1986+ Mercury 6/8/9.9/10/15HP 2-stroke Factory Service Manual, Page 28Get this manual
MAINTENANCE
Positioning Outboard for Storage
Store outboard in an upright position to allow water to drain out of outboard
CAUTION
If outboard is stored tilted up in freezing temperature, trapped cooling water or rain water that may have entered the propeller exhaust outlet in the gearcase could freeze and cause damage to the outboard