TIMING CHANGE - Mere 1500-1400-1350-1150

Old stuff, but there are still a lot of these motors in the field.

(Attach Service Bulletin Sticker on Pages 3E-45 and 3E-53 of Your Service Manual)
There have been instances of piston detonation and/or scoring on current model 6-cylinder Mercury  Outboards. Part of this problem has been attributed to:
a. Lower than recommended octane gasoline and/or
b. Incorrect propeller installation (too high a pitch propeller for the particular application).
  When servicing Mere 1500-1400-1350-1150 Outboards for any reason, retard the spark to 210  BTDC. If detonation and/or piston scoring are experienced, retard timing on those specified models  in your area so that they are more tolerant to the occasional lower-than-recommended octane  gasoline that reaches the marine market. No significant loss of performance will he observed from  the 2% spark retard. Merc 1500 and 1150 models above Serial No. 4·23984 will have a spark setting  of 21 BTDC from production.