Throttle cable length unknown

I have a 98 stratos 273 vr that I purchased a little over a month ago and it's my first boat I've owned. I recently bought a hot foot for it and I'm planning on installing it myself. I have ran into a couple of problems though. I have seen that everyone is saying instead of removing old throttle cable just drop it into the boat in case of hot foot failure. Only problem is I cannot figure out how long the throttle cable needs to be for the hot foot. And the second problem is, are half inch screws long enough or too long to install hot foot. I want it to be secure but I also don't want to drill through the hull. Any comments will be great!

I just installed a PRO hot foot in my 285 PRO. Used 1.25 #14 screws. I used a 15' throttle cable.

There should be a part number on the old throttle cables and the last 2 digits will be the length. Just take the length and add 2 feet to it and order a new one.