Hi!

I've noticed that outboard motors which are permanently mounted,
especially on aluminium (and sometimes fibreglass) boats, have a thin
pad of material - either wood or plastic - between the motor itself
and the transom. In other words, the motor mounting bolts go through
the motor and the mounting pad before finishing up in the transom of
the boat.

What material should that pad be made from, assuming its going to live
on an aluminium boat in salt water, and have 100HP of Yamaha 4-stroke
engine trying to squeeze it into oblivion?

Since the pad is usually far too thin to add any real structural
strength to the transom (say 1cm), I guess the purpose of the pad is
to provide some electrical isolation between the motor itself and the
metal transom?

Perhaps the right material might also provide a modicum of vibration
dampening?

I've looked far and wide and I can find absolutely nothing on the
topic. Any and all info will be extremely welcome!

Torre