When I speak to boat owners about a range of motor maintenance subjects, I often find myself saying that they should change their gear lube. Changing the lubricant in the motor’s gear case is standard procedure when performing an annual service, but it is also prudent to perform this inexpensive and simple service more frequently. Regular maintenance on your boat’s engine is critical to its longevity and performance. In this column I am not going to instruct you how to change your own gear lube — you’ll need to have a qualified technician show you the procedure. However, I am going to help you to decide when to perform this service, learn how to recognizing any problems you may encounter with your gear lube, and better understand your mechanic’s findings when he performs this very important maintenance.

Most engine manufacturers recommend changing the gear lube at the first 20 hours and then every 100 hours or annually, whichever comes first. Also, you should change your gear lube if you are going to leave your boat sitting for any period of time — for example, if you are a seasonal resident and you will be leaving for three months or more. This is because if you have any salt water at all that has leaked into the gear case, you will probably return to a rusted and ruined gear case. If you are unfortunate enough to live where it is cold, any water trapped inside will freeze, which can crack the gear housing.