Lower Unit Gearcase Seal Kit Compatible With 1994-2005 Mercury 25Hp 30Hp 40Hp 2-Cyl 3-Cyl 2-Stroke

FORCE / MERCURY / MARINER 25-50HP NON-BIGFOOT LOWER UNIT GEARCASE SEAL KIT — Current 823547A03 Supersession Service Kit:

OEM SUPERSESSION CONTEXT:
• 823547A03 is the CURRENT Mercury OEM Supersession
• Replaces Earlier 823547A1 and 823547A2 Part Numbers
• Supersession Chain: 823547A1 → 823547A2 → 823547A03
• Same Applications as Earlier Supersession Part Numbers

KEY TECHNICAL SPECIFICATIONS:
• Gearcase Torpedo Diameter: 3.44" (135mm)
• Gear Ratios Compatible: 1.83:1 AND 2:1
• Lower Unit Type: NON-BIGFOOT (Smaller Torpedo Architecture)
• Per Offshore Marine Authoritative Specification
• ⚠️ Two Different Seal Kits Exist for These HP Ranges — Differentiated by Gear Ratio

CHRYSLER / FORCE APPLICATIONS:
• Force 40HP 2-Cyl 3.375" Bore Outboard 2-Stroke (1995-1999)
• Force 50HP 2-Cyl 3.375" Bore Outboard 2-Stroke (1995-1999)
• Force 40HP / 50HP Top Guided Variants (1996-1999)

MERCURY APPLICATIONS (NON-BIGFOOT):
• Mercury 25HP 2-Cyl 4-Stroke Outboard (1998-2001)
• Mercury 30HP 2-Cyl 2.992" Bore Outboard (1994-2001)
• Mercury 40HP 2-Cyl 2.992" Bore Outboard (1994-2001)
• Mercury 30HP 3-Cyl 4-Stroke Outboard (1999-2001)
• Mercury 30HP 3-Cyl Jet Outboard (1997-2001)
• Mercury 40HP 3-Cyl Outboard (1997-2005)
• Mercury 40HP 3-Cyl 4-Stroke Outboard (1999-2001)
• Mercury 50HP 3-Cyl 2.992" Bore Outboard (1998-2014)
• Mercury 40HP / 45HP / 50HP 4-Cyl 4-Stroke NON-Bigfoot (1995-2001)

MARINER APPLICATIONS:
• All Mariner 25-50HP NON-Bigfoot Models (Rebadged Mercury Engines)
• Same Year / Cylinder / Type Coverage as Mercury
• Mariner 25HP / 30HP / 40HP / 45HP / 50HP NON-Bigfoot Variants

⚠️ NOT COMPATIBLE WITH:
• Mercury BIGFOOT 50HP 4-Cyl 4-Stroke Lower Unit (Use 26-43035A4 — 4.25" Torpedo)
• Mercury 60-125HP Outboards (Different Lower Unit Platform)
• Mercury V6 / V8 Outboards (Different Lower Unit)
• Mercury 18-25HP Older Outboards (Use 26-85090A1 — Different Kit)
• Different Gear Ratio Variant (This Kit is 1.83:1 / 2:1 Only)
• Different Torpedo Diameter (This Kit is 3.44" / 135mm Only)
• 2-Stroke Force 75-120HP (Use 26-43035A4 — Different Kit)
• MerCruiser Sterndrive Applications
• Yamaha / Honda / Suzuki / Tohatsu Outboards (Different Brands)

SPECIFICATIONS:
• Type: Lower Unit Gearcase Seal Kit (Comprehensive)
• Application: Force 40-50HP + Mercury/Mariner 25-50HP NON-BIGFOOT
• Lower Unit Type: NON-BIGFOOT (Smaller Lower Unit Architecture)
• Gearcase Torpedo Diameter: 3.44" (135mm)
• Gear Ratios: 1.83:1 and 2:1
• HP Range: 25 HP through 50 HP
• Engine Configurations: 2-Cyl, 3-Cyl, 4-Cyl
• Engine Types: 2-Stroke and 4-Stroke
• Year Coverage: 1994-2014 (varies by application)
• Includes: Multiple Seals, O-Rings, Gaskets, Drain Plug Gasket
• Material: Marine-Grade Rubber Compounds
• Function: Complete Lower Unit Seal Replacement
• Condition: New

