1984-1986 Mercury Force 9.9 and 15HP Outboards Service Manual, Page 29Get this manual
Pr.Umlnary reat 1Checkspark: ARemove spark plug8CAttach lead wire and ground plug against cylinder Crank engine to determine If there is sufficient spark to jump gapon plug weak or defective condenserTest or replace CPoints built up on negative (stationary) side, eroded on positive (movable) side indicates incorrect condenserReplace with proper part 4Check for poorly grounded or defective coilTest or replace coil Te.t EquipmentTo accurately determine the condition of components of the ignition systeman ignition tester should be usedWithout the use of test equ ipmentcomponents may be replaced needlesslyA wide variety of ignition testers are available from various manufacturersIn additionsome automotive testers having the proper specifications can be used The use of ignition testers is particularly recommendedsince these un its have provisions for checking all functions of the ignition system The following tests are made with the Merc-O-Tronic analyzer
A bright blue spark should be evidentA weak, yellowish or red spark indicates insufficient spark voltage 2If there is insufficient spark voltage check the following possible causeAPoor groundsCheck groundsBDamaged or worn high tension leadReplaceCMalfunctioning stop switch Disconnect leads from stop switch and repeat testIf defective, reptace SPA;; PLUG CONDENSER