The Filler Dipstick by Buckshot Racing #77 replaces the original filler and vent screw used on Mercury, MerCruiser, and Parker Oildyne hydraulic trim and tilt pumps equipped with steel reservoirs. This dipstick serves two essential purposes—it allows accurate oil-level inspection and provides the necessary venting for the hydraulic reservoir.
Proper venting prevents internal pressure or vacuum from forming inside the reservoir, which can cause aeration, cavitation, or seal damage. For correct operation, the dipstick must be lightly seated, then turned counterclockwise 1½ turns. This position allows the reservoir to breathe while keeping the system sealed against fluid loss or contamination.
When overtightened, venting is blocked, leading to poor trim response and potential hydraulic failure. If too loose, dirt or moisture can enter the oil. The Buckshot Racing #77 dipstick restores the factory vent balance designed by Parker Oildyne and Mercury engineers.
OEM & Aftermarket Compatibility
Mercury part number 92459A4 identifies the complete trim and tilt pump assembly used on many Mercury, MerCruiser, Mariner, Quicksilver, and ARCO systems. The Buckshot Racing #77 dipstick replaces the filler/vent screw found on these Parker Oildyne-based hydraulic pumps with steel reservoirs.
It is compatible with a wide range of outboards from 150 to 300 horsepower, as well as MerCruiser Alpha and Bravo drives and other Oildyne-style trim pump configurations. Pumps using plastic or non-vented reservoirs require a different part.
Fill Maintenance
To check or refill fluid, ensure the drive or engine is fully trimmed down. Remove the dipstick and fill the reservoir with Mercury Trim and Tilt Fluid or Dexron III ATF until the oil reaches the bottom of the fill hole. Reinstall the dipstick, lightly seat it, and back it out 1½ turns.
After filling, cycle the trim system fully up and down to purge air, then recheck the level. Keep the dipstick vent clean to maintain proper breathing and prevent leaks. Routine inspection of the O-ring and threads helps sustain sealing integrity and system performance.
Illustration Reference Above
The diagram below identifies the Fill/Oil Level Screw (a) location and correct venting procedure.
Important
The Fill/Oil Level Screw (a) also serves as a vent for the pump reservoir. It must be turned 1½ turns counterclockwise from lightly seated to ensure proper venting for the oil pump reservoir. The dip stick from Buckshot Racing #77 replaces this screw directly and restores Mercury OEM venting behavior for outboard and offshore boat racing, high-performance bass boats and recreational boats the same.
For technical support, contact Mike Hill at +1-714-697-1716 or mike@buckshotracing77.com