Honda BF115A, BF130A Outboard Motors Shop Manual., Page 76Get this manual
10) Align themark on the balancer belt driven pulley (exhaust side) with the alignment mark on the timing belt lower cover LOWER COVER
11) Install new balancer belt on each pulley with care not to allow the alignment marks to come out of the alignment
121 BALANCER BELT
BALANCER B
After installation, check each pulley for proper alignmentAdjust the pulley alignment if necessary
12) Loosen the adjusting nut and the adjusting bracket bolt 213 to turn (i.eas loose as the tensioner is moved by the spring force) and adjust the balancer belt tensionThe balancer belt tensioner is the automatic adjustment typeDo not push the tensioner against the belt with your handDo not loosen the adjusting nut and the adjusting bracket bolt more than turn