During production the transom is fabricated in the mould with the lay-up schedule i

ncluding the plywood as an integral part of the transom. Typically the engine mounts,

many are made from plywood covered with fiberglass, are also installed at this stage

of production. Once frames and supporting structures are completed the hull is

removed from the mold. The next step includes the engine installation. A section

 of the transom, (hole through the transom), is cut out to facilitate the various

transom assemblies. Transom assemblies are the units which are secured to the t

ransom and support the stern drive unit.  When the hole is cut to fit the

transom assembly the circumference of the hole shows exposed fiberglass

laminate and plywood. The plywood, in many cases, does not get sealed properly.

As this hull penetration is partially or in many cases completely underwater

it is vulnerable to the elements and ultimately water infiltration to the plywood core

is the next step. How fast the plywood rots away depends upon several factors, they

include; the climate, the various types of insects indigenous to the area, how long

the boat is in the water each year, and how many hours  the boat is under way each

year, and lastly, how the boat is stored,  protected, and ventilated during winter

lay-up. It usually takes many years for severe damage to occur in this area,

but not always. I recently inspected a three year old Bayliner with twin out drives

that had actually pulled away from the structure about an inch. The owner

called me to check out the transom because he did not recognize the new

protrusion at the stern drive that had somehow occurred over the winter.