The 17-year-old Kolkata lad, currently ranked second on the Indian Golf Union Men's order of merit, had a four-day total of nine-over 289 (70,74,73,72) at the Par-70 course to share 46th position with American duo Kyle Rodes and Taylor Funk and New Zealand's Josh Munn.
Currently 43rd in the World Amateur Golf Rankings, Madappa became the first Indian to play in this prestigious event on the basis of his world rankings.
The four-day stroke play tournament saw fierce competition between 80 amateurs from the United States, Canada, Australia, New Zealand, Argentina, India and France.
"Nine-over is not something I had in my mind this week. Since I have played in the USA earlier this year, my plan was to finish at least in top five. I wish I could have converted some more shots into birdies from day one and shoot some low scores. Overall, It was a good experience playing in a field where Phil Mickelson has played in his younger days," he said.
American Danny McCarthy was victorious with a par in sudden death play off at 57th Porter Cup, which was delayed by nearly three hours due to rain.