Tohatsu MFS9.9E / MFS15E / MFS20E Fi (fuel injected, 2017) service guide

Quick answers

How much oil does a Tohatsu MFS9.9E / MFS15E / MFS20E Fi take?

1.2 L (1.26 US qt) with filter; 1.0 L (1.05 US qt) without filter; fill to the upper dipstick mark.

What engine oil does a Tohatsu MFS9.9E / MFS15E / MFS20E Fi use?

4-stroke engine oil, API SH, SJ or SL; SAE 10W-30 or 10W-40.

What gear oil does a Tohatsu MFS9.9E / MFS15E / MFS20E Fi use, and how much?

Hypoid gear oil, API GL-5, SAE #80-90. Quantity: 465 cm³ (15.7 fl oz); fill from the lower plug hole with the motor vertical.

What spark plug does a Tohatsu MFS9.9E / MFS15E / MFS20E Fi use?

NGK DCPR6E. Gap: 0.8 to 0.9 mm (0.032 to 0.035 in); limit 1.2 mm (0.047 in).

How often should a Tohatsu MFS9.9E / MFS15E / MFS20E Fi be serviced?

The factory schedule lists: First 20 hours or 1 month; Every 50 hours or 3 months; Every 100 hours or 6 months; Every 200 hours or 1 year; Every 400 hours or 2 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 Tohatsu MFS9.9E / MFS15E / MFS20E Fi?

The factory schedule says to replace it at 200 hours and 400 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 MFS9.9E / MFS15E / MFS20E Fi?

950 r/min in neutral after 5 minutes warm-up; trolling 950 r/min (tachometer or diagnostic program).

What is the propeller nut torque on a Tohatsu MFS9.9E / MFS15E / MFS20E Fi?

12 N·m (9 lb·ft) [1.2 kgf·m], then a new split pin.

Maintenance specs

Engine oil	4-stroke engine oil, API SH, SJ or SL; SAE 10W-30 or 10W-40
Engine oil quantity	1.2 L (1.26 US qt) with filter; 1.0 L (1.05 US qt) without filter; fill to the upper dipstick mark
Oil filter	18 N·m (13 lb·ft) [1.8 kgf·m] with oil filter wrench P/N 3AC-99090-0; oil the O-ring; change 5 minutes or more after stopping
Gear oil	Hypoid gear oil, API GL-5, SAE #80-90
Gear oil quantity	465 cm³ (15.7 fl oz); fill from the lower plug hole with the motor vertical
Gear oil plugs	4 N·m (3 lb·ft) [0.4 kgf·m], M8 x 1.25; new gaskets; attach the upper plug first
Gear case leak test	0.05 MPa (7 psi) [0.5 kgf/cm²] through the upper plug hole, must hold 10 seconds
Spark plug	NGK DCPR6E
Spark plug gap	0.8 to 0.9 mm (0.032 to 0.035 in); limit 1.2 mm (0.047 in)
Spark plug torque	18 N·m (13 lb·ft) [1.8 kgf·m]
Idle speed	950 r/min in neutral after 5 minutes warm-up; trolling 950 r/min (tachometer or diagnostic program)
Thermostat	Starts opening 52 ± 2 °C; lift 3.0 mm (0.118 in) or more at 65 °C (149 °F); cover bolt 9 N·m (7 lb·ft) [0.9 kgf·m], new gasket
Cooling water pressure (reference)	950 r/min 10 kPa (1.54 psi); 1500 r/min 15 kPa (2.18 psi); 3000 r/min 32 kPa (4.64 psi); 5000 r/min 40 kPa (5.80 psi); 5750 r/min 45 kPa (6.53 psi), at the check port
Anodes	Replace when reduced to 2/3 of new size; do not paint or oil; retighten the anode bolt at every inspection
Propeller nut	12 N·m (9 lb·ft) [1.2 kgf·m], then a new split pin
Valve clearance, cold	IN 0.13 to 0.17 mm (0.0051 to 0.0067 in); EX 0.18 to 0.22 mm (0.0071 to 0.0087 in); lock nut 7 N·m (5 lb·ft) [0.7 kgf·m]
Timing belt	Check and replace if necessary every 100 hours or 6 months (no deflection spec). Align "1" on the driven pulley with the head mark for No. 1 TDC.

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 or 1 month

   Replace: engine oil, oil drain plug gasket, gear case oil, gear case plug gaskets, propeller cotter pin

2. Every 50 hours or 3 months

   Replace: gear case plug gaskets, propeller cotter pin

   Check: gear case oil, water pump impeller, anodes

3. Every 100 hours or 6 months

   Replace: engine oil, oil drain plug gasket, gear case oil, gear case plug gaskets, propeller cotter pin

   Check: spark plugs, fuel filter, water pump impeller, anodes

4. Every 200 hours or 1 year

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

   Check: spark plugs, fuel filter, thermostat, anodes

5. Every 400 hours or 2 years

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

   Check: spark plugs, fuel filter, thermostat, anodes

Source: Tohatsu service manual 4st 9.9/15/20 2017, MFS9.9/15/20E Fi. Specs can change by model year and serial number, so always confirm your exact model from the serial tag on the clamp bracket.