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Mercury OptiMax 115 / 135 / 150 / 175 (2.5L) service guide

Oil, gear oil, spark plugs and the service schedule for the Mercury OptiMax 115 / 135 / 150 / 175 (2.5L) (115 to 175 hp, two-stroke), from the factory service manual, plus how we service it in Hawaiʻi.

Models covered: Mercury 115, 135, 150, 150 Pro XS, 175 and 175 Pro XS OptiMax, 2.5L V6 direct fuel injection 2-stroke, serial 0G960500 and above. Older 135/150 OptiMax (1998 to 1999, serial 0G590000 to 0G960499) are in 90-855347R02, not this sheet.

Quick answers

What two-stroke oil does a Mercury OptiMax 115 / 135 / 150 / 175 use?
TC-W3 Premium Plus or OptiMax 2-Cycle Outboard Oil.
What gear oil does a Mercury OptiMax 115 / 135 / 150 / 175 use, and how much?
High Performance Gear Lubricant. Quantity: 665 ml (22.5 fl oz).
What spark plug does a Mercury OptiMax 115 / 135 / 150 / 175 use?
MY2000: NGK PZFR6H or IZFR5J, gap 0.8 mm (0.031 in). MY2001 and newer: NGK IZFR5G-11, gap 1.1 mm (0.043 in). MY2007 and newer Pro XS: NGK IZFR6J, gap 1.1 mm. qty 6.
How often should a Mercury OptiMax 115 / 135 / 150 / 175 be serviced?
The factory schedule lists: Every 100 hours or once a year. 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 OptiMax 115 / 135 / 150 / 175?
The factory schedule says to replace it at 100 hours, and we follow that. In any case we never let it go longer than a year in Hawaiʻi's salt water.
What is the idle speed of a Mercury OptiMax 115 / 135 / 150 / 175?
550 ± 25 r/min. Not adjustable; check with the CDS.
What is the propeller nut torque on a Mercury OptiMax 115 / 135 / 150 / 175?
75 N·m (55 lb·ft); bend three tabs.

Maintenance specs

Injection oilTC-W3 Premium Plus or OptiMax 2-Cycle Outboard Oil
Gear lubeHigh Performance Gear Lubricant
Gearcase capacity665 ml (22.5 fl oz)
Fill and vent screws7 N·m (62 lb·in)
Gearcase pressure test (no lube)69 to 82.7 kPa (10 to 12 psi) for 5 minutes
Spark plugMY2000: NGK PZFR6H or IZFR5J, gap 0.8 mm (0.031 in). MY2001 and newer: NGK IZFR5G-11, gap 1.1 mm (0.043 in). MY2007 and newer Pro XS: NGK IZFR6J, gap 1.1 mm. qty 6
Spark plug torqueFinger tight plus 1/4 turn, or 27 N·m (20 lb·ft)
Idle speed550 ± 25 r/min. Not adjustable; check with the CDS
ThermostatStamped 61 °C (142 °F); starts to open 60 to 62.7 °C (140 to 145 °F); fully open 73.8 °C (165 °F); lift at least 3.302 mm (0.130 in). Parts list shows 62 °C (143 °F)
AnodesTrim tab / anode bolt 34 N·m (25 lb·ft); gearcase side anode M6 x 40 screw and nut 7 N·m (62 lb·in)
Propeller nut75 N·m (55 lb·ft); bend three tabs
Power trim fluidPower Trim and Steering Fluid or ATF Type F, FA, Dexron II or III. Max leak-down 55 mm (2.2 in) in 24 hours

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: fuel filter, air filter, spark plugs, gear case oil, gear case plug gaskets, water pump impeller

    Check: anodes

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

    Replace: fuel filter, air filter, gear case oil, gear case plug gaskets, water pump impeller

    Check: spark plugs, anodes

Source: Mercury 115/135/150/150 Pro XS/175/175 Pro XS 2.5 Liter OptiMax service manual, 90-8M0057453. 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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