Mercury 50 4-Stroke Manual page 113

OUTBOARD INSTALLATION
2. Drill four 13.5 mm (17/32 in.) mounting holes.
Checking Boat Transom Construction
IMPORTANT: Determine the strength of the boat transom. The
outboard mounting locknuts and bolts should be able to hold
75 Nm (55 lb. ft.) of torque without the boat transom yielding or
cracking. If the boat transom yields or cracks under this torque, the
construction of the transom may not be adequate. The boat
transom must be strengthened or the load carrying area increased.
a - Transom yielding under bolt torque
b - Transom cracking under bolt torque
When first determining transom strength, use a dial torque wrench.
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
105
3973
b
18961