Attaching the new transom core

[Normagain]

Two things. Coosa is not a porous foam, much less so than plywood, so it will not soak in much of any resin, but plenty enough for bond strength

As for temps, that temp is perfect because you will have a better working time. If you have sun after completion, put a tarp over the area when done and you will have plenty of curing heat. You can do this the day after for final cure. Most if not all epoxy will be curing at above 40 but slowly at that temp. You should try to keep the resin itself at the recommended temps for mixing however in order to get the reaction going and also for it to dispense well if using dispensing pumps.