8M0090559 Maintenance Kit for Mercury 40HP 50HP 60HP EFI 4-Stroke BigFoot CT | JLM Marine

8M0090559 Maintenance Kit for Mercury 40HP 50HP 60HP EFI 4-Stroke BigFoot CT

This comprehensive maintenance kit is specifically designed for Mercury 40HP, 50HP, and 60HP EFI 4-Cylinder 4-Stroke outboard motors equipped with BigFoot and CT gearcases. It consolidates all essential service components into one package, ensuring your engine receives complete care during routine maintenance intervals.

This kit directly replaces Mercury OEM maintenance kit 8M0090559, providing a complete solution for water pump repair, cooling system service, and filtration replacement in a single purchase.

• Includes water pump repair kit, thermostat assembly, fuel filters (both high and low pressure), oil filter, and drain gaskets
• Designed specifically for EFI 4-cylinder models with BigFoot and CT gearcase configurations
• Streamlines maintenance by bundling all critical service components together

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 Mercury owners, here's a guide to help you identify your engine's serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

This maintenance kit includes the following components:

• 1 × Water Pump Repair Kit (47-8M0100527)
• 1 × Cotter Pin (951403-0310)
• 1 × Thermostat (8M0168892)
• 1 × Thermostat Gasket (27-887978 & 27-8M0177107)
• 1 × Fuel Filter Assembly (low pressure) (35-879884T)
• 1 × Fuel Filter (high pressure) (35-8M0153652)
• 1 × Oil Filter (35-8M0162829)
• 1+3 Drain Gaskets (26-8M0007119 & 26-8M0204693)

Important: This kit is designed exclusively for BigFoot and CT gearcase models. Verify your gearcase type before ordering.

Installation Guide

1. Preparation: Gather necessary tools including socket set, screwdrivers, torque wrench, and drain pan. Ensure the engine is cool and in an upright position.
2. Oil Filter Replacement: Locate the oil filter on the engine block, remove the old filter, and install the new oil filter from the kit. Tighten securely by hand.
3. Drain Plug Service: Remove the engine oil drain plug and gearcase drain/fill plugs. Replace drain plug gaskets with the new gaskets provided in the kit.
4. Fuel Filter Replacement: Replace both the low-pressure fuel filter assembly and high-pressure fuel filter. Ensure fuel line connections are secure and free from leaks.
5. Water Pump Service: Remove the lower unit to access the water pump housing. Disassemble the old water pump components.
6. Water Pump Installation: Install the new impeller, gaskets, seals, and O-rings from the water pump repair kit following the proper orientation. Lubricate components with glycerin or soapy water.
7. Thermostat Replacement: Locate the thermostat housing on the cylinder head and remove the cover. Replace the old thermostat and gasket with the new components from the kit.
8. Reassembly: Reinstall the lower unit, ensuring all bolts are torqued to manufacturer specifications. Reconnect all fuel lines and verify proper routing.
9. Fluid Refill: Refill engine oil and gearcase lubricant to the proper levels using manufacturer-recommended fluids. Check for leaks around all service points.
10. System Check: Start the engine and verify water pump discharge (telltale stream). Check for fuel leaks, oil leaks, and proper operating temperature.
11. Test Run: Run the engine at idle and then at varying RPMs to ensure all systems operate correctly. Monitor temperature gauge and watch for any abnormal sounds or leaks.
12. Final Inspection: After the test run, recheck all fluid levels and inspect all service areas for leaks. Dispose of used oil, filters, and fluids properly.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my specific Mercury outboard?
A: Verify that your engine is a 40HP, 50HP, or 60HP EFI 4-cylinder 4-stroke model equipped with either a BigFoot or CT gearcase. Standard gearcase models require a different maintenance kit. Check your engine's serial number plate or consult your owner's manual to confirm the gearcase type.

Q: How often should I perform this maintenance service?
A: Mercury recommends performing comprehensive maintenance every 100 hours of operation or annually, whichever comes first. In harsh conditions (saltwater, heavy use, extreme temperatures), consider more frequent intervals—every 50-75 hours.

Q: Can I install just some components from this kit or do I need to use everything at once?
A: While the kit is designed for complete service intervals, individual components can be replaced as needed. However, performing all maintenance tasks together ensures optimal engine performance and simplifies service scheduling.

Q: What are the signs that my water pump or thermostat needs replacement?
A: Common symptoms include weak or absent telltale stream, engine overheating, steam from the engine cover, reduced performance, or temperature alarms. If you notice any of these signs, inspect and replace the water pump and thermostat immediately.

Q: Does this kit include engine oil and gearcase lubricant?
A: No, this kit includes the oil filter and drain gaskets but does not include the actual engine oil or gearcase lubricant. Purchase the appropriate Mercury-recommended fluids separately based on your operating conditions.

Q: Is this an OEM or aftermarket part?
A: 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.

Q: How fast do you ship and how much does it cost?
A: 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.

Q: What is your warranty and return policy?
A: 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.