1983 Yamaha 30EN Outboards Service Manual, Page 125Get this manual
34 Check spark strength by giving the starter rope strong pullIf the spark can jump at least across an mm (0.31 in) gap, the ignition coil is considered to be in good condition If it cannot, the ignition coil should be replacedHook up the coil tester to the ignition coil as shown
6Plug in the Coil Tester7Turn the voltage selector switchCOl to
Test using an AC power source (100V, 117V, 220V and 240V) The Coil Tester can be set to any of the following voltages: AC 110V: 110V AC 117V: 128V AC 220V: 200 230V AC 240V: 230 250V Minimum spark gap8mm (0.31 in) Remove the fuse holder and fuse from the tester2Take out the voltage selector3Set the notch to the voltage indicated on the periphery4Remount the fuse and fuse holder1NOTE: The performance of the ignition coil will be affected by heatThe spark test shou Id therefore be performed at intervals of to 10 minutes for correct test results