Yamato 302 User Manual

302

YAMATO MOTOR CO. LTD.

Ota • Japan

November 2012

M O D E L

M A N U A L

YAMATO EUROPE

www.YamatoRacing.co.uk

I N D E X

FORWARD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

I GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

II OPERATION OFMOTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1. Precautions prior to starting motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. How to start motor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3. If hull fails to plane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4. Things to observe and adjust during operation. . . . . . . . . . . . . . . . . . . . . . 4

5. How to stop motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

6. Care of motor after use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

7. Submerged motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

III DISASSEMBLY, INSPECTION AND REASSEMBLY . . . . . . . . . . . . . . . . . . . 7

1. Power Unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

A. Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

B. Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

C. Reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2. Magneto . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

A. Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

B. Reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

C. Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3. Carburettor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

A. Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

B. Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

C. Reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4. Gearcase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

A. Disassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

B. Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

C. Reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

IV TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

V CROSS SECTION OFMOTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

VI PERFORMANCE CURVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

VII SPECIFICATION FORMODEL 302 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

FO RWA RD

The Yamato model 302 is a 396cc / 24. 2 cubic inch stock racing engine. Like it's

predecessors - the models 80, 102 and 202 - this motor was developed specifically

for use in the multi-billion Yen parimutuel boat racing industry in Japan. These

motors are required to run heats, day after day with perfect reliability at racing

speeds. Therefore, like engines in commercial aircraft, they have been “over-

designed” in relation to the job they perform.

Essentially, this 33 h.p. engine is a strong twin which has been detuned by use of a

low compression head, mild-port timing and one small carburettor. When putting out

33 h.p. at 6,600 rpm the 302 is just Ioafing. No wonder the Yamato has become the

biggest and most popular class in UIM and APBA racing. Compared with other stock

powerheads which vibrate, crack and fail at racing speed these engines are made

virtually "Bullet Proof". Ask any racer that owns a model 80, 102 or 202. You too will

be convinced that the model 302 is the best buy today on the motorboat racing

scene.

– 1 –

I. GENERAL

From the manufacturer of Yamato Motors, we sincerely thank you for selecting the

Yamato model 302 racing outboard motor. To operate this outboard motor safely and

efficiently, please read this instruction manual carefully. It will help you get a good

understanding of the precautions in operation and how to service and maintain it for

maximum performance, reliability and extended life.

As in most form of racing, there is risk which may bodily injury. The Yamato Motor

Co. suggest that extreme caution be taken whenever you operate this motor and

cannot be responsible or liable for any mishaps that may occur while operating this

motor.

– 2 –

II OPERATION OF MOTOR

II - 1 Precaution Prior to Starting Motor

A. Check thumb screw handles to be sure it is tight.

B. Check for oiI in gearcase.

C. Check condition of high tension wires and spark plugs. Ensure it is firmly tightened.

D. Check fuel in tank to be sure sufficient quantity remains for the anticipated run.

E. Check for proper engine height and angle.

F. Check steering system for proper installation and tightness.

G. Check throttle system for tightness. Be sure it is free from binding and free to

return to closed position.

H. When the motor is coId, it is suggested that the motor be warmed up prior to

launching. For safety sake, we suggest that the propeller be removed.

Caution: Remove spark plug wires whenever propeller is removed or installed.

II - 2 How to Start Motor

A. Set fuel cock in vertical position, air vent (located on fuel cap) opened, main needle

opened 1-1/2 turn, and spark plug wire attached to the appropriate plug.

B. Check float pin. Approximately 8mm (

5

/16") should be protruding above carburettor

float cover.

C. Set timing handle about midway of travel.

D. Pull choke lever (for cold motor only). See figure1.

E. On pre-heated motors, do not use choke. Instead, open throttle approximately 1/8

to 1/4. However for cold motor DO NOT OPEN THROTTLE.

F. Wrap starter rope 1-1/2 to 2 turns on starter pulley.

G. Pull starter rope vigorously, repeat if necessary.

H. As soon as motor starts, push choke in. See figure 2.

I. If motor starts but stops immediately, it may or may not be necessary to reset

choke.

J. Repeat step G and H.

K. After motor starts, shift timing handle all the way to the right (exhaust side).

L. Increase motor RPM.

– 3 –

M

. For safety reasons, we suggest that the air idling screw be set all the way in and the

throttle stop backed-off completely so that the motor will not continue to run if the driv-

er is thrown out of the boat.

Figure 1 Figure 2

II - 3 If Hull Fails to Plane

A. Stop motor after 30 seconds.

B. Check transom height and angle.

C. Check for foreign object around propeller and lower unit.

D. Check for damaged around / or wrong propeller.

E. Check motor. If motor lacks power, see trouble-shooting chart.

II - 4 Things to Observe and Adjust During Operation

A. Be sure timing lever (Magneto #1) is in full advanced position.

B. Open throttle for maximum power.

C. Adjust high speed main needle (Carb #16) for for maximum power.

D. Check water outlet. Be sure it is not steaming.

E. Check RPM (if tachometer is fitted). Do not exceed 8,000 rpm.

F. Listen for any unusual noise.

II - 5 How to Stop Motor

A. Release throttle lever.

B. If kill-switch is installed, use it to stop motor.

C. Alternate method of stopping motor is to shift timing lever toward the left (intake side).

– 4 –

I

I - 6 Care of Motor After Use

A. Wipe spilled gasoline with clean rag.

B. Wipe water, around powerhead.

C. If motor has been used in salt water, flush motor internally as well as externally with

fresh water. CAUTION: Do not tip motor upside down. Water can enter the exhaust

port and can cause serious damage.

D. CAUTION: When laying motor on its side, be sure the exhaust side faces down.

II - 7 Submerged Motor

A. If motor, is submerged in water for any reason, take the following action immediately:

1. Remove propeller.

2. Remove spark plug and cylinder head (remove cylinder head only when sub-

merged at high speed). Cylinder head gasket is often bIown due to hydraulic ham-

mer. The gasket acts as a fuse which minimises further internal damage.

3. Turn motor by hand. If complete revolution is possible without any bind, complete

the following:

a. If motor has been submerged in salt water, flush motor with fresh water through

carburettor while turning motor slowly. CIean exterior parts with fresh water.

b. Remove starter pulley and coil plate assembly (see par III-2). Flush with clean

fresh water. Clean and dry all electrical parts. Reinstall starter pulley only.

c. Drain fuel tank, fuel line and carburettor.

d. Set motor with cylinder head facing down.

e. Crank motor several times.

f. Turn motor so that exhaust-side is facing down.

g. Repeat step e.

h. Repeat step d.

i. Crank motor. Repeat step d thru h untiI all water is expelled.

j. Flush with fresh mixture of petrol and oil.

k. Repeat step d thru h until most of the petrol and oil mixture is expelled. Wipe

all petrol and oil that may have spilled on motor.

I. Reassemble magneto assembly.

– 5 –

– 6 –

m

. Attach high tension wires to spark plug. GROUND spark plug.

n. Pull starter pulley and check spark plug. Both plugs must be firing.

o. Reassemble (except propeller), refuel and run motor, for 30 seconds at intermediate

speed.

p. Replace propeller. CAUTION : Remove spark plug wire when installing or removing

propeller.

q. Install on hull and run at least ten minutes at half throttle.

4. If motor binds when turned by hand, internal damage such as bent connecting rod, bent

crankshaft, crankcase and/or fracture in cylinder may have occurred. Remove as much

water as possible by following step 3-a thru 3-i. Wash and coat internal and external

parts with oil. Complete disassembly is recommended.