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Mercury 150 FourStroke (3.0 L), 150 SeaPro, 150 Pro XS service guide

Oil, gear oil, spark plugs and the service schedule for the Mercury 150 FourStroke (3.0 L), 150 SeaPro, 150 Pro XS (150 hp, four-stroke), from the factory service manual, plus how we service it in Hawaiʻi.

Models covered: Mercury 150, 150 SeaPro and 150 Pro XS FourStroke, 4 cylinder 3.0 L, serial 1B905505 and above.

Quick answers

How much oil does a Mercury 150 FourStroke, 150 SeaPro, 150 Pro XS take?
6.0 L (6.3 US qt) with filter.
What engine oil does a Mercury 150 FourStroke, 150 SeaPro, 150 Pro XS use?
Standard and Pro XS: NMMA FC-W SAE 10W-30 for all temperatures; 25W-40 allowed above 4 °C (40 °F). SeaPro: 25W-40 recommended; 10W-30 at 0 °C (32 °F) or below.
What gear oil does a Mercury 150 FourStroke, 150 SeaPro, 150 Pro XS use, and how much?
High Performance Gear Lubricant. Quantity: RH, 150 and SeaPro S/N 3B111734 and below: 830 ml (28.1 fl oz). LH S/N 2B172248 and below: 545 ml (18.4 fl oz). LH S/N 2B172249 and above: 830 ml. Pro XS 4.8 in. and SeaPro S/N 3B111735 and above, LH and RH: 970 ml (32.8 fl oz).
What spark plug does a Mercury 150 FourStroke, 150 SeaPro, 150 Pro XS use?
NGK ZFR5F, qty 4, 16 mm hex. Gap: 0.8 mm (0.032 in).
How often should a Mercury 150 FourStroke, 150 SeaPro, 150 Pro XS 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 150 FourStroke, 150 SeaPro, 150 Pro XS?
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 150 FourStroke, 150 SeaPro, 150 Pro XS?
650 ± 50 r/min; idle charge 650 to 800 r/min.
What is the propeller nut torque on a Mercury 150 FourStroke, 150 SeaPro, 150 Pro XS?
75 N·m (55.3 lb·ft); bend the retainer tabs.

Maintenance specs

Engine oilStandard and Pro XS: NMMA FC-W SAE 10W-30 for all temperatures; 25W-40 allowed above 4 °C (40 °F). SeaPro: 25W-40 recommended; 10W-30 at 0 °C (32 °F) or below
Engine oil quantity6.0 L (6.3 US qt) with filter
Oil filterOil the gasket; turn on until the gasket touches, then 3/4 to 1 turn
Oil drain valve15 N·m (132.7 lb·in). Loosen no more than 2 1/2 turns to drain
Gear lubricantHigh Performance Gear Lubricant
Gearcase capacity (approximate)RH, 150 and SeaPro S/N 3B111734 and below: 830 ml (28.1 fl oz). LH S/N 2B172248 and below: 545 ml (18.4 fl oz). LH S/N 2B172249 and above: 830 ml. Pro XS 4.8 in. and SeaPro S/N 3B111735 and above, LH and RH: 970 ml (32.8 fl oz)
Gear housing leak test103.4 kPa (15 psi) for 15 minutes, without lubricant; the Pro XS 4.8 in. and SeaPro 3B111735+ tables say 5 minutes
Spark plugNGK ZFR5F, qty 4, 16 mm hex
Spark plug gap0.8 mm (0.032 in)
Spark plug torque27 N·m (20 lb·ft), or finger tight plus 1/4 turn
Idle speed650 ± 50 r/min; idle charge 650 to 800 r/min
ThermostatStarts to open 46.1 to 51.7 °C (115 to 125 °F); fully open 65.6 °C (150 °F); stroke at least 7.62 mm (0.30 in)
Water pressure5 to 30 kPa (0.7 to 4.4 psi) at 650 r/min idle; 80 to 300 kPa (11.6 to 43.5 psi) at 5800 r/min
Anode screwsTrim tab anode 54 N·m (39.8 lb·ft); gearcase side anodes M6 x 40 6.8 N·m (60.2 lb·in); trim unit base anode M6 x 25 8 N·m (70.8 lb·in)
Propeller nut75 N·m (55.3 lb·ft); bend the retainer tabs
Power trim fluidPower Trim and Steering Fluid, or ATF Type F, FA, Dexron II or III; level with the bottom of the fill hole, tilted full up. Cap 2.5 N·m (22.1 lb·in) design 1; 2.4 N·m (21.2 lb·in) design 2
Valve clearance (camshaft to roller)IN 0.0762 mm (0.003 in); EX 0.254 mm (0.010 in); ball stud locknut 20 N·m (177 lb·in)
Alternator drive beltStretch-to-fit, no idler; replace every 300 hours or 3 years. Alternator M10 x 60 screws: front first 7 N·m (62 lb·in), then front and rear 50 N·m (36.8 lb·ft)

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, fuel filter, gear case oil, gear case plug gaskets, propeller cotter pin

    Check: spark plugs, 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, fuel filter, gear case oil, gear case plug gaskets, propeller cotter pin, water pump impeller

    Check: spark plugs, thermostat, anodes

  3. Every 300 hours or 3 years

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

    Check: 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 150/150 SeaPro/150 Pro XS FourStroke service manual, 90-8M0231655. 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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