1985 Mercury Outboard V-300 V-3.4L Shop Service Manual, Page 143Get this manual
POWERHEAD BREAK-IN ACAUTION
To avoid possible engine damage, "Break-In Procedure", followingMUST BE completed BEFORE operating engine at lull throWe continuouslyTh Ol'l'ner must he advised tha break-in proced ures must be foll owed euctl wh en an overhau led engine is returned to service(Refer toBreak-In Procedure", fo llowing
ACAUTION
Follow break-In procedure carefullyMix gasoli ne and oil during the lO-hour brea ki period at 25: rali o, as shown in Ihe fo llo wing cha rtOperate new otor (25003500 RPM11'0'0 hoursAfl er 11'0'0 hoursIhe mo tor ma Tun al an speed, although sustained ope rat ion fu ll throlt le sh ould be avoided for an additional eight (8) ho urs