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Mercury / Mariner 50 / 55 / 60 and 45 Jet two-stroke, 3 cylinder (849 cc) service guide

Oil, gear oil, spark plugs and the service schedule for the Mercury / Mariner 50 / 55 / 60 and 45 Jet two-stroke, 3 cylinder (849 cc) (45 to 60 hp, two-stroke), from the factory service manual, plus how we service it in Hawaiʻi.

Models covered: 45 Jet, 50, 55 Marathon, 55 SeaPro, 60, 60 Big Foot, 60 Marathon and 60 SeaPro two-strokes: 3 cylinders, loop charged, 51.8 cu in (849 cc): serial 0D000750 and above (United States), 09671687 and above (Belgium). Two gear housings: 1.64:1 on the 50/55/60 and 2.3:1 on the 60 SeaPro / Marathon and 60 Big Foot. The 45 Jet has a jet drive (section 6C).

Quick answers

What two-stroke oil does a Mercury / Mariner 50 / 55 / 60 and 45 Jet two-stroke, 3 cylinder use?
Quicksilver TC-W II or TC-W 3 2-Cycle Outboard Oil (NMMA certified).
What is the fuel to oil ratio for a Mercury / Mariner 50 / 55 / 60 and 45 Jet two-stroke, 3 cylinder?
Pre-mixed gasoline and oil 50:1 (25:1 break-in). Oil injected engines: during break-in run 50:1 in the fuel tank on top of the 50:1 from the oil pump (25:1 in total) for the first 15 gallons of fuel.
What gear oil does a Mercury / Mariner 50 / 55 / 60 and 45 Jet two-stroke, 3 cylinder use, and how much?
Quicksilver Gear Lube (or Quicksilver Super-Duty Lower Unit Lubricant); do not use automotive grease. Quantity: 50/55/60 (1.64:1): 11.5 fl oz (340 ml). 60 SeaPro / Marathon and 60 Big Foot (2.3:1): 22.5 fl oz. Fill until lubricant flows from the first vent hole, plug it, then fill until it flows from the second vent hole.
What spark plug does a Mercury / Mariner 50 / 55 / 60 and 45 Jet two-stroke, 3 cylinder use?
NGK BP8H-N-10, qty 3. Gap: 0.040 in (1.0 mm).
How often should a Mercury / Mariner 50 / 55 / 60 and 45 Jet two-stroke, 3 cylinder be serviced?
The factory schedule lists: First 20 hours, salt water; First 25 hours; Every 100 hours or once a year before storing. 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 / Mariner 50 / 55 / 60 and 45 Jet two-stroke, 3 cylinder?
The factory schedule gives no replacement interval. 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 / Mariner 50 / 55 / 60 and 45 Jet two-stroke, 3 cylinder?
675 ± 25 RPM; idle mixture screw preset 1-1/8 ± 1/4 turns out on the 50, 1-1/2 ± 1/4 on all other models.
What is the propeller nut torque on a Mercury / Mariner 50 / 55 / 60 and 45 Jet two-stroke, 3 cylinder?
Minimum 55 lb ft (74.5 N·m), then bend the tab washer; re-tighten after first use.

Maintenance specs

Two-stroke engine oilQuicksilver TC-W II or TC-W 3 2-Cycle Outboard Oil (NMMA certified)
Fuel to oil ratioPre-mixed gasoline and oil 50:1 (25:1 break-in). Oil injected engines: during break-in run 50:1 in the fuel tank on top of the 50:1 from the oil pump (25:1 in total) for the first 15 gallons of fuel
Gear oilQuicksilver Gear Lube (or Quicksilver Super-Duty Lower Unit Lubricant); do not use automotive grease
Gear oil quantity50/55/60 (1.64:1): 11.5 fl oz (340 ml). 60 SeaPro / Marathon and 60 Big Foot (2.3:1): 22.5 fl oz. Fill until lubricant flows from the first vent hole, plug it, then fill until it flows from the second vent hole
Gear oil fill plug and two vent plugsStandard housing: fill plug (magnetic) and two vent plugs, 35 to 80 lb in (3.8 to 8.8 N·m). New gaskets on all three; install both vent plugs before the fill plug
Lower unit holding pressure10 to 12 psi at the vent hole, must hold 5 minutes; turn the drive shaft and prop shaft and move the shift rod while pressurized (both gear housings)
Spark plugNGK BP8H-N-10, qty 3
Spark plug gap0.040 in (1.0 mm)
Idle speed675 ± 25 RPM; idle mixture screw preset 1-1/8 ± 1/4 turns out on the 50, 1-1/2 ± 1/4 on all other models
Thermostat120° thermostat (parts list); a poppet valve opens before 2500 RPM. Water pressure 1 to 3 psi (7 to 21 kPa) at idle in neutral, not over 12 psi (83 kPa) at 2500 RPM
AnodesThe trim tab is the anode, plus a sacrificial anode: check for damage or deterioration from salt water. Replace the trim tab if 50% or more is consumed, never paint it. Trim tab bolt 22 lb ft (29.8 N·m)
Propeller nutMinimum 55 lb ft (74.5 N·m), then bend the tab washer; re-tighten after first use

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. First 20 hours, salt water

    Replace: gear case plug gaskets

  2. First 25 hours

    Replace: gear case oil, gear case plug gaskets

  3. Every 100 hours or once a year before storing

    Replace: gear case oil, gear case plug gaskets

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

    Replace: gear case oil, gear case plug gaskets, water pump impeller

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/Mariner 45 Jet, 50, 55, 60 service manual, 90-817643R1, December 1996. 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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