I have a older colman serial # 027960654 furnace that had quit working its
Model 3115B750
Voltz 240 vac/60/1
Elements KW/Amps 14.0/58.0
Max motor 63
Max Circuit 80
Max fuse 90

Is doesn't say how many BTU's it is.

My question is... Will a 15 kw 53,000 BTU furnace work as a replacement for my older furnace if it fits where my other one was??

It should work but I would also check the wire size to make sure it is correct for the new unit.