From the Yamaha outboard motor site.
What is the break-in period for my new four-stroke Yamaha Outboard?
New engines require a period of break-in to allow the mating surfaces of moving parts to mate evenly. Correct break-in, as described in your Owner’s Manual, will help your outboard provide proper performance and longer engine life. Yamaha’s four-stroke engines have a 10-hour break-in period as follows:
FOUR STROKE OUTBOARDS
Interval Procedure
1st Hour Operate the engine at varying speeds up to 2000 rpms or approximately 1/2 throttle.
2nd Hour Increase the engine speed until the boat is on plane (but avoid full throttle operaton) and then back off on the throttle while keeping the boat at a planing speed.
Next 8 Hours Run the engine at any speed however avoid operating at full throttle for more than 5 minutes at a time.
After the 1st 10 Hours Operate the engine normally.
The break-in maintenance is at 20 hours. For the 10 hours after the break-in and before the service you can operate the engine normally.
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