OEM PART NUMBERS:
• Mercury: 823547A03 (Current OEM — Primary)
• Mercury: 26-823547A03 (With 26- Prefix)
• Mercury: 823547A2 (Earlier Supersession)
• Mercury: 26-823547A2 (With 26- Prefix)
• Mercury: 823547A1 (Earliest OEM)
• Mercury: 26-823547A1 (With 26- Prefix)

OEM SUPERSESSION CHAIN (Mercury):
• 26-823547A1 → 26-823547A2 → 823547A03 (CURRENT OEM)

KIT CONTENTS:
• Lower Unit Gearcase Seals
• Multiple O-Rings (Various Sizes / Positions)
• Oil Seals (Prop Shaft and Drive Shaft Positions)
• Drain Plug Gasket
• Other Required Gaskets for NON-Bigfoot 3.44" Torpedo Lower Unit

WHEN TO USE THIS KIT:
• Lower Unit Complete Rebuild
• Annual Lower Unit Service Interval
• Water in Gear Oil (White / Milky Appearance)
• Gear Oil Leaking from Prop Shaft Area
• Gear Oil Leaking from Drive Shaft Area
• Replacing Forward / Reverse Gear Thrust Bearings
• Replacing Prop Shaft Bearings
• Drive Shaft Service
• Routine Preventive Maintenance for NON-Bigfoot Lower Unit

SYMPTOMS REQUIRING SEAL KIT REPLACEMENT:
• Milky / White Gear Oil at Service Drain (Water Contamination)
• Gear Oil Leaking from Prop Shaft Area
• Gear Oil Leaking from Drive Shaft Area
• Failed Pressure Test During Routine Service
• Lower Unit Running Hot
• Cloudy / Discolored Gear Oil
• Loss of Lubrication
• Routine Annual Service Interval Reached

INSTALLATION:
• Step 1: Drain old gear oil completely (note color / condition)
• Step 2: Remove lower unit from outboard
• Step 3: Take photos and notes of disassembly order / orientation
• Step 4: Disassemble gearcase per Mercury / Force service manual
• Step 5: Remove all old seals, gaskets, o-rings
• Step 6: Clean all sealing surfaces thoroughly
• Step 7: Inspect gearcase housing for damage or corrosion
• Step 8: Install new seals with proper orientation (lip direction critical)
• Step 9: Install new gaskets and o-rings with light marine grease
• Step 10: Reassemble gearcase per service manual torque specs
• Step 11: Pressure test gearcase before reinstalling lower unit
• Step 12: Reinstall lower unit to outboard
• Step 13: Refill with proper Mercury Hi-Performance Gear Lubricant
• Step 14: Test forward and reverse operation

⚠️ CRITICAL — VERIFY TORPEDO DIAMETER AND GEAR RATIO:
• This Kit: 3.44" (135mm) Torpedo Diameter + 1.83:1 or 2:1 Gear Ratio
• Bigfoot Uses: 4.25" Torpedo Diameter (Different Kit: 26-43035A4)
• Verify Your Specific Torpedo Diameter AND Gear Ratio Before Ordering
• Two Seal Kits Exist for These HP Ranges Differentiated by Gear Ratio

NOTE: Verify your OEM part number 823547A03 / 823547A2 / 823547A1 AND verify your torpedo diameter is 3.44" (135mm) AND your gear ratio is 1.83:1 or 2:1 before ordering. ***This kit fits ONLY Force 40-50HP outboards AND Mercury/Mariner 25-50HP NON-BIGFOOT outboards with 3.44" torpedo and 1.83:1 or 2:1 gear ratio.*** Bigfoot lower units use different kit (26-43035A4 — 4.25" torpedo). 823547A03 supersedes earlier 823547A1 and 823547A2 part numbers — same applications. Replace all seals concurrently for proper lower unit longevity.