Motor Mount Block

My motor mount wood block broke from old age on the boat I just got....badly split and rotted. FS sells same replacement made of poplar wood. Has anyone made one yourself out of any other wood like oak. Any comments on best type of wood to oak, maple, or marine plywood and where to purchase it. The size was 6"high x 11" wide x 1.5" thick...actually two 3/4" pieces glued together.

In my opinion, if you keep the motor mount from getting wet then just about any hardwood will do.
If you're keeping it out in the weather, some commonly available decay-resistant species are white oak, black walnut, black cherry and mahogany.
Marine plywood is probably more expensive than these.