Yamaha F90 F100 F115 Diagnosing a Bad Trim Relay or Bad Trim Motor Outboard Specialty Tools

Is it bad trim motor, trim relay or wiring issue that caused this Yamaha F90 to stop working? How to isolate and diagnose without dropping a fortune on tools or a tech. Isolating the cause of electrical failure is crucial, and is one of the biggest sources of wasted time, money and effort for all technicians whether the tech is a professional or a boat owner doing their own repair work. Electrical diagnostic and repair/replace sequence (featured in upcoming part 3 of this series) is applicable to nearly all Yamaha outboards 50 HP and up. The OST-0022 spanner is used on F50, F60, F90, F115XB, all F115 after 2015 which have nearly identical Tilt Trim units. Using OST-0022 47mm spanner wrench to begin the cylinder/seal repair in the field by spinning the main cylinder cap loose before removing the tilt trim unit from the transom brackets and taking unit to the shop for tear down and re-seal (featured in part 2 of this series). WARNING: Regardless of what you see in this video, always be aware and use best practices to maximize your safety and the safety of others in the work area. Verify that the outboard is securely immobilized in its service locks (and that the service locks are actually working) before placing hands or other body parts under a raised motor where they will be crushed if the motor is allowed to free fall. Be extremely cautious when connecting any load/electrical wiring device to any source of hot/ground voltage since connecting to the wrong stuff can cause more problems that you had before you started the job! As you will see in these videos, connecting to an already hot circuit will usually produce an arc, which coupled with ambient fuel vapor will cause a large explosion. Before attempting to diagnose/repair electrical system components, some of which will need to be powered up for a good diagnostic, ALWAYS VERIFY THAT ALL SOURCES OF FUEL AND SPECIFICALLY FUEL VAPOR HAVE BEEN SEALED AND/OR COMPLETELY REMOVED FROM THE WORK AREA!