9412A23 Mercruiser Alpha One Gen One Driveshaft Housing | Genuine Used Part

🔧 Product Description

Genuine MerCruiser MC-I / R / MR / Alpha One Complete Driveshaft Housing - Part Number: 9412A23

A genuine MerCruiser complete upper sterndrive housing with a 1.98:1 gear configuration for selected MC-I, R, MR and Alpha One Gen I drives.

The assembly contains the upper gear set, universal-joint shaft, vertical driveshaft and related bearings and seals. It is primarily associated with MerCruiser inline-four engine packages.

⚙️ Key Features

• Genuine MerCruiser complete upper driveshaft housing
• Correct part number 9412A23
• 1.98:1 complete-drive gear configuration
• Fits MC-I, R, MR and Alpha One Gen I systems
• Suitable for standard-rotation four-cylinder packages

🚤 Compatibility

Commonly used on

• MerCruiser MC-I sterndrives
• MerCruiser R and MR drives
• MerCruiser Alpha One Gen I drives

Typically suits

• Engine models:
• MerCruiser 120HP 2.5L inline-four
• MerCruiser 120HP 3.0L inline-four
• MerCruiser 140HP 3.0L inline-four
• Selected early MerCruiser inline-six applications using the correct short universal-joint yoke
• Alpha One Gen I drives from approximately 1984-1990
• Pre-1983 MC-I and R applications when fitted with the required yoke and matching lower unit
• HP Range: Approximately 120HP - 165HP
• Engine Type: MerCruiser inline-four and specified early inline-six petrol engine
• Drive Type: MC-I / R / MR / Alpha One Gen I upper housing
• Gear Ratio: 1.98:1 OEM configuration; aftermarket replacements may be identified as 1.94:1
• Year Range: Approximately 1970s-1990, dependent on drive and universal-joint configuration

🔌 Function

The driveshaft housing receives power from the engine coupler through the universal-joint shaft and transfers it through the upper bevel gears to the vertical driveshaft and lower gear housing.

⚠️ Common Signs of Failure

• Upper gears or bearings produce a whining or grinding noise
• Universal-joint crosses are loose, rusty or seized
• Gear oil leaks from the input or driveshaft seals
• Water enters through failed bellows or sealing surfaces
• Splines, gears or bearing surfaces show excessive wear

🔄 Supersession & Cross Reference

OEM Supersession Chain

• 9412A23 → Supersedes 5523A65
• 5523A65 → Replaces earlier 3917A9 applications
• 9412A23 current reference for the applicable 1.98 upper assembly

OEM / Related Numbers

• 9412A23
• 1547-9412A23
• 5523A65
• 1547-5523A65
• 3917A9
• 1547-3917A9
• 39385A1 short universal-joint yoke for applicable early installations

Aftermarket / Verified Equivalents

• SEI Marine: 90-104-01A upper unit
• SEI Marine: SE106 1.94 replacement upper assembly
• Specialist remanufactured 9412A23 upper driveshaft housing

📦 Condition

• Genuine used part
• Removed from running drive where applicable
• In good working condition unless otherwise stated