1666-8833T15 Mercury Long Shaft Gearbox | Genuine Used Part

🔧 Product Description

Genuine Mercury / Mariner 6HP-15HP 20-Inch Long-Shaft Complete Gearcase - Part Number: 1666-8833T15

A genuine Mercury black-finished complete lower unit for selected 6HP, 8HP, 9.9HP, 10HP and 15HP two-stroke outboards. The assembly uses the small 2.00:1 gearcase family and a 20-inch long driveshaft. It includes the gear housing, driveshaft, propeller shaft, forward and reverse gears, pinion, clutch and water-pump section when supplied complete.

⚙️ Key Features

• Genuine Mercury Marine complete long-shaft gearcase
• Correct service number 1666-8833T15
• 20-inch / long-shaft configuration
• Standard propeller rotation
• Nominal 2.00:1 gear ratio

🚤 Compatibility

• Mercury and Mariner 6HP two-stroke model families
• Mercury and Mariner 8HP two-stroke model families
• Mercury and Mariner 9.9HP, 10HP and 15HP two-stroke model families
• USA serial ranges 0G760300-0T979999, 0T980000-0T999999 and 1B000001 onward where 8833T15 is listed
• Belgium serial ranges 0P017000-0P325499 and 0P325500 onward where the same unit is specified
• Exact fitment is controlled by serial number, shaft length and shift-linkage design

🔌 Function

The gearcase changes the vertical driveshaft rotation through the pinion and forward or reverse gear, transfers torque to the propeller shaft and houses the water pump that supplies cooling water to the engine.

⚠️ Common Signs of Failure

• Gear oil contains water or metal
• Unit jumps out of gear
• Propeller shaft is bent
• Driveshaft or shift-shaft splines are damaged
• Bearing noise or excessive backlash develops
• Water-pump pressure becomes low

🔄 Supersession & Cross Reference

OEM Supersession Chain

• 1666-8833T16 orders and is serviced by 1666-8833T15
• Related earlier assembly suffixes include 8833A3, 8833A8, 8833A10 and 8833A15 within the same small-gearcase family
• Earlier A-suffix units must be matched by shaft length, shift system and serial number

OEM / Related Numbers

• 1666-8833T15
• 1666-8833T16
• 8833A15
• Related short-shaft gearcase in the 8833 family
• Related propeller-shaft seal carrier, water-pump kit, driveshaft and shift shaft

Aftermarket / Verified Equivalents

• No verified branded direct aftermarket complete unit for every 6HP-15HP Mercury configuration
• Specialist remanufactured Mercury small-outboard lower units are functional alternatives when the 20-inch shaft, 2.00:1 ratio and shift system match
• Sierra, Mallory, GLM and Mercury aftermarket seal, bearing and water-pump kits are available separately

📦 Condition

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