Platform across a 9 foot span

Hogan-s

I am trying to build a platform on my boatlift in South Florida.
The platform will be submerged in salt water periodically.
The dimension of the platform will be 16' X 42".
It will be placed on the Aluminum beams of a boat lift.
I will be using pressure treated wood.
Possibly 3 peope will be on the platform at one time.
What is the wood dimension I need?
Will 2X6's on edge 3' apart be OK for the 9' span.
Will 1X4" flat with a 3" overhang for the 40" span.
Do I need to go to 2 X 8 or 2 X 10 and/or will 3 cross members be better.
Should I go to 2X6 for the the 40" span.

Thanks for any suggestions

BuiltByMAC

For your joists, 2x8 pressure treated Southern Pine on edge every 20" (3 total). If you want to use 2x6 pt Southern Pine on edge, space them every 8" (5 total).

For your decking, use 2x6 material, not 1x4.

Using stainless steel hardware, properly fasten your joists to your beams and properly fasten your decking to your joists. Obey all local codes.


Mac