Mercury & Mariner 1987-2006 3-Cylinder 2-Stroke 70-90 HP Outboard Powerhead Parts Diagrams

Explore our comprehensive parts collection for Mercury and Mariner 3-cylinder powerheads (70–90 HP) from 1987 to 2006. This page offers OEM-quality components and reliable aftermarket alternatives, complete with clear diagrams for seamless identification. Shop essential parts, including: 

• Gaskets and complete gasket kits
• Carburetor rebuild kits
• Fuel pump kits (e.g., check valve fuel pump)
• Crankshaft components (upper crank seals, crank bearings, center main bearings)
• Connecting rods and rod bolts
• Wrist pin bearings
• Thermostats and related durable engine parts

Whether you're performing routine maintenance or rebuilding a powerhead, OBParts helps you find the right components quickly and affordably—backed by the diagrams and support you need. Everything is sourced for accuracy and compatibility, from trusted brands like Red Rhino and Pro Marine, offering a mix of affordability and performance.

The following parts correspond to the numbers on this diagram:

1. Thermostat
• 1987-1993 (143°)
• 1988-2003 (120°)
  

We recommend the following kits for this powerhead:

• Gasket Set
• Carburetor Kit
• Fuel Pump Kit
• In-Line Check Valve
• 90° Check Valve

The following diagram is for a Mercury/Mariner Crankshaft Assembly for 3 Cylinder 70-90 HP models from 1987-2006. 

The following parts correspond to the numbers on this diagram:

1. Rod Bearing with Cage
2. Wrist Pin Bearings
• 1987-1991 (Bottom guided, Use w/ rod #638-8532-1)
• 1992-2003 (Top guided, Use w/ rod #646-818846)
3. Lower Main Bearing
4. Rod Bolt
5. Upper Main Bearing
6. Connecting Rod
• Bottom Guided
• Top Guided

Although not numbered on the diagram, the following items are available for purchase:

• Crankshaft Seal Kit
• Center Main Bearing