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Tohatsu MD40A / MD50A TLDI (3 cylinder, 697 cc, direct injection two-stroke) service guide

Oil, gear oil, spark plugs and the service schedule for the Tohatsu MD40A / MD50A TLDI (3 cylinder, 697 cc, direct injection two-stroke) (40 to 50 hp, two-stroke), from the factory service manual, plus how we service it in Hawaiʻi.

Models covered: TLDI 40A and 50A in the EPTO, EFTO and EFO versions: 3 cylinder inline, 697 ml (42.5 cu in), bore 68 x stroke 64 mm, two-stroke low-pressure direct injection with air compressor, L-CDI ignition and ECU. 40A 29.4 kW, 50A 36.8 kW; full-throttle range 5150 to 5850 rpm; gear ratio 1.85:1 (13:24); auto-mixing oil injection with a 2 L oil tank. The later MD30B2 / MD40B2 / MD50B2 have their own sheet.

Quick answers

What two-stroke oil does a Tohatsu MD40A / MD50A TLDI use?
Genuine engine oil or TC-W 2-stroke marine outboard oil; only those products that have been approved.
What gear oil does a Tohatsu MD40A / MD50A TLDI use, and how much?
Genuine gear oil or API GL5, SAE #80. Quantity: 500 ml (16.9 US fl oz), approx.
What spark plug does a Tohatsu MD40A / MD50A TLDI use?
Champion RC10ECC, qty 3. Gap: 1.0 to 1.1 mm (0.039 to 0.043 in).
How often should a Tohatsu MD40A / MD50A TLDI be serviced?
The factory schedule lists: First 10 hours or bimonthly; First 30 hours or monthly; At 50 hours or 3 months; At 100 hours or 6 months; Yearly, done with the 200 hours service 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 Tohatsu MD40A / MD50A TLDI?
The factory schedule says to replace it at 200 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 Tohatsu MD40A / MD50A TLDI?
700 rpm idling, 700 rpm trolling.
What is the propeller nut torque on a Tohatsu MD40A / MD50A TLDI?
29 to 39 N·m (3.0 to 4.0 kg-m, 22 to 29 lb-ft); replace the split pin with a new pin.

Maintenance specs

Injection (two-stroke) oilGenuine engine oil or TC-W 2-stroke marine outboard oil; only those products that have been approved
Oil tank2 L (2.1 US qt). Bleed the oil pump at its drain screw until no air is left in the clear vinyl pipes; fill the tank first. Check the oil filter for water and foreign matter
Gear oilGenuine gear oil or API GL5, SAE #80
Gear oil quantity500 ml (16.9 US fl oz), approx.
Gear oil drain and level plugs (lower and upper oil plug)Remove the lower oil plug, then the upper oil plug; fill through the lower hole until oil overflows from the upper hole; tighten the upper plug first, then the lower
Spark plugChampion RC10ECC, qty 3
Spark plug gap1.0 to 1.1 mm (0.039 to 0.043 in)
Spark plug torque25 to 30 N·m (2.5 to 3.0 kg-m, 18 to 22 lb-ft)
Idle / trolling speed700 rpm idling, 700 rpm trolling
ThermostatValve starts at 52 °C (125.6 °F), full open at 65 °C (149.0 °F), full-open lift 3 mm (0.12 in) or more
Fuel filtersEngine fuel filter (detachable cup; the red ring floats when water is present: empty the cup) and high pressure fuel filter
Propeller nut29 to 39 N·m (3.0 to 4.0 kg-m, 22 to 29 lb-ft); replace the split pin with a new pin
Air compressor drive beltCheck for wear and damage, missing teeth and oil; replace when even the slightest defect is found; mark top and bottom if it is reused. Driven pulley nut 31 to 34 N·m, drive pulley nut 140 to 160 N·m

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 10 hours or bimonthly

    Replace: gear case oil, gear case plug gaskets, propeller cotter pin

  2. First 30 hours or monthly

    Replace: gear case plug gaskets, propeller cotter pin

    Check: spark plugs

  3. At 50 hours or 3 months

    Replace: gear case plug gaskets, propeller cotter pin

    Check: fuel filter, gear case oil, water pump impeller, anodes

  4. At 100 hours or 6 months

    Replace: gear case plug gaskets, propeller cotter pin

    Check: spark plugs, fuel filter, gear case oil, water pump impeller, anodes

  5. Yearly, done with the 200 hours service or once a year

    Replace: fuel filter, gear case plug gaskets, propeller cotter pin, water pump impeller

    Check: spark plugs, gear case oil, anodes

Source: Tohatsu TLDI 40A/50A service manual, 003-21050-1. 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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