1671-9760t25 mercury long shaft gearbox | Genuine Used Part

🔧 Product Description

Genuine Mercury / Mariner 40HP-60HP 20-Inch Long-Shaft Gearcase - Part Number: 1671-9760T25

A genuine black complete long-shaft lower unit from the Mercury 9760 three-cylinder two-stroke gearcase family. It was used on selected 40HP, 45HP, 50HP, 55HP and 60HP engines. The same housing family was assembled with model-specific standard and BigFoot gear sets, so the exact ratio must be confirmed before interchange.

⚙️ Key Features

• Genuine Mercury Marine complete gearcase
• Correct part number 1671-9760T25
• 20-inch long-shaft configuration
• Approximately 3.44-inch torpedo housing family
• Standard rotation with model-specific gear ratio

🚤 Compatibility

• Mercury / Mariner 40HP three-cylinder two-stroke
• Mercury / Mariner 45HP, 50HP and 55HP three-cylinder two-stroke
• Mercury / Mariner 60HP three-cylinder two-stroke
• Selected 60HP BigFoot applications using the compatible 1.64:1 gear set
• Documented serial families include USA 0G-series and Belgium 9885345-9973099
• Approximate application era: 1991-2006
• Fitment requires the correct ratio, driveshaft spline and shift-shaft arrangement

🔌 Function

The lower unit reduces engine speed through the bevel gears, provides forward and reverse selection and drives the propeller and cooling-water pump.

⚠️ Common Signs of Failure

• Incorrect ratio causes poor performance
• Gear oil leaks or contains water
• Clutch dogs wear
• Propeller shaft is bent
• Housing or skeg is impact damaged
• Water-pump output becomes weak

🔄 Supersession & Cross Reference

OEM Supersession Chain

• 1671-9760A25 is an earlier assembly superseded by 1671-9760T25
• 1671-9760T23 is the related short-shaft version
• 1671-9760T28 is the related extra-long-shaft version
• The 9760 housing family includes standard and BigFoot gear sets and is not interchangeable solely by casting number

OEM / Related Numbers

• 1671-9760T25
• 1671-9760A25
• 1671-9760T23 short shaft
• 1671-9760T28 extra-long shaft
• Casting family 1671-9760-C
• Related standard and 1.64:1 BigFoot gear sets

Aftermarket / Verified Equivalents

• SEI and specialist remanufactured Mercury 40HP-60HP lower units where supported
• Rebuilt Mercury 9760-family complete units from marine gearcase specialists
• Sierra, GLM, Mallory and Mercury-compatible seal, clutch, bearing and water-pump components

📦 Condition

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