Bell, who was playing in his second Senior Amateur, became the first player since 1998 to win this title in his home state.
'Outside of marrying my wife, this is the greatest day in my life,' Bell exclaimed. 'I love this trophy. Can I keep it?'
McGraw, playing in this event for the first time, opened the match double-bogey, bogey to quickly fall 2-down. Another bogey on the sixth dropped him to 3-down.
Bell, who got into the field when Jerry Jackson withdrew due to health reasons, then bogeyed the par-3 seventh, but was again 3-up when McGraw could do no better than double-bogey on the eighth.
McGraw posted the first birdie of the match at the par-5 10th and that got him within 2-down. Bell faltered to a double-bogey on 12, and his lead dipped to 1-up. McGraw drained a 15-foot birdie putt on the 15th, then Bell missed a similar length putt to square the match.
The duo halved the next two holes before McGraw two-putted for bogey at the last. Bell blasted out of a greenside bunker to 8 feet and calmly drained the par putt for the win.
'My friends ask why I practice and don't play and I told them that I wanted to have a chance at being the Senior Amateur champion,' admitted Bell. 'Everybody thought I was crazy, but I kept getting better. So to actually win it is beyond my wildest dreams.'
McGraw was one of six players who survived the seven-way playoff Monday morning to advance to match play.
'I made lots of mistakes. I played very poorly today,' McGraw explained. 'I wasn't nervous. I didn't get it done. I didn't get it in the hole when I needed to.'