rebuild and repair help 88 cajun

I have a 1988 Cajun bass fishing machaine that a got from my dad a few years back. The transom was in bad condition and some of the wiring and gauges don't work. I put it in the St. Johns a few times but was worried about the transom and it has sat in a storage compond for a year and a half. The standind water due to it not draining and weather took a toll. I want to get the thing running again due to it being my dad's instead of just getting rid of it and my main concern is rebuilding the transon. I've ripped out all the carpet and plan on putting down a non- slip surface and running it in the intercoastal for saltwater fishing. Any thoughts on the repair of some rot under the carpets in the front and the possible need to remove the cap to replace the transom. Was thinking of using seacast. Hoping it will hold up to the 150 Merc on it if I could get it running again.

Thanks for any input and I will try and post some pictures of the process.