200 – 250 HP – 76 Degree V6

1. What is the gear ratio of this lower unit?

This lower unit is available with a 1.75:1 or 1.86:1 gear ratio. Verify your engine’s required ratio before ordering.

2. Is this lower unit compatible with both two-stroke and four-stroke engines?

This lower unit is designed specifically for 76-degree V6 Yamaha two-stroke outboard engines in the 200-250 HP range. Compatibility with four-stroke models may vary.

3. Does this lower unit come with a water pump installed?

Yes, a brand-new water pump assembly is pre-installed to ensure optimal cooling and performance.

4. What type of gear oil should I use for this lower unit?

Use Yamaha-approved marine gear oil or SAE 90 API GL-5 marine gear lubricant for best performance and longevity.

5. What is the driveshaft length on this lower unit?

This lower unit is available in multiple shaft lengths (20″, 25″, 30″). Ensure you select the correct shaft length for your outboard.

6. What torque specifications should be used when installing this lower unit?

Refer to the Yamaha service manual for exact torque values, but typical mounting bolt torque ranges from 35-45 ft-lbs.

7. Is this unit equipped with forward, neutral, and reverse gears?

Yes, the unit includes a fully assembled gear set for smooth shifting between forward, neutral, and reverse.

8. What are the primary materials used in this lower unit?

The casing is made from marine-grade aluminum, and the internal gears are hardened steel for durability.

9. Is this unit pre-filled with gear oil?

No, the unit ships dry. You must fill it with marine-grade gear oil before use.

10. How do I properly break in this lower unit?

For optimal performance, follow these break-in procedures:

• First 10 hours: Operate at half throttle, avoiding sudden acceleration.
• After 10 hours: Gradually increase throttle but avoid prolonged full-throttle operation.
• After 20 hours: Change the gear oil to remove any break-in debris.

11. Does this lower unit use a standard propeller shaft spline?

Yes, it features a 15-spline propeller shaft, compatible with most Yamaha propellers designed for 200-250 HP models.

12. What shift shaft configuration does this unit have?

This lower unit comes with an adjustable shift shaft, allowing compatibility with various Yamaha models.

13. How do I check for correct installation and alignment?

• Ensure the driveshaft and shift shaft align properly.
• Apply marine grease to splines before installation.
• Torque mounting bolts to OEM specifications.
• Verify proper shifting through forward, neutral, and reverse before starting the engine.

14. What should I do if my lower unit leaks oil?

• Check the drain and vent plugs for tightness.
• Inspect seals and gaskets for damage.
• Ensure propeller shaft seals are intact and not leaking.

15. What cooling system components are included?

This lower unit includes an impeller, housing, and water pump assembly to ensure proper cooling performance.

16. What is the recommended maintenance schedule for this lower unit?

• Every 100 hours or annually: Change the gear oil.
• Every 200 hours: Inspect and replace the impeller if needed.
• Every 300 hours: Check seals and bearings for wear.

17. What should I do if the lower unit makes unusual noises?

• Check for low gear oil levels or contamination.
• Inspect the propeller shaft and bearings for damage.
• Ensure proper alignment of the shift shaft.

18. What is the max RPM this lower unit can handle?

This unit is built to withstand 5,500 – 6,000 RPM, matching Yamaha OEM specifications.

19. Does this lower unit have a water intake modification for high-speed use?

Yes, it features standard side water intakes, designed for efficient cooling at high speeds.

20. Can I swap my old lower unit’s internal parts into this unit?

No, this unit comes with a fully assembled and sealed gear case, and swapping internal components may void the warranty.

21. Mercury lower unit Serial # 1B279834 – Model # 225cxxl4s – HP: 225 – Year: 2006 – 30″ shaft. It’s counter rotating but If possible I need standard rotation same lower unit.
90-421 is what you need – choose 4 stroke and 30″ shaft. If you look it up, you will see Yamaha made these motors for Mercury, so it is a Yamaha lower unit.

16. What is the difference between the 90-421 and the 90-422 are they interchangeable as long as they have the same shaft length?

Physically the 421 and 422 share the Yamaha V-6 bolt pattern, driveshaft spline and shift-shaft geometry, so a 20-, 25- or 30-inch version of either unit will bolt to the same mid-section.

However, two points keep them from being true drop-in substitutes:

1. Gear ratio mismatch – Swapping a 1.81-ratio 421 onto an engine that expects the 2.00-ratio 422 (or vice-versa) will change prop-shaft rpm ±10 %, which can over-rev the motor or lug the prop.

2. Cooling circuit – The 422’s water-cooled bearing-carrier needs the little cooling hose that later F-series mid-sections provide. Older 2-stroke mids lack that hose, so the carrier would run dry; conversely, fitting a 421 to an F250 blocks that cooling line.

• Use 90-421 for the 3.1/3.2 L 2-stroke and the early F-series engines that originally had a 1.81 ratio, single-pickup case.

• Use 90-422 for the later F225/F250 engines that left the factory with a 2.00 ratio, dual-pickup, water-cooled-carrier case.

• Do not select by shaft length alone; check your engine’s original gear-ratio and whether it has the cooling hose to the carrier before ordering.

Because of those two differences SEI and Yamaha both say match the gear-case number to the engine family, not just the shaft length. Only the few “crossover” F250 model years that originally came with a 421 style case can run either one safely. In simple words:

• 90-421 = Older style, faster gear (1.81:1), no cooling hose, side water pick-up only.

• 90-422 = Newer style, correct gear (2.00:1), has cooling hose, dual water pick-up.

Use 90-422 if your engine came with a cooling hose and 2.00:1 gear ratio — like your 2003 Mercury 225 4-stroke.

This OEM-grade Yamaha 76-degree V6 lower unit is the perfect replacement for a wide range of Yamaha outboards, including Yamaha 200 HP V6 lower unit replacement and Yamaha V6 225 HP lower unit replacement models. Engineered to deliver factory-like performance, it’s fully compatible with popular units like the Yamaha Z250TXR lower unit replacement, as well as SX225 and SX250 lower unit replacement needs. Designed to fit 76 Degree V6 Yamaha outboard lowers, this unit also serves as a direct replacement for Yamaha F225XA 4-stroke lower units and F200XA lower units, making it one of the most versatile options on the market. Available in 30″ shaft lower unit configurations and fully assembled for hassle-free installation, this replacement ensures you get back on the water with confidence and durability that lasts.