Sierra Oil Pressure Sender 18-5899 Medium 80 PSI range with 1/8-27 NPT thread

The Sierra International 18-5899 is a medium-range oil pressure sender that converts engine oil pressure into an electrical signal for use with 80 PSI electric gauges.

This compact sender provides a reliable bridge between your engine and instrument panel. Built for universal replacement, it fits a wide range of marine and industrial applications where a 1/8"-27 NPT port and a 10-32 stud electrical terminal are specified. Designed to mimic factory fit and electrical response, the 18-5899 helps restore accurate oil pressure indication after a failure or during an upgrade.

What are the key specifications and why do they matter?

The unit features a 1/8" (3.2 mm) - 27 NPT thread, an 80 PSI pressure range, and a 10-32 stud terminal for the electrical connection. Those specs determine compatibility with engine ports, the maximum pressure the sender will report, and the type of gauge or wiring hardware you need. Choosing a sender with matching thread size and terminal type avoids leaks and electrical fit issues.

• Thread size: 1/8"-27 NPT — matches common oil sender ports
• Pressure range: 80 PSI — suited for higher-pressure engines and 80 PSI gauges
• Terminal: 10-32 stud — standard for many electric oil gauges
• Fit type: Universal — replacement for multiple OEM references

How does the 18-5899 install and connect to my gauge?

Installation is straightforward: screw the sender into the engine's oil pressure port using the 1/8" NPT thread and connect the gauge lead to the 10-32 stud. Use a proper torque and thread sealant rated for oil systems to prevent leaks. Grounding may require a separate chassis or engine ground depending on your gauge design.

• Mount: screw into a 1/8"-27 NPT oil port
• Electrical: attach gauge wire to 10-32 stud terminal
• Seal: use oil-safe thread sealant or Teflon tape sparingly
• Grounding: confirm gauge grounding method for accurate readings

Which engines and OEM parts does this replace?

The 18-5899 is a drop-in-style replacement for many marine and powerplant senders from multiple manufacturers. It is commonly used to substitute failed or corroded senders from stern drives, inboard engines, and other applications where the 1/8" NPT/80 PSI/10-32 configuration matches. Cross-references include well-known part numbers and legacy replacements across brands.

• Compatible with a range of OEM and aftermarket references for marine drives
• Common replacement for Stern Drive and inboard oil sender applications
• Useful when original sender shows faulty or intermittent readings

What should I check before buying to ensure fit and function?

Verify the thread size on your engine port and the pressure range required by your gauge before ordering. Confirm that your oil gauge expects an 80 PSI sender and that the electrical terminal type (10-32 stud) matches existing wiring or terminals. If in doubt, compare the old sender’s physical thread and electrical connection to the Sierra unit.

• Measure or confirm the engine's sender port thread (1/8"-27 NPT)
• Confirm gauge range is compatible with an 80 PSI sender
• Check the gauge wiring terminal to match a 10-32 stud
• Inspect for space and access to the port for proper installation

Who is this for: The Sierra 18-5899 oil pressure sender is aimed at boat owners, mechanics, restorers, and fleet technicians seeking a dependable, universal replacement for medium-range oil pressure monitoring. It suits anyone replacing a failing sender with matching thread and terminal specifications or upgrading gauges on marine and industrial engines where accurate 0–80 PSI indication is required.