Mercury MerCruiser Drive Gear Needle Bearing 843240

Mercury MerCruiser Drive Gear Needle Bearing — 843240

What This Part Does

The 843240 is a genuine Mercury OEM needle/roller bearing assembly used in the upper driveshaft housing of selected high-performance MerCruiser Bravo sterndrives. It supports the rotating drive-gear assembly within the upper housing and works together with bearing race 861791 to maintain correct alignment and load distribution under the demands of high-performance marine operation. Mercury’s Quicksilver drive-system catalog identifies 843240 specifically as the drive-gear bearing for Bravo XR and Bravo XZ applications — it is not the general-purpose bearing for all Bravo sterndrives.

Compatible Applications

• Bravo XR — upper driveshaft housing drive-gear bearing position
• Bravo XZ — upper driveshaft housing drive-gear bearing position

Exact compatibility depends on the complete drive model and serial number range. Confirm by locating the Bravo XR / XZ driveshaft housing schematic for your specific drive and serial number, and verifying that 843240 appears at the drive-gear bearing position alongside race 861791.

Serial Number & Fitment Notice

Do not select this bearing based on horsepower or general Bravo identification alone. Mercury uses several different upper drive-gear bearings across the Bravo family:

• Standard Bravo I, II, III — use different upper bearing configurations (e.g., 815900 or others depending on serial range)
• Bravo X — confirm separately by schematic
• Bravo XR / XZ — 843240 (this part)

Confirm the sterndrive model, serial number, and upper driveshaft-housing schematic before ordering. Internal drive bearings are not returnable once installed — verify the diagram first.

Dimensions

Exact dimensions are not published in the Mercury consumer catalog. Confirm fitment via the Bravo XR / XZ driveshaft housing parts diagram for your specific drive model and serial number. Do not substitute based on physical measurements from bearings used in other Bravo variants.

When to Replace

• Rough or notchy rotation when the bearing is tested by hand
• Pitting, flaking, or spalling on the rollers or race
• Excessive radial or axial movement at the drive-gear position
• Heat discoloration on the bearing or surrounding housing
• Metal contamination found in the drive lubricant during a drain
• Water intrusion corrosion on the rollers or cage
• Damage following drive-gear failure or upper-housing damage

A failed bearing can damage the corresponding race (861791) and the drive gears. Inspect all related components when the upper housing is disassembled — replace the bearing and race together if either shows damage.

Service Interval

Inspect this bearing during any upper driveshaft-housing disassembly or at any overhaul interval. There is no calendar or hour-based replacement interval under normal operation. Replace immediately if rough rotation, metal contamination in the drive fluid, or gear noise is found. Preventive replacement of the bearing and race together is recommended whenever the upper drive is fully disassembled.

Installation Notes

• Inspect bearing race 861791 for pitting, scoring, or spalling — replace race and bearing together if either is damaged
• Check the drive gears for abnormal tooth wear, chipping, or stress marks
• Inspect the upper housing bearing seat for damage or fretting
• Check seals for evidence of water intrusion into the upper housing
• Flush any metallic contamination from the housing before reassembly
• Verify bearing preload and gear setup using the applicable Mercury service procedure for the Bravo XR / XZ
• Use the correct Mercury installation tools where specified — pressing a needle bearing without the correct driver can damage the cage or rollers
• Do not reuse a damaged race with a new bearing

Alternate & Superseded Part Numbers

• 843240 — Mercury / MerCruiser OEM number
• 31-843240 — Mercury bearing-prefix catalog format

No superseding number is confirmed. Do not substitute bearings from other Bravo variants without verifying the current drive-specific parts catalog for your serial number.

Related Parts

• 861791 — bearing race (used with 843240 in applicable assemblies)
• 861787 — thrust bearing
• 861209A1 — bushing kit
• 865866 — shift-shaft oil-seal plug
• 127091 — seal
• 8M0204693 — seal

Technical FAQ

Q: Can I use this bearing in a standard Bravo I, II, or III?
A: Not without confirming it is specified in the driveshaft-housing schematic for your specific Bravo model and serial number. Mercury identifies 843240 for Bravo XR and XZ applications. Standard Bravo I, II, and III use different upper-bearing configurations. Using the wrong bearing in a high-load drive application can result in premature failure.

Q: Do I need to replace the bearing race (861791) at the same time?
A: Yes, as a strong recommendation whenever the bearing shows any sign of damage, pitting, or wear. A new needle bearing running on a worn or pitted race will fail prematurely. If there is any evidence of bearing failure — metal in the drive fluid, rough rotation, or noise — replace both the bearing and race together.

Q: Is 843240 the same bearing used in the Bravo X?
A: Not confirmed. Mercury specifically identifies 843240 for Bravo XR and XZ applications. The Bravo X should be confirmed separately using its own driveshaft-housing schematic and serial number.

Q: What causes this bearing to fail prematurely?
A: The most common causes are water intrusion into the upper housing (from failed seals), metal contamination from a gear failure running through the drive fluid, and insufficient or contaminated drive lubricant. Always check and service drive lubricant at the recommended interval and inspect seals during any drive service.

Q: Is this a pressed-in bearing or a slip-fit?
A: Installation requires the correct Mercury press tools for the Bravo XR / XZ upper housing. Do not attempt to drive or press the bearing without the correct tool — improper installation can damage the roller cage and cause immediate failure under load.

Parts Desk Insights

The most common issue with 843240 is customers ordering it for a standard Bravo I, II, or III when they see “Bravo” in the description — this bearing is specifically for the XR and XZ variants. Always ask for the complete drive model and serial number before shipping an internal drive bearing. The other key point is that this bearing should almost never be replaced in isolation if there’s been a gear or lubrication failure — in that scenario, race 861791, the thrust bearing, and the drive gears all need inspection before the new bearing goes in. An internal drive rebuild is expensive enough that shipping the right parts the first time, and recommending the race alongside the bearing, saves a lot of grief later.