1983 Yamaha 30EN Outboards Service Manual, Page 28Get this manual
BATTERY(For erectric motor) 1The fluid level should be between the upper and lower level marksUse only distilled water if refilling is necessary 1Upper level
2 Lower level
Normal tap water contains minerals which are harmful to battery; therefore, refill only with distilled water
TEST PROPELLER Whenever the motor is tested (for instance, before it is delivered to the customer or after being overhauled) be sure to use test tank and test propellerIf the originally mounted propeller is used, the test tank may overflow or the water level may fluctuate sharply, thus causing cavitation with marked increase in rpm or propeller slipTherefore, it is impossible to check if the motor has been correctly overhau ledThe test propeller is designed to turns stably even in the test tan kI the tachometer readi ngs are within the specified speed range when the motor is run with the test propeller, the motor is considered to be properly servicedIf the engine speed is far below the specified speed, the motor will have to be checked againSpecified motor speed: 5,000 5,200 rmin