I am following Trepp's grab bag break in article. Here's a cut and paste:
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For the first ten (10) hours of operations an approved 2 cycle oil is to be mixed 50 to 1 with the fuel (1 pint for 6 gallons of gas) in additional to the oil injection system. If you do not run your gas tank (with the 50 to 1 mixture) empty in the first 10 hours, get it as low as you can before refilling the tank. I ran mine down to about 1/8th and then refilled and have not had a problem.
First ten (10) minutes of operation
1. Operate the engine at fast idle ONLY. This is a great time to check the workings of all of the live/bait wells and get familiar with the boat while floating.
2. Verify water pump operation by looking for a steady stream at the water pump indicator (water squirting out of pee hole).
Remainder of first hour (next 50 minutes)
1. Do not operate above half throttle (no more than 3500 rpm’s).
2. Change engine speed every 15 minutes by at least 200 rpm’s.
Second Hour
1. Use full throttle to bring boat on plane, then reduce speed to three quarters (3/4) throttle. Be sure boat remains on plane.
2. At intervals, apply full throttle for one to two minutes, returning to three quarters (3/4) throttle for a cooling period.
3. Change engine speed every 15 minutes by at least 200 rpm’s.
Next Eight (8) hours
1. Avoid continuous full throttle operation for extended periods of time.
2. Change engine speed every 15 minutes by at least 200 rpm’s.
This concludes the break-in period. After 20 (hours) of operation, service for break-in period is recommended by the manufacturer (Mercury).
NOTE - ALWAYS VERIFY WATER PUMP IS OPERATING. If the boat/motor does not have a water pressure meter, look for a steady stream at the water pump indicator (water squirting out of pee hole).
NOTE - NEVER OPERATE MOTOR OUT OF THE WATER</i>