Lucas Schott was a distant second while 2014 tour champion Jeff Taylor used multiple lines in racing from 10th starting to third.
Jason Grimes started 17th and finished fourth; rounding out the top five was Jason Wolla.
Marriott was already on the Fast Shafts All-Star Invitational ballot. Seventy-four Modified drivers from a dozen states and Canada were entered at Williston. Eight states and Saskatchewan were represented in the main event.
Joren Boyce, a former Modified tour champion, passed Matt Speckman on the fourth circuit and led to the end of the 20-lap IMCA Sunoco Stock Car feature.
Three cautions slowed the early going but the race stayed green the last 17 laps. Boyce beat Speckman across the stripe by a car length. Andrew Altenburg was third.
Features at Williston were the first held in the 27th annual tour, following rainouts at Jamestown Speedway, Nodak Speedway and Estevan Motor speedway.
Dacotah Speedway at Mandan hosts both the Thursday, July 14 tour date and the Friday, July 15 $10,001 to win Legendary special for IMCA Modifieds.
Heat winners were Hank Berry, Schott, Hatlestad, Bragg, Alvarado, Marriott, Jason Wolla and Tom Berry Jr.