How to Pressure Test Yamaha F225TXRC Outboard Gearcase

Having serviced and rebuilt the lower unit on your outboard, you'll want to pressure test it to make sure all the seals are functioning effectively before reinstalling it to the motor.

Use our Yamaha F225 lower casing drive parts diagram for reference, and watch the Yamaha F225TXRC outboard gearcase pressure test video above to get this job done.

Tools Needed - Yamaha F225 Gearcase Pressure Test

• Screwdriver
• Pressure tester

NOTE: We pressure-tested a Yamaha F225TXRC outboard, but the process is virtually the same for most outboard makes and models. 

Pressure Testing a Yamaha F225TXRC Outboard Lower Unit

Step 1. Remove the upper oil level bolt.

Step 2. Attach a pressure tester to the lower unit via the oil level bolt hole.

NOTE: You'll need to use the correct adapter for the pressure tester to fit the bolt hole.

Step 3. Use the pressure tester to increase the pressure within the gearcase to about 12psi to 13psi.

Step 4. Leave the gearcase alone for a few minutes, then check the pressure. If the PSI level remains the same, the seals are holding and the lower unit can be reinstalled on the motor. If the PSI level has dropped, a seal is leaking and will need to be reseated or replaced.

PRO TIP: To find a leaking seal, spray the seals with a mixture of water and detergent or soap, then pressurize the lower unit. Bubbles will appear at the leaking seal.

Step 5. Remove the pressure tester and reinstall the oil level bolt.

Having issues with the lower unit on your outboard motor? Check out the video above for some lower unit troubleshooting tips to help you diagnose and correct the problem.