Mercury 40 FourStroke Maintenance And Installation Manual page 100

Use a dial torque wrench to determine transom strength. If the bolt or nut
continues to turn without the torque reading on the dial increasing, it is an
indication that the transom is yielding. The load area can be increased by using
a larger washer or a transom reinforcement plate.
a
a - Large transom washer
b - Transom reinforcement plate
Fastening the Outboard to the Transom
IMPORTANT: The transom mounting surface must be flat within 3.17 mm
(0.125 in.). No step in the transom mounting surface is allowed. The inside
transom mounting bolt washer surface must be flat within 3.17 mm (0.125 in.).
a - Step (not allowed)
b - Gap between transom clamp and boat transom (not allowed)
INSTALLATION
90
b
33962
eng