decking screw length?

Hi

I would like to know what length screw would be best to secure 19mm thick merbau decking board to treated pine joists? Should i get screws with a shank length equal to the decking board thickness ( ie. 19mm)

Thanks in advance.

The recommendations I've read suggest 65mm, but I've use 50mm screws on mine (2,000 of them) without any issues. On a coupl of occasions I did hit a knot or void in the joints and replaced the screw with a 75mm, but I could count those on my hands.

on treated pine i would use 45-50mm more than enough
regards chowcini

Thank you all for your responses.