Mercury 30 / 40 EFI FourStroke (3 cylinder, 747 cc) service guide

Quick answers

How much oil does a Mercury 30 / 40 EFI FourStroke take?

3 L (3 US qt) with filter.

What engine oil does a Mercury 30 / 40 EFI FourStroke use?

NMMA FC-W synthetic blend SAE 25W-40 all temperatures; FC-W 10W-30 below 4 °C (40 °F).

What gear oil does a Mercury 30 / 40 EFI FourStroke use, and how much?

High Performance Gear Lubricant only. Quantity: About 440 ml (15 fl oz); 2:1 ratio.

What spark plug does a Mercury 30 / 40 EFI FourStroke use?

NGK DPR6EA-9, 18 mm hex, qty 3.

How often should a Mercury 30 / 40 EFI FourStroke be serviced?

The factory schedule lists: Every 100 hours or once a year; Every 300 hours or 3 years. 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 30 / 40 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 30 / 40 EFI FourStroke?

In gear 750 to 800 r/min; warm idle 750 ± 25 r/min; set by the ECM.

What is the propeller nut torque on a Mercury 30 / 40 EFI FourStroke?

75 N·m (55.3 lb·ft); bend the retainer tabs.

Maintenance specs

Engine oil	NMMA FC-W synthetic blend SAE 25W-40 all temperatures; FC-W 10W-30 below 4 °C (40 °F)
Engine oil quantity	3 L (3 US qt) with filter
Oil drain plug (driveshaft housing)	24 N·m (17.5 lb·ft)
Gear lubricant	High Performance Gear Lubricant only
Gearcase capacity	About 440 ml (15 fl oz); 2:1 ratio
Gearcase plugs	Drain plug 6.5 N·m (58 lb·in); vent screw 6.8 N·m (60 lb·in)
Gearcase leak test	69 to 83 kPa (10 to 12 psi); 5 minutes, 15 minutes
Spark plug	NGK DPR6EA-9, 18 mm hex, qty 3
Spark plug torque	17 N·m (150 lb·in), or finger tight then 1/4 turn
Idle speed	In gear 750 to 800 r/min; warm idle 750 ± 25 r/min; set by the ECM
Thermostat	Starts to open 48 to 51 °C (118 to 123 °F); lift at least 3 mm (0.12 in) above 63 °C (145 °F)
Water pressure	800 r/min 7 to 21 kPa (1 to 3 psi); 6000 r/min 83 to 172 kPa (12 to 25 psi); measure warm
Anodes	Trim tab screw 30 N·m (22 lb·ft); gearcase side anodes (108 mm gearcase) M6 x 55 bolt 7 N·m (62 lb·in); transom bracket anode M6 x 25 bolts 6.8 N·m (60 lb·in), 6 N·m (53 lb·in)
Propeller nut	75 N·m (55.3 lb·ft); bend the retainer tabs
Power trim fluid	Power Trim and Steering Fluid or ATF Dexron III, to the bottom of the fill hole
Valve clearance, cold	IN 0.15 to 0.25 mm (0.006 to 0.010 in); EX 0.25 to 0.35 mm (0.010 to 0.014 in); locknut 13.5 N·m (120 lb·in)
Timing belt	Inspect every 100 h / yearly; replace if cracked, worn, oily, or it deflects 10 mm (0.39 in) or more when pushed 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. Every 100 hours or once a year

   Replace: engine oil, oil filter, oil drain plug gasket, 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: fuel filter, thermostat, anodes

3. Every 300 hours or 3 years

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

   Check: 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 30/40 EFI 3 Cylinder FourStroke service manual, 90-8M0105569. Specs can change by model year and serial number, so always confirm your exact model from the serial tag on the clamp bracket.