Mercury 80 Owner's Manual

OUTBOARD INSTALLATION
70
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.
18961
a
b
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.
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
b
20860
a - Large transom washer b - Transom reinforcement plate
Description Part Number
Large transom washer 67-896392
Transom reinforcement plate 67-896305
1. Apply marine sealer to shanks of bolts, not the threads.
2. Fasten the outboard with the correct mounting hardware. Tighten locknuts to the specified torque.
NOTE: For more accurate torque, whenever possible turn/tighten the mounting locknuts rather than turning the
mounting bolts.

Mercury 80 Specifications

General

Steering	Remote
Shaft Length	20 in (508 mm)
Gear Ratio	2.07:1
Horsepower	80 hp
Full Throttle RPM Range	5000-6000 RPM
Bore x Stroke	3.15 x 3.15 in (80 x 80 mm)