During a local pleasure flight the pilot noticed the engine oil temperature indication was rising. He reduced the throttle and then smelled something and saw smoke coming from under the instrument panel. He opened the window to alleviate the smoke. About 3 to 4 minutes from the airport, the engine lost power and the pilot performed a forced landing to a golf course. The nose landing gear collapsed during the forced landing resulting in substantial damage to the airplane's firewall. Examination of the airplane subsequent to the accident revealed that the aft portion of the muffler was separated from the assembly allowing hot exhaust gasses to enter the engine compartment. The magneto P-lead wire was melted and shorted to the airplane structure.