Mercury 40 4-Stroke Manual page 78

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
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.
NOTE: The inside holes on the transom reinforcement plate are for the lower transom bolts and the
outside holes are for the upper transom bolts.
a - Large transom washer
Description
Large transom washer
Transom reinforcement plate
OUTBOARD INSTALLATION
a
a
b - Transom cracking under bolt torque
b - Transom reinforcement plate
72
b
18961
b
20860
Part Number
67-896392
67-896305