Original transom material

[afterhours]

Quick question. What is the original transome core material on a 70's era potter hull 20sf? Marine plywood? Balsa?

I've seen many threads and photos about redoing the transom, but I've never run across a mention of the original core material. The photos of the deteriorated wood suggest some type of chipboard. The reason I ask, is I'm going to redo the transom, raise it 5" and hang a 2001 Honda 90hp 4s on the back. I'm leaning toward using marine ply because of my limited budget, but I'm a little concerned about weight. Considering spending a little more money on material if the final weight with motor will get me closer to the original motor package and thus similar CG and weight distribution. Seeing as I'm only putting 90hp on there, I'd like to try to get as close to designed CG as possible to improve performance.

Also, switching out the Honda for a lighter motor is a non-starter. The Honda and a doner are free from my brother. I bought this hull to fit the motor and get me offshore 15-20 miles in the Gulf and back again to see my family with some fish for dinner.

Any input is appreciated. One I begin the rebuild I'll start a thread and post photos of the progress.