Mercury Mariner 30/40 4-Stroke Outboard Service Manual 1998, Page 39Get this manual
GENERAL INFORMATION
AvOd po:s'iilble or or out beyond neutral steering condition, pull on the steering wheel or tiller handle in ei ther direction may resultFailure to keep continuous firm grip on the steering wheel or tiller handle when this condition exists can result In loss of boat control as the outboard can turn freelyThe boat can nowspin out" or go into very tight maximum turn whichif unexpected, can result in occupants being thrown within the boat or out of the boatConsider the following lists carefully :
TRIMMING IN OR DOWN CAN:
1Lower the bow2Result in quicker planing off, especially with heavy load or stern heavy boat3Generally improve the ride in choppy water4Increase steering torque or pull to the right (with the normal right hand rotation
propeller)5In excess, lower the bow of some boats to point where they begin to plow with their bow in the water while on plane Th is can result in an unexpected turn in either direction called bow steering" or "over steering" if any turn is attempted or if significant wave is encountered