern Airlines and FedEx.
Take your new pedestal to the local hardware store and source the screws/bolts you wish to use, ensuring the fit properly into the base. I believe I sourced 1/4 x 1 #20 stainless bolts. (This might not even be the proper naming convention, but I know the bolts were 1/4 diameter).
Ensure your tap is of the same thread as your screws (that is fine or course).
I ended up using a 7/32nds drill bit.
Back on your boat, before you start, determine if you wish to fill in your old holes before you begin - I had some MarineTex around and filled the holes as I was also patching a spot where the Bimini rubbed on the gunnels while the prior owner was trailering the boat.
Verify in a scrap piece of wood that using the 7/32nds bit, followed by the tap (use manual force, not a drill on the tap), that your screws match the taps tread
Now on your boat, align the pedestal as you wish, and mark 1 screw location (lets say you are starting at 12 o’clock). Slowly drill into the deck, and ensure you are perpendicular to the deck (I was advised that drilling at slow/medium speed is actually more productive than drilling at high speed). The drill should easily cut through the fiberglass, and you will feel the resistance of the metal plate beneight. Here my neighbor suggested I reverse the drill and “clean the debris”, then continue drilling into the metal plate.
Once you are through the plate, its time to use the tap. Ensure the tap is properly aligned/perpendicular, and slowly thread the tap by hand. Once I started getting resistance, my neighbor suggested backing out the tap 1/4 to 1/2 a turn, and spraying some WD-40 to help lubricate the process. Continue to turn the tap until you are certain you have threaded a distance equal to the length of your screws/bolts. Back out the tap, align the pedestal, and hand tighten your first screw.
Now alight the pedestal base as you wish, and mark the location of the screw opposite of the first (so this would be 6 o’clock). Repeat drilling and taping the hole. Hand tighten this screw. Then mark the bolt at 10 o’clock, and repeat drilling/tapping. I believe at this point, I marked the balance of the bolts and then continued the process.
I was also hesitant to over torque the screws once I was done, but I tightened them as one would lug nuts in a crisscrossing pattern a few times.
Suggestion, having a shop vac around will be beneficial as you will have lots of aluminum shavings. Sadly I missed a small piece and my daughter stepped on it, exclaiming that I am not good at vacuuming (she’s 5).
I think that’s about it. If you have the tools, its probably a 30min exercise if that. Good luck!
As an aside, I should have followed my neighbor’s instructions instead of the clown at Ace who suggested I did not need a tap and a 1/4 bit would suffice. So the first hole I drilled at 12 o’clock was too large for the bolt to grab... so I had to rotate the base, and I still have a seat that is slightly misaligned! Sigh!! I learned a lesson none the less...
