300 Hour Service Kit – Fits Mercury 250-300HP V8 4.6L Engines (Replaces 8M0149931, 8M0149932)
300 Hour Service Kit – Fits Mercury 250-300HP V8 4.6L Engines (Replaces 8M0149931, 8M0149932) is backordered and will ship as soon as it is back in stock.
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Worry-free returns
Worry-free returns
You may return most new, unopened items within 7 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received an incorrect or defective item, etc.).
You should expect to receive your refund within four weeks of giving your package to the return shipper, however, in many cases you will receive a refund more quickly. This time period includes the transit time for us to receive your return from the shipper (5 to 10 business days), the time it takes us to process your return once we receive it (3 to 5 business days), and the time it takes your bank to process our refund request (5 to 10 business days).
If you need to return an item, simply login to your account, view the order using the "Complete Orders" link under the My Account menu and click the Return Item(s) button. We'll notify you via e-mail of your refund once we've received and processed the returned item.
Delivery and Shipping
Delivery and Shipping
Free standard shipping on all orders under 1 KG
Product Details
This 300 Hour Service Kit – Fits Mercury 250-300HP V8 4.6L Engines provides all the essential components for the 300-hour maintenance interval on Mercury Marine 250-300 HP, V8 4.6L four-stroke outboard engines. It is engineered to meet manufacturer specifications for a complete service.
This kit is a direct replacement for Mercury OEM part numbers 8M0149931 and 8M0149932.
- Engineered for direct OEM replacement installation.
- Includes an extra quart of engine oil for routine top-offs between services.
- Formulated for gasoline-powered four-stroke marine engines.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| Mercury | 8M0149931 |
| Mercury | 8M0149932 |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For Mercury Marine engines, this kit is specifically designed for the V8 4.6L models listed. Please verify your engine's horsepower and model to ensure correct fitment.
| Brand | Model | Rated HP | Stroke | OEM Part No. | Notes |
|---|---|---|---|---|---|
| Mercury | V8 4.6L | 250 | 4-Stroke | 8M0149931, 8M0149932 | - |
| Mercury | V8 4.6L | 300 | 4-Stroke | 8M0149931, 8M0149932 | - |
| Mercury | V8 4.6L | 300R | 4-Stroke | 8M0149931, 8M0149932 | - |
| Mercury | V8 4.6L | 300R HD | 4-Stroke | 8M0149931, 8M0149932 | - |
Technical Specs
- Product Type
- Service/Maintenance Kit
- Installation
- Direct OEM Replacement
- Fuel Type
- Gasoline
- Oil Type
- 10W-30 4-Stroke Marine Engine Oil
- Oil Specifications
- API SM/NMMA FC-W®
- Engine Oil Capacity
- 8 liters/8.5 quarts
- Gear Oil Type
- High Performance Gear Oil (85W-90)
- Gear Oil Capacity
- 720/680 or 980 ml (SeaPro models)
- Dimensions
- 16.5" H x 32.2" W x 22.3" L
What’s in the Box
- 1 x OEM Oil Filter
- 2 x OEM Lower Unit Drain Plug Seals
- 8 x Liters of Liqui Moly Marine Engine Oil (10W-30)
- 1 x Liter of Liqui Moly Marine High Performance Gear Oil (85W-90)
Installation Notes
- Ensure the engine is turned off and has cooled down before beginning service.
- Position a drain pan under the lower unit and engine oil drain plug.
- Remove the oil fill cap to vent the system, then remove the drain plug to drain the old engine oil.
- Remove and replace the old oil filter, applying a light coat of new oil to the gasket of the new filter.
- Reinstall the engine oil drain plug with a new seal and torque to the manufacturer's specification.
- Refill the engine with the specified amount of new 10W-30 engine oil. Do not overfill.
- Remove the upper (vent) and lower (fill) drain plugs on the gearcase to drain the old gear oil.
- Pump new 85W-90 gear oil into the lower hole until it flows out of the upper vent hole.
- Reinstall the upper vent plug, then the lower fill plug, both with new seals.
- Check all fluid levels and inspect for leaks after running the engine briefly.
Troubleshooting & FAQ
Which specific Mercury engines does this kit fit?
This kit is designed exclusively for Mercury Marine 250 HP, 300 HP, 300R, and 300R HD V8 4.6L four-stroke outboard engines. Always verify your engine model before ordering.
What is the difference between this kit and the OEM Mercury kits (8M0149931, 8M0149932)?
Our kit is an aftermarket solution designed to provide the same components and fluid specifications required for the 300-hour service. It includes high-quality Liqui Moly oils that meet API SM/NMMA FC-W® standards, just like the OEM kit.
How often should I perform this 300-hour service?
This service should be performed every 300 hours of operation or every three years, whichever comes first, as recommended by the manufacturer. Regular service is crucial for engine longevity and performance.
What are the signs my engine needs this service?
Besides tracking engine hours, signs include reduced performance, increased fuel consumption, or dark, gritty oil on the dipstick. Sticking to the recommended service interval is the best way to prevent issues.
Does this kit work for SeaPro models?
Yes, this kit is compatible with V8 4.6L SeaPro models. Note the different gear oil capacity (980 ml) for these specific engines when refilling the lower unit.
Is everything I need for the service included?
This kit contains the essential fluids, filter, and drain plug seals for the 300-hour service. You will still need basic tools, a drain pan, and a gear lube pump.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns?
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
Payment & Security
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