Mercury / Mariner V6 3.0 L 225 / 225 EFI / 250 EFI two-stroke, and 3.0 Litre Marathon / SeaPro service guide

Quick answers

What two-stroke oil does a Mercury / Mariner V6 3.0 L 225 / 225 EFI / 250 EFI two-stroke, and 3.0 Litre Marathon / SeaPro use?

Quicksilver TC-W3 2 Cycle Outboard Oil.

What is the fuel to oil ratio for a Mercury / Mariner V6 3.0 L 225 / 225 EFI / 250 EFI two-stroke, and 3.0 Litre Marathon / SeaPro?

Oil injected: gasoline with oil injection, gasoline/oil ratio 50:1.

What gear oil does a Mercury / Mariner V6 3.0 L 225 / 225 EFI / 250 EFI two-stroke, and 3.0 Litre Marathon / SeaPro use, and how much?

Quicksilver Gear Lubricant in the maintenance section; the lower unit section fills with Quicksilver Super Duty Lower Unit Lubricant. Quantity: 28 fl oz (828 ml) for every ratio (1.64:1, 1.75:1 and 1.87:1); fill through the fill hole until lubricant flows out of the vent hole with no air bubbles.

What spark plug does a Mercury / Mariner V6 3.0 L 225 / 225 EFI / 250 EFI two-stroke, and 3.0 Litre Marathon / SeaPro use?

3 Litre Work and 225 carbureted, 1994 to 1996, serial 0D280813 to 0G437999: NGK BPZ8H-N-10. 3 Litre Work and 225 carbureted, 1997, serial 0G438000 and up: Champion QL77CC. 225 EFI and 250 EFI, 1994 to 1997: Champion QL77CC. Qty 6. Gap: NGK BPZ8H-N-10: 0.040 in. (1.0 mm). Champion QL77CC: 0.035 in. (0.89 mm).

How often should a Mercury / Mariner V6 3.0 L 225 / 225 EFI / 250 EFI two-stroke, and 3.0 Litre Marathon / SeaPro be serviced?

The factory schedule lists: Every 100 hours of use or once yearly, whichever occurs first. 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 V6 3.0 L 225 / 225 EFI / 250 EFI two-stroke, and 3.0 Litre Marathon / SeaPro?

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 / Mariner V6 3.0 L 225 / 225 EFI / 250 EFI two-stroke, and 3.0 Litre Marathon / SeaPro?

650 ± 50 RPM (225 carbureted, 225 EFI and 250 EFI). Idle mixture screw 1-1/2 ± 1/4 turns out on the carbureted 225.

What is the propeller nut torque on a Mercury / Mariner V6 3.0 L 225 / 225 EFI / 250 EFI two-stroke, and 3.0 Litre Marathon / SeaPro?

55 lb ft (74.5 N·m), nut recessed into the tab washer; bend 3 tabs down.

Maintenance specs

Two-stroke engine oil	Quicksilver TC-W3 2 Cycle Outboard Oil
Fuel to oil ratio	Oil injected: gasoline with oil injection, gasoline/oil ratio 50:1.
Gear oil	Quicksilver Gear Lubricant in the maintenance section; the lower unit section fills with Quicksilver Super Duty Lower Unit Lubricant
Gear oil quantity	28 fl oz (828 ml) for every ratio (1.64:1, 1.75:1 and 1.87:1); fill through the fill hole until lubricant flows out of the vent hole with no air bubbles
Gear oil fill screw and vent screw	Fill screw (magnetic) and vent screw, each with a sealing washer: 60 lb in (6.8 N·m). Non-ratcheting gear housing, serial 0G438000 and up: magnetic screw and screw assembly, 60 lb in each; ratcheting gear housing, serial 0G437999 and below: magnetic screw, qty 2, 60 lb in each. Vent screw in first, then the fill screw
Spark plug	3 Litre Work and 225 carbureted, 1994 to 1996, serial 0D280813 to 0G437999: NGK BPZ8H-N-10. 3 Litre Work and 225 carbureted, 1997, serial 0G438000 and up: Champion QL77CC. 225 EFI and 250 EFI, 1994 to 1997: Champion QL77CC. Qty 6
Spark plug gap	NGK BPZ8H-N-10: 0.040 in. (1.0 mm). Champion QL77CC: 0.035 in. (0.89 mm)
Spark plug torque	20 lb ft (27.0 N·m)
Idle speed	650 ± 50 RPM (225 carbureted, 225 EFI and 250 EFI). Idle mixture screw 1-1/2 ± 1/4 turns out on the carbureted 225
Thermostat	143 °F in the EFI component views; on test it must begin to open at 140 to 145 °F (60 to 63 °C). Water pressure 1-1/2 to 4-1/2 psi at idle, 8 to 10 psi minimum at 5000 RPM
Fuel filter	Carbureted models: check the engine fuel filter for contaminants. EFI models: replace the water separating fuel filter
Anodes	Two on the gear case and one on the bottom of the transom bracket: replace before completely eroded; never paint or coat them
Propeller nut	55 lb ft (74.5 N·m), nut recessed into the tab washer; bend 3 tabs down
Power trim fluid	Quicksilver Power Trim and Steering Fluid; if not available, automotive automatic transmission fluid (ATF Type F, FA, Dexron II or Dexron III)

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 of use or once yearly, whichever occurs first

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

   Check: spark plugs, anodes

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

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

   Check: spark plugs, anodes

Source: Mercury/Mariner 225, 225 EFI, 250 EFI, 3.0 Litre Marathon, 3.0 Litre SeaPro service manual, 90-822900R3, December 1997. Specs can change by model year and serial number, so always confirm your exact model from the serial tag on the clamp bracket.