This photo shows the original damage (without the motor).  Notice how the bolts and washers pulled through the transom.  The motor is somewhere on the bottom of Lake Erie.  On the outside shell,  I marked where the horizontal crossbeam is located and also where the vertical gussets are, so that I could tie into them later.

This photo shows the cutaway view of the inner shell after the outer shell and core were cut out.  The 4 holes were then patched with multi layer fiberglass matting and epoxied.  The perimeter sections were then scarfed back every 2" and routered to accommodate for the 3 layers of marine plywood that will replace the old transom.  Notice where I've marked the location of the crossbeam and gussets for attachment of the plywood.

This photo shows the marine plywood after installation.  The stainless screws were fastened into the crossbeam and gussets.  The plywood was epoxied on the inside and along the edges using West Systems Epoxy with Colloidal filler. Again, the crossbeam and gusset locations are marked for the next layer of plywood

This photo shows the 2nd layer of marine plywood installed complete with stainless screws, epoxy, and markings for the final layer of plywood.

 

This photo, showing the 3rd and final layer of marine plywood, also illustrates where the bottom 1 1/2 " of the plywood was routered out to allow for multi layers of fiberglass and epoxy.  This area needed extra support and strength due to its location where the majority of the torque from the 225 HP motor will occur.

This photo shows the final layer of fiberglass extending 2" beyond the plywood.  West Systems Epoxy was used for final filling and countour, then sanded flat before the epoxy primer was applied

Here the epoxy primer has been applied but before it was block sanded flat to contour.

This is the finished transom after application of the polyflake and clear gel-coat.  Again, it was sanded flat and straight to contour then compounded and polished to a high gloss finish.