Mercury Mariner Outboards 2.2 / 2.5 / 3.0 Service Shop Manual, Page 21Get this manual
Ignition Breaker Points Cleaning and Inspection Cleaning
1Dirty contact points should be dressed with few strokes of cleanfine-cut contact file File should not be used on other metals and should not be allowed to become greasy or dirtyNormal point condition is overall grey colorNOTE: Never use emery cloth to clean contact points2After considerable use, contact surfaces may not appear bright and smooth, but this is not necessarily an indication that points are not functioning satisfactorilyDo not attempt to remove all roughness nor dress point surfaces down smooth Merely remove scale or dirt3Badly burned or pitted contact points should be replaced and cause of trouble eliminated
3If contact point opening is too smallpoints will be closed for too much operating timeAverage current flow thru points will be too highso points will burn rapidly and arcing will occur between points and result in low secondary voltage and engine miss4High series resistance in condenser circuit will prevent normal condenser action, so contact points will burn rapidly This resistance may be caused by loose condenser mounting or lead connectionor by poor connections inside condenser