Main Bearing Clearance, Plastigauge Method - Mercury MerCruiser Service Manual

Engine Inspection and Assembly
12. Tighten the rear main bearing cap. Using the following method:
Preferred method:
a. Do the first step torque on the rear main bearing cap.
Description
Crankshaft (main) bearing cap bolt—preferred
method
b. Using a lead hammer, tap the end of the crankshaft to the rear.
c. Using a lead hammer, tap the end of the crankshaft to the front.
d. Do the second step torque on the rear main bearing cap.
Description
Crankshaft (main) bearing cap bolt—preferred
method
e. Do the final step torque on the bearing cap.
Description
Crankshaft (main) bearing cap bolt—preferred
method
13. Check the crankshaft end play.
14. Install the rear main seal retainer and seal.
15. Check the clearance for each connecting rod bearing. Refer to Connecting Rod Bearing Clearance, Micrometer Method
or Connecting Rod Bearing Clearance, Plastigauge Method.

Main Bearing Clearance, Plastigauge Method

To obtain accurate measurements while using plastigauge or its equivalent, the engine must be out of the boat and upside
down so the crankshaft will rest on the upper bearings and the total clearance can be measured between the lower bearing and
journal.
To ensure the proper seating of the crankshaft, all bearing cap bolts should be at the specified torque. In addition, the surface
of the crankshaft journal and bearing must be wiped clean of oil.
NOTE: When checking the number 1 main bearing, loosen the accessory drive belt to prevent obtaining a tapered reading with
the gauging plastic.
1. Remove the bearing cap and wipe any oil from the journal and bearing cap to be inspected.
2. Place a piece of gauging plastic the full width of the bearing and parallel to the crankshaft centerline as shown.
b
IMPORTANT: The bearing caps must be tightened to the specified torque to ensure correct measurements. Do not rotate
the crankshaft with the plastigauge installed.
3. Install the bearing cap and evenly tighten the main bearing cap bolt or stud to the specified torque.
Description
Crankshaft main bearing cap bolt—preferred method
4. Remove the bearing cap. The flattened gauging plastic will be found adhering to either the bearing cap or the journal.
Page 3B-20
Main bearing plastigauge measurement
a
a - Gauging plastic
b - Bearing journal
19550
© 2016 Mercury Marine
Nm
15
First
Nm
40
Second
Nm
Final
Nm
15
First
40
Second
Final
90-8M0099748 eng DECEMBER 2015
lb‑in. lb‑ft
132.7 –
lb‑in. lb‑ft
– 29.5
lb‑in. lb‑ft
+90°
lb‑in. lb‑ft
132.7 –
– 29.5
+90°