1963-1973 Mercruiser all Engines and Drives Service Manual Books 1 and 2, Page 29Get this manual

1963-1973 Mercruiser all Engines and Drives Service Manual Books 1 and 2, Page 29

PRE- IGN ITION and DETONATION PRE-I GN ITI ON Preignition abnorma fuel ignitioncau' by co mbustion cha mber hol spotsControl
or damage the park plugs, pi ton, va lves andinvere case res ul ts in pre-igniti (Figure 2) ! of lo clane ga lin is on' of
the mo st com mon causes of etonationEven with high lan ga linede tonation could ccur if ngine ma inte nanceneglec ted OTHER
CA USES of DETONATION WARNfNGDO NOT operate MerCruiser inhoan:l engines or stem drive with new "Iead-free" or "no-lead" gasolines_
Valve seat failure may occur from the we of these lead-free fuelsRegular leaded and low-lead fud are satisfacto ry in aU
MerCruiser four cycle enginesFigure 2Detonation Damage veradvaJl ccd ignition timing2 Lean fu mix ture near fu ll throttl
(could caused by carburetor lea king tntak ma nifold)3Cross-firin spark plu gs4 Execs accumu lation of dCI its on piston
and com bustion (:hamber (r in higher compr ion rat io) 5lnad equat m'ooli ng 01' cnuine Ly deterio ra tion ooli ng En rin