Mercury 50 / 60, 40 / 50 / 60 BigFoot and 40 Jet EFI FourStroke (4 cylinder 995 cc, serial 1C050252 to 1C453839) service guide

Quick answers

How much oil does a Mercury 50 / 60, 40 / 50 / 60 BigFoot and 40 Jet EFI FourStroke take?

3.0 L (3.0 qt) with oil filter replacement.

What engine oil does a Mercury 50 / 60, 40 / 50 / 60 BigFoot and 40 Jet EFI FourStroke use?

NMMA FC-W certified synthetic blend SAE 25W-40 outboard oil for all temperatures; NMMA FC-W certified SAE 10W-30 outboard oil as the alternate viscosity below 4 °C (40 °F).

What gear oil does a Mercury 50 / 60, 40 / 50 / 60 BigFoot and 40 Jet EFI FourStroke use, and how much?

High Performance Gear Lubricant. Quantity: Standard 1.83:1 gear case (87.3 mm, 3-7/16 in): approximately 340 ml (11.5 fl oz). BigFoot 2.33:1 gear case (108 mm, 4-1/4 in): approximately 710 ml (24 fl oz).

What spark plug does a Mercury 50 / 60, 40 / 50 / 60 BigFoot and 40 Jet EFI FourStroke use?

Champion RA8HC, qty 4 (hex 16 mm, 12 mm thread). Gap: 1.0 mm (0.040 in).

How often should a Mercury 50 / 60, 40 / 50 / 60 BigFoot and 40 Jet EFI FourStroke be serviced?

The factory schedule lists: Jet models, every 30 hours of use; Every 100 hours of use or once yearly, whichever occurs first; Every 300 hours of use or three years; Every 400 hours. In Hawaiʻi's salt water we do a full yearly service every 200 hours or 1 year, whichever comes first, and a new engine needs its first (break-in) service.

When should the water pump impeller be replaced on a Mercury 50 / 60, 40 / 50 / 60 BigFoot and 40 Jet EFI FourStroke?

The factory schedule says to replace it at 300 hours. In Hawaiʻi's warm salt water we replace it every 200 hours or 1 year, whichever comes first, because a worn impeller is the most common cause of overheating.

What is the idle speed of a Mercury 50 / 60, 40 / 50 / 60 BigFoot and 40 Jet EFI FourStroke?

725 ± 25 rpm warm, in neutral and in forward gear. WOT range 5500 to 6000 rpm.

What is the propeller nut torque on a Mercury 50 / 60, 40 / 50 / 60 BigFoot and 40 Jet EFI FourStroke?

75 Nm (55 lb-ft); bend the retainer tabs against the nut.

Maintenance specs

Engine oil	NMMA FC-W certified synthetic blend SAE 25W-40 outboard oil for all temperatures; NMMA FC-W certified SAE 10W-30 outboard oil as the alternate viscosity below 4 °C (40 °F)
Engine oil quantity	3.0 L (3.0 qt) with oil filter replacement
Oil filter	Apply a film of clean oil to the gasket (no grease); screw on until the gasket contacts the base, then tighten 3/4 to 1 turn.
Engine oil drain plug	24 Nm (17.5 lb-ft), with grommet; lubricate the seal on the drain plug with oil
Gear lube	High Performance Gear Lubricant
Gear lube quantity	Standard 1.83:1 gear case (87.3 mm, 3-7/16 in): approximately 340 ml (11.5 fl oz). BigFoot 2.33:1 gear case (108 mm, 4-1/4 in): approximately 710 ml (24 fl oz)
Gear lube fill/drain and vent plugs	Standard gear case: 1 vent plug and 1 fill/drain plug, each with a sealing washer; parts list drain plug 6.5 Nm (58 lb-in) with 2 seals, vent screw 6.8 Nm (60 lb-in). BigFoot gear case: 3 drain screws (fill/drain, front vent, rear vent), 3 sealing washers, 7 Nm (60 lb-in). Install new sealing washers
Gear case leak test pressure	69 to 83 kPa (10 to 12 psi) for five minutes, both gear cases
Spark plug	Champion RA8HC, qty 4 (hex 16 mm, 12 mm thread)
Spark plug gap	1.0 mm (0.040 in)
Idle speed	725 ± 25 rpm warm, in neutral and in forward gear. WOT range 5500 to 6000 rpm
Thermostat	Starts to open at 48 to 51 °C (118 to 123 °F); minimum valve lift above 63 °C (145 °F) 3 mm (0.12 in)
Engine fuel filter	Sight bowl filter: check for water or sediment, drain the bowl, and replace the filter assembly if the element is contaminated.
Anodes	One anode on the bottom of the transom bracket and anodes on the gear case. Standard gear case: anode bolt (M6 x 55) 7 Nm (60 lb-in). BigFoot: side anode screw (M6 x 40) 7 Nm (60 lb-in). Trim tab retaining screw 30 Nm (22 lb-ft)
Propeller nut	75 Nm (55 lb-ft); bend the retainer tabs against the nut
Power trim fluid	Power Trim and Steering Fluid, or automotive automatic transmission fluid (ATF) if not available. Tilt full up on the tilt support lock; level even with the bottom of the fill hole
Valve clearance, cold	Intake 0.15 to 0.25 mm (0.006 to 0.010 in); exhaust 0.25 to 0.35 mm (0.010 to 0.014 in)
Timing belt	Inspected every 100 hours. Replace if it has cracks in the back or at the base of the teeth, worn cog roots, oil swelling, roughened surfaces, edge wear, or stretches 10 mm (0.39 in) or more when pushed in with a finger

Service schedule

The factory maintenance intervals, with what is replaced and what is checked at each. Rows marked Hawaiʻi are our shop's yearly service for salt water use.

1. Jet models, every 30 hours of use

   Replace: gear case plug gaskets

2. Every 100 hours of use or once yearly, whichever occurs first

   Replace: engine oil, oil filter, oil drain plug gasket, spark plugs, gear case oil, gear case plug gaskets

   Check: fuel filter, thermostat, anodes

3. Every 200 hours or 1 year (our Hawai‘i yearly service) Hawai‘i

   Replace: engine oil, oil filter, oil drain plug gasket, gear case oil, gear case plug gaskets, water pump impeller

   Check: spark plugs, fuel filter, thermostat, anodes

4. Every 300 hours of use or three years

   Replace: engine oil, oil filter, oil drain plug gasket, gear case oil, gear case plug gaskets, water pump impeller

   Check: spark plugs, fuel filter, thermostat, anodes

5. Every 400 hours

   Replace: engine oil, oil filter, oil drain plug gasket, gear case oil, gear case plug gaskets, water pump impeller

   Check: spark plugs, fuel filter, thermostat, anodes

We replace the water pump impeller at every service from 200 hours up, which can be sooner than the factory schedule, because of Hawaiʻi’s warm salt water.

Source: Mercury 50/60, 40/50/60 BigFoot, 40 Jet EFI FourStroke 4 cyl. service manual, 90-899975. Specs can change by model year and serial number, so always confirm your exact model from the serial tag on the clamp bracket.