Water Inlet/Regulator Replacement

[wsp2]

I need to replace the water inlet, but unfortunately the replacement is slightly larger than the previous one. Jabsco for some reason decided to replace the old style which needed about a 3 1/8" hole with one that's about 3 1/2". I have a couple of questions I'm hoping I can get some feedback on:

- I was thinking about using this method to drill a larger hole: https://youtu.be/vOUfFaIJUqo?si=wP9k6RR7aC-3mwpc. The transom where the inlet is has fiberglass which is about 1/2" thick. Will this method be okay to enlarge the hole?

- Will I need a diamond or carbide tipped drill bit, or will a bi-metal one work okay on the fiberglass? https://www.homedepot.com/p/Milwaukee-3-1-2-in-Hole-Dozer-Hole-Saw-49-56-9641/202327759

- Regarding the plumbing part of this, is it okay to attach the inlet to any cold-water pipe? It appears the inlet pipe had broken off and was capped off somewhere, so I'm not 100% sure where it originally was fed into the system. I'm thinking it was attached to near where the cold water faucet is on the aft shower.

Thanks for any input! Boat is a 1995 440 aft cabin.

[Midnightsun]

Bi metal is fine. Sounds odd but start by running the drill in reverse to score the fibreglass and then put it in forward to make the hole. Highly suggest you have a helper holding the end of a shop vac near the hole cup saw while cutting.

This is a better method IMHO. https://www.youtube.com/watch?v=Ylbwpk2ZyO0

[Viper]

More than one way to do it, either way mentioned works fine. You can tap into any one of the cold water lines.

[paulr]

There is an arbor out there that 2 hole hole saw bits can screw on to. You put the 3 1/2" hole saw on first, then screw on the 3 1/8"
The 3 1/8 will keep the bit perfectly centered in the existing hole, then the 3 1/2" will begin to cut. Bi metal is perfect.

[paulr]

Here is an example of a dual hole saw arbor on amazon.