Mercury Mariner 4 and 5HP 4-Stroke Outboards Service Shop Manual 1999, Page 96Get this manual

EMISSIONS
Stratified Vs Homogenized Charge
OFI engines use stratified charge inside the comb ustion chamber to aid in reducing emis sionsAll other models use homogenized chargeThe difference between the two is:

• ATV
• Jet Ski
• Outboard Motors
• Personal Watercraft
• Snowmobiles
• Stern Drives