Mercury 225 FourStroke EFI (2003 on) service guide

Quick answers

How much oil does a Mercury 225 FourStroke EFI take?

5.8 L (6.1 US qt) without oil filter replacement; 6.0 L (6.3 US qt) with oil filter replacement.

What engine oil does a Mercury 225 FourStroke EFI use?

4-cycle marine oil, SAE 10W-30 or 10W-40 for all temperatures; SAE 25W-40 may be used above 4 °C (40 °F). If not available, a premium 4-cycle engine oil API SJ, SH, SG, SF or SE. Oil filter P/N 35-822626T7.

What gear oil does a Mercury 225 FourStroke EFI use, and how much?

Premium Gear Lubricant, API GL-4 or SAE 90. Quantity: Right-hand rotation 1,150 ml (39 fl oz); left-hand rotation 1,000 ml (34 fl oz); fill through the fill/drain hole until it flows out of the vent screw hole with no air bubbles.

What spark plug does a Mercury 225 FourStroke EFI use?

NGK LFR5A-11, qty 6 (16 mm hex, 14 mm hole). Gap: 1.0 to 1.1 mm; the inspection procedure gives 1.1 mm (0.043 in.).

How often should a Mercury 225 FourStroke EFI be serviced?

The factory schedule lists: After first 20 hours (break-in); Every 100 hours or 6 months; Every 300 hours or 3 years; Every 400 hours or 2 years; Every 1,000 hours or 5 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 225 FourStroke EFI?

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 225 FourStroke EFI?

650 to 750 RPM, in neutral, warm.

What is the propeller nut torque on a Mercury 225 FourStroke EFI?

55 N·m (41 lb-ft); new cotter pin, tighten further to align the hole if needed.

Maintenance specs

Engine oil	4-cycle marine oil, SAE 10W-30 or 10W-40 for all temperatures; SAE 25W-40 may be used above 4 °C (40 °F). If not available, a premium 4-cycle engine oil API SJ, SH, SG, SF or SE. Oil filter P/N 35-822626T7
Engine oil quantity	5.8 L (6.1 US qt) without oil filter replacement; 6.0 L (6.3 US qt) with oil filter replacement
Oil filter	18 N·m (159 lb-in); clean oil on the gasket, no grease; oil filter wrench 91-889277002
Engine oil drain plug (M14)	27 N·m (20 lb-ft); remove the starboard apron (seven screws) to reach it, apron screw 8 N·m (71 lb-in)
Gear lube	Premium Gear Lubricant, API GL-4 or SAE 90
Gear lube quantity	Right-hand rotation 1,150 ml (39 fl oz); left-hand rotation 1,000 ml (34 fl oz); fill through the fill/drain hole until it flows out of the vent screw hole with no air bubbles
Gear lube fill/drain plug and vent plug	One fill/drain plug (magnetic) and one vent plug, each with a sealing washer: the parts list shows drain plug qty 1, plug qty 1, gasket qty 2. Install the vent plug before removing the lubricant tube, then the fill/drain plug and sealing washer
Gearcase pressure check	Must hold 10 to 12 psi for five minutes without leaking down, with no lubricant in the gearcase
Spark plug	NGK LFR5A-11, qty 6 (16 mm hex, 14 mm hole)
Spark plug gap	1.0 to 1.1 mm; the inspection procedure gives 1.1 mm (0.043 in.)
Spark plug torque	25 N·m (18.5 lb-ft)
Idle speed	650 to 750 RPM, in neutral, warm
Thermostat (qty 2)	Opens at 60 °C (140 °F); fully open at 70 °C (158 °F); valve lift minimum 4.3 mm (0.17 in.)
Anodes	Trim tab (gear housing anode) screw 43 N·m (32 lb-ft); transom bracket anode screw 8 N·m (71 lb-in); four anodes in the engine block: anode screw 8 N·m (71 lb-in), anode cover screw 17 N·m (150 lb-in). Replace an anode before it is 50% eroded
Propeller nut	55 N·m (41 lb-ft); new cotter pin, tighten further to align the hole if needed
Power trim fluid	Power Trim and Steering Fluid, or Dexron II ATF if not available; fill until it overflows out of the filler hole. Reservoir cap (M12) 7 N·m (62 lb-in)
Valve clearance, cold	Intake 0.20 ± 0.03 mm (0.008 ± 0.001 in.); exhaust 0.34 ± 0.03 mm (0.013 ± 0.001 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. After first 20 hours (break-in)

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

   Check: spark plugs, fuel filter

2. Every 100 hours or 6 months

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

   Check: spark plugs, 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 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

5. Every 400 hours or 2 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

6. Every 1,000 hours or 5 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

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 225 FourStroke EFI service manual, 90-8M0047913. Specs can change by model year and serial number, so always confirm your exact model from the serial tag on the clamp bracket.