1. Technical Specifications

2. Key Features

• Marine-Grade Alloy Construction: Precision cast from high-strength corrosion-resistant aluminum alloy with protective coatings to withstand harsh marine, saltwater, and high-humidity environments.

• High-Precision CNC Machining: CNC-machined crankshaft bearing journals and mating surfaces guarantee high concentricity, reducing vibration and mechanical wear.

• Superior Sealing & Structural Rigidity: Reinforced crankcase structure endures intense combustion pressures and thermal shock while maintaining optimal primary crankcase compression.

• Precise OEM Fitment: Mounting holes, dowel pin locations, and passage ports strictly follow factory specifications for seamless installation of oil seals, bearings, and reed valves.

3. Compatible Models

Designed primarily for Yamaha 40 HP to 50 HP 2-stroke outboard motor platforms (always verify using your engine serial number or OEM part manual):

• Primary OEM Fitment:

• Yamaha 2-Stroke: 40HP / 50HP series (e.g., 40J, 40N, 50J, 50N, E40J, E50J 2-cylinder/3-cylinder 2-stroke models)

• Extended Application: Select aftermarket/Chinese 40HP / 50HP 2-stroke outboard models built on the Yamaha 6F5 powerhead architecture.

4. Aftermarket & Brand Compatibility

Due to the exceptional reliability and market saturation of the Yamaha 40HP–50HP 2-stroke architecture, this component platform is widely supported across global marine markets:

• PREMARINE Brand Replacement: As a trusted marine parts and accessories supplier, PREMARINE offers premium aftermarket replacement crankcase assemblies designed to meet or exceed original OEM specifications. PREMARINE units feature high-grade aluminum alloys and marine-spec corrosion protection, serving as a reliable and cost-effective direct-replacement option for 6F5-15100-00.

• Chinese Clone Engines: Marine brands such as Parsun, Hidea, Seapro, and Yamabisi build 40HP–50HP 2-stroke engines directly based on the Yamaha 6F5 platform, making them fully compatible with PREMARINE and OEM 6F5-15100-00 parts.

• Interchangeability: Physical mounting hole dimensions, bearing saddle dimensions, cylinder mating surfaces, and bolt pattern specifications match 6F5-15100 standards for seamless, direct replacement.

5. Common Symptoms & Troubleshooting

• Symptom 1: Crankcase Pressure Leak / Loss of Primary Compression & Power

• Cause: Warped crankcase mating surfaces, corroded sealing lips, or failed sealant causing air/fuel leakage.

• Solution: Inspect joint surface flatness and corrosion. If severely pitted or damaged, replace with a new crankcase assembly and apply fresh marine sealant.

• Symptom 2: Abnormal Crankshaft Noise or Excessive Bearing Play

• Cause: Severe engine seizure or bearing failure damaging the internal bearing saddles of the crankcase.

• Solution: Measure bearing saddle bore dimensions; if out of factory tolerance, replace the crankcase assembly to restore true shaft alignment.

• Symptom 3: Water/Cooling Passage Corrosion or Pitting Holes

• Cause: Severe galvanic corrosion from prolonged saltwater exposure without proper flushing.

• Solution: Replace with a fresh, marine-treated crankcase assembly and inspect anode condition regularly.

OEM Part Numbers

Compatible OEM references include:

6F5-15100-00

6F5-15100-00-00

6F5-15100-01-00

Compatible Engine Models

This Powerhead Crankcase Assembly is primarily designed for:

2-Stroke 40/50HP

It is also widely used in compatible engines based on the Yamaha, including selected models from:

Parsun

Hidea

Seapro

Yamabisi

If you are unsure about compatibility, please provide your engine model number or identification plate for verification before ordering.

Applications

This Powerhead Crankcase Assembly is commonly used for:

Outboard engine repair

Engine rebuilding projects

Marine maintenance workshops

Boat fleet maintenance

Commercial fishing vessels

Recreational boats

Marine spare parts distribution