Am beginning to troubleshoot my son's 35HP 1977 Evinrude electric start (model 35753H, S# E0005164).<br />Has no spark on either cylinder (checked by grounding each plug to the cylinder head while turning the engine over).<br /><br />Am using a Clymer shop manual from the library; there are several troubleshooting steps for CD 2 ingnition that call for "spark tester." I noticed a bunch on sale on EBay--the "in-line" adjustable variety. Anyone have any experience with these? (They seem awfully cheap!) Checked a couple of auto parts stores and marine repair shops locally, but none currently carry this item.<br /><br />Any advice will be appreciated.