Suzuki outboard motors 1988 2003 repair manual., Page 153Get this manual
IGNITION AND ELECTRICAL SYSTEMS 5-41 Move the positive (+) meter lead to the alternator mounting bracket, if the voltage reading drops substantially then you know that there is bad electrical connection between the alternator and the mounting bracket The theory is to keep moving closer to the battery terminal one connection at time in order to find the area of high resistance (bad connection)Current Output Test
See Figure 39
Do not consider battery of less than 70- amplhour or 100-minute reserve capacityIf in doubt as to how large the boat requires, make liberal estimate and then purchase the one with the next higher amp ratingOutboards equipped with an onboard computer, should be equipped with battery of at least 100 to 105 amplhour capacityMARINE BATTERIES
See Figure 40
1Perform current output test as follows:
The current output test requires the use of voltlamp digital multimeter with battery load control and an inductive amperage pick-upFollow the manufacturer's instructions on the use of the equipmentaStart the engine and allow it to reach normal operating temperaturebTurn off all electrical accessoriescConnect the digital multimeter to the battery terminals and cable according to the instructionsdBring the engine to about 2,500 rpm and hold it thereeApply load to the charging system with the rheostat on the digital multimeterDo not let the voltage drop below 12 voltsf The alternator should deliver to within 10 of the rated outputIf the amperage is not within 10 and all other components test good, replace the alternator
Because marine batteries are required to perform under much more rigorous conditions than automotive batteries, they are constructed differently than those used in automobiles or trucksTherefore, marine battery should always be the No1 unit for the boat and other types of batteries used only in an emergencyMarine batteries have much heavier exterior case to withstand the violent pounding and shocks imposed on it as the boat moves through rough water and in extremely tight turnsThe plates are thicker and each plate is securely anchored within the battery case to ensure extended lifeThe caps are spill proof to prevent acid from spilling into the bilges when the boat heels to one side in tight turn, or is moving through rough waterBecause of these features, the marine battery will recover from low charge condition and give satisfactory service over much longer period of time than any type intended for automotive useFULL FIELD TESTER LOAD ADJUSTER ICARBON PILE) VOLTMETER NEGATIVE