It means that it is electric start (e), extra long shaft (xl), power trim (pt), oil injected (o).
all mercury outboards mix 50:1
The "OC" model 75 hp Mercury outboards were manufactured in 1990.
To determine the age of a 20 hp Mercury Thunderbolt with the serial number 7139300, you would typically need to consult the manufacturer's production records or a reference guide specific to Mercury outboards. However, Mercury outboards from that era have serial numbers that can often be decoded to find the year of manufacture. Without access to specific databases or records, it's difficult to provide an exact age, but generally, Mercury outboards from that range were produced in the late 1970s to early 1980s.
Only the 3 cylinder models from 1987 and up
Mercury outboards prior to 1966 use a 24:1 fuel to oil ratio.
The older model mercury outboards, with maker points, should have a 0.020" gap setting.
The "OC" model 75 hp Mercury outboards were manufactured in 1990.
Mercury Marine uses both the serial number, and the horsepower rating, to determine the year model of their outboards.
The serial number and horsepower rating for the engine is compared to the Mercury outboard model year chart.
Mercury outboards are best. Johnson Sea Striker series is good too.
In addition to the serial number, which is listed here, the horsepower of the engine is needed, to determine the year model of Mercury outboards.
A 9.8 hp Mercury outboard, serial number 5123082, would be a 1978 year model.