Yamaha F255TXRC Outboard Lower Unit Installation

Having serviced or repaired the lower unit on your Yamaha outboard, you’ll obviously need to reinstall the gearcase back onto the upper casing. 

Watch the video above and follow the steps below to learn how to install a Yamaha F225 lower unit. 

NOTE: We worked on a Yamaha F225 outboard motor, but the process is the same or similar for most outboard makes and models.

Tools and Supplies – Yamaha F225 Lower Unit Installation

Buy Yamaha F225TXRC lower unit assembly

Buy OEM Yamaha 2004 F225TXRC parts

How to Reinstall the Lower Unit to a Yamaha F225 Outboard

Step 1. Grease the shift shaft, the splines on the drive shaft and the water pump inlet.

Yamaha F225TXRC lower unit installation

Yamaha F225 lower unit installation

Step 2. Apply red threadlocker to the seven 14mm lower unit mounting bolts.

Step 3. Make sure the gearcase is in neutral by rotating the prop shaft back and forth, and rotating the shift shaft if necessary.

Step 4. Make sure the gearshift mechanism on the outboard is in neutral by looking to see if the mechanism is in the central position, and moving it to the center if necessary.

Yamaha F225 outboard lower unit install

Step 5. Pick up the lower unit, and carefully slide the driveshaft up into the upper casing. Make sure the shift shaft aligns with the linkage, and that the water pump aligns with the water tube. Then, slide the lower unit up until it’s seated on the upper casing.

Yamaha F225 outboard engine lower unit install

Yamaha F225 outboard motor lower unit install

Step 6. Support the lower unit so it doesn’t fall down, and install one of the lower unit mounting bolts. Once the first bolt is installed and tightened, you can stop supporting the lower casing and install the six other lower unit mounting bolts. Torque all seven mounting bolts to 34 foot-pounds.

Yamaha F225 outboard motor lower unit installation

Yamaha outboard motor lower unit installation

PRO TIP: To make steps 5-6 a bit easier, have someone support the lower unit for you while you make sure it’s aligned correctly, and install the first mounting bolt.

Step 7. Apply red threadlocker to the longer 14mm mounting bolt that goes in the trim tab well, then install the bolt and torque it to 34 foot-pounds.

Yamaha outboard motor lower unit reinstallation

Step 8. Install the trim tab, then install the 14mm trim tab bolt, torque it to 34 foot-pounds and you’re done.

Yamaha F225 outboard motor lower unit reinstallation

Yamaha F225 outboard engine lower unit reinstallation

Watch the video below to see our complete Yamaha F225 outboard rebuild.



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