Caulking question?

Question

i'm attaching a new board to the back of my aluminum boat for the motor what caulking/adhesive would be best for this

Answer 1

3M 3200, commonly known in the trade as "seagull ****".

Answer 2

I do believe the product made by 3M is 5200.

It is available in different size tubes and a cartridge tube.  It is also available in a fast set formula.  

From  3M's web site:

The high performance polyurethane becomes tack free in one hour and fully cures in approximately 24 hours. The seal is extremely strong, retains its strength above or below the water line. Stays flexible and allows for structural movement. Has excellent resistance to weathering and salt water. Easy to apply

Answer 3

Don't use anything else but 5200 myself.

What is this board for?