677-45113-A0 Power Head Base Gasket for Yamaha Mariner 6B 8B | JLM Marine

Power Head Base Gasket – Fits Yamaha Mariner 6B 8B 2-Stroke Outboards

This aftermarket powerhead base gasket is precision-engineered for Yamaha Mariner 6 HP and 8 HP 2-stroke outboard models (6B, 8B). Designed specifically for units with serial numbers starting with 677, this gasket ensures a reliable seal between the powerhead and block, critical for maintaining compression and preventing oil/fuel leaks.

Direct replacement for OEM part numbers: 677-45113-A0, 677-45113-A1. Compatible with older Japan-manufactured Mariner models under the Yamaha platform.

• Includes one complete powerhead base gasket
• Designed for 2-stroke 6 HP and 8 HP Yamaha Mariner outboards
• Fits only older Mariner Japan models with serial numbers starting with 677

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Yamaha owners, here's a guide to help you identify your engine's serial/model: Yamaha Serial Number Guide. You can also review exploded diagrams to verify part numbers: Yamaha Parts Diagrams & Catalog.

Technical Specifications

Package Contents

Your package includes:

• 1 × Outboard Power Head Base Gasket

Installation Guide

1. Disconnect the fuel line and remove the spark plug wire to prevent accidental starting during service.
2. Remove the powerhead mounting bolts and carefully lift the powerhead assembly off the engine block.
3. Thoroughly clean all mating surfaces on both the powerhead and the block, removing all old gasket material and residue. Use a gasket scraper and solvent; ensure surfaces are dry before proceeding.
4. Inspect both surfaces for warping, cracks, or damage. Address any irregularities before installing the new gasket.
5. Position the new powerhead base gasket onto the engine block, aligning all bolt holes and ports precisely.
6. Carefully lower the powerhead back onto the gasket, ensuring it seats evenly without shifting the gasket.
7. Install all mounting bolts hand-tight first, then torque them to manufacturer specifications in a cross-pattern sequence to ensure even compression.
8. Reconnect the spark plug wire and fuel line, then perform a visual inspection for proper alignment and seating.
9. Start the engine and let it reach operating temperature. Check for oil or fuel leaks around the gasket perimeter; retorque bolts if necessary after the first run.

Troubleshooting & FAQ

How do I confirm this gasket fits my Yamaha Mariner engine?
Verify that your engine is a 6 HP or 8 HP 2-stroke model (6B or 8B) and that the serial number starts with 677. This gasket fits only older Japan-manufactured Mariner models; cross-check your existing OEM part number (677-45113-A0 or 677-45113-A1) to confirm compatibility.

What are the symptoms of a failing powerhead base gasket?
Common signs include oil or fuel seepage around the powerhead base, loss of compression, rough idle, or difficulty starting. If you notice wet residue or strong fuel odor near the powerhead-to-block joint, inspect and replace the gasket promptly.

How often should I replace the powerhead base gasket?
Replace the gasket any time the powerhead is removed for service or repair. Gaskets are one-time-use components and should not be reused, as they compress and conform to mating surfaces during initial installation.

Can I reuse the old gasket if it looks intact?
No. Even if the old gasket appears undamaged, it has already compressed and conformed to the engine surfaces. Reusing it will likely result in leaks and poor sealing, compromising engine performance and reliability.

What is the difference between this aftermarket gasket and the OEM version?
This aftermarket gasket is manufactured to OEM specifications using comparable materials and production standards. It provides the same fit and sealing performance as the original Yamaha part, but at a more competitive price point.

Is this an OEM part or aftermarket?
This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

How fast do you ship and how much does it cost?
We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

What is your warranty and return policy?
This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.