The first scheduled service on your new Mercury outboard should be performed after it has been properly broken in and has approximately 20 hours of run time. It is important to keep a log of your run time, either in a notebook or on your phone after each use. Remember that an 8-hour day of fishing may only equal 10 to 20 minutes of actual run time. Keep that log until you have completed the full 20 hours, and then perform the first service on the engine.
After the initial service, most anglers will service the motor annually. However, if you fish 5-7 days a week or do a lot of trolling with the outboard, you may need to increase the frequency of service. For heavy users, service should be performed every 100 hours.
Even if you don't put anywhere near 100 hours on an engine per year, it is still recommended to perform yearly service. Water can enter your lower unit or engine oil without your knowledge. If this happens and you live in a cold climate, freeze damage can occur. In warm climates, damage to the internal workings of your engine can still occur. To prevent these issues, it is suggested that you perform maintenance every fall to ensure that your engine is in good condition going into winter.
If, during service, you find water in either the lower unit or engine oil, it is probably time to visit an authorized Mercury outboard dealer. They can test for seal failure and repair it before major damage occurs. This is much cheaper than waiting until the motor locks up, as those types of repairs can be very expensive.
By performing regular service, your Mercury outboard will be there for you season after season.