All Viking engines now must use this idler pulley.
(Unless your engine was delivered after the 2014 model year)
Gates 36026 Drive Belt Idler Pulley
Use 12mm washers or fabricate a spacer to align pulley with crankshaft pulley.
Tape a 0.090 spacer to the crank pulley to compensate for the lip on the idler pulley. The use a straightedge firmly pressed against the crank pulley + spacer disk to align the idler.
See 0.090" shim on crank pulley in order to compensate for the idler pulley fatter lip.
Using the original bolt, we were able to add a single washer on the aft side of the pulley, 5 wahers between the pulley and the engine an no washers but thread locker on the nut side. If you would rather have a washer under the nut, turn the bolt around.
Be sure to add a washer here and do not support the pulley on the built in sleeve but rather the inner race of the bearing.