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Mercury 115 EFI FourStroke (2001 to 2006) service guide

Oil, gear oil, spark plugs and the service schedule for the Mercury 115 EFI FourStroke (2001 to 2006) (115 hp, four-stroke), from the factory service manual, plus how we service it in Hawaiʻi.

Models covered: Mercury 115 FourStroke EFI, 4 cylinder, model years 2001 to 2006, serial 0T178500 to 1B366822. The 2.1 L 115 has its own sheet.

Quick answers

What engine oil does a Mercury 115 EFI FourStroke use?
SAE 10W-30 all temperatures; 25W-40 above 4 °C (40 °F).
What gear oil does a Mercury 115 EFI FourStroke use, and how much?
Premium Gear Lubricant. Quantity: 710 ml (24 fl oz).
What spark plug does a Mercury 115 EFI FourStroke use?
NGK LFR6A-11.
How often should a Mercury 115 EFI FourStroke be serviced?
The factory schedule lists: Every 100 hours or once a year; Every 300 hours or 3 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 115 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 115 EFI FourStroke?
Neutral 750 ± 50 r/min; forward 700 ± 50 r/min.
What is the propeller nut torque on a Mercury 115 EFI FourStroke?
75 N·m (55 lb·ft); bend three tabs.

Maintenance specs

Engine oilSAE 10W-30 all temperatures; 25W-40 above 4 °C (40 °F)
Oil filter3/4 to 1 turn after the gasket touches
Oil drain plug24 N·m (17.5 lb·ft)
Gear lubricantPremium Gear Lubricant
Gearcase capacity710 ml (24 fl oz)
Gearcase drain and vent screwsDrain screw 7 N·m (60 lb·in); vent screw 6.7 N·m (60 lb·in)
Gearcase leak test69 to 83 kPa (10 to 12 psi) for 5 minutes
Spark plugNGK LFR6A-11
Spark plug torque25 N·m (18 lb·ft), or finger tight then 1/4 turn
Idle speed, warmNeutral 750 ± 50 r/min; forward 700 ± 50 r/min
ThermostatOpens 50 °C (122 °F); fully open 60 °C (140 °F); lift at least 4.3 mm (0.17 in).
Water pressureIdle (750 r/min) 14 to 48 kPa (2 to 7 psi); WOT (5500 r/min) 41 to 138 kPa (6 to 20 psi)
Propeller nut75 N·m (55 lb·ft); bend three tabs
Valve clearance, coldIN 0.17 to 0.23 mm (0.007 to 0.009 in); EX 0.31 to 0.37 mm (0.012 to 0.014 in)

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. Every 100 hours or once a year

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

    Check: fuel filter, thermostat, anodes

  2. 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

  3. Every 300 hours or 3 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

  4. 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 115 FourStroke EFI service manual, 90-881980R03. Specs can change by model year and serial number, so always confirm your exact model from the serial tag on the clamp bracket.

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