This information below was found on the Yamaha Web site.
If you purchase your Yamaha outboard(s) from a non-Yamaha dealership or from an individual, then contact your local Yamaha dealership for warranty registration or transfer of ownership. A Yamaha authorized dealership will need to evaluate the outboard(s) to verify that they are in normal running condition. There may be a charge for these services.
If you are having a problem with your registration or ownership transfer, or if you would like verification of warranty coverage, please contact the Yamaha Outboard Customer Support line at (866) 894-1626.
Y.E.S. is a transferable contract, so you can transfer Y.E.S. to a subsequent customer. This leads to increased resell value for your Yamaha. It is required that a transfer of registration and inspection be performed by a Yamaha dealer.
When you purchase a new boat, the Yamaha Dealer will fill out the warranty information on line, and Yamaha will send you a Factory Warranty Card. Warranty coverage is found on the back of your dealer manual, and if at any time you want to know how much time you have left on your warranty, just call the Yamaha Outboard Customer Support line at (866) 894-1626 and give them your Primary Identification Number (PID). If you don’t have your warranty card, you can find the PID number on the port side of the engine.
The information below is what I recommended when I was a tech.
The trim ram leaks are more common in saltwater area's. Rinsing with fresh water and applying a thin layer of anticorrosion grease helps keep the salt build-up and corrosion from damaging the seals. This is hard to do if the boat is in the water but I always would recommend the effort. Another procedure that is over looked by many outboard owners is retracting the trim rams when not in use. This is done by trimming the engine in the full up lilt position. Then using the tilt locks to hold the motor tilted in this position. Now retract the trim rams using the down Botton until the trim rams are fully retracted. This puts the ram's cylinders in the protected side of the seals helping to prevent corrosion.