Yamaha F4A Owner's Manual page 84

Trouble
C. Engine power loss.
Possible Cause
1. Propeller damaged.
2. Propeller pitch or diameter incorrect.
3. Trim angle incorrect.
4. Motor mounted at incorrect height
on transom.
5. Warning system activated.
6. Boat bottom fouled with marine
growth.
7. Spark plug(s) fouled or incorrect
type.
8. Weeds or other foreign matter
tangled on gear housing.
9. Fuel system obstructed.
10. Fuel filter clogged.
11. Fuel contaminated or stale.
12. Spark plug gap incorrect.
1. Have propeller repaired or
replaced.
2. Install correct propeller to operate
outboard at its recommended
speed (r/min) range.
3. Adjust trim angle to achieve most
efficient operation.
4. Have motor adjusted to proper
transom height.
5. Find and correct cause of warning.
6. Clean boat bottom.
7. Inspect spark plug(s). Clean or
replace with recommended type.
8. Remove foreign matter and clean
lower unit.
9. Check for pinched or kinked fuel
line or other obstructions in fuel
system.
10. Clean or replace filter.
11. Fill tank with clean, fresh fuel.
12. Inspect and adjust as specified.
5-3
E
Remedy