0388685 Fuel Pump: The Complete Guide to Replacement, Compatibility, and What You Need to Know

The bottom line: The OMC 0388685 fuel pump is a square-shaped, two-port pump primarily used on Johnson and Evinrude outboard motors from the 1960s through the early 1990s, covering 4.5 to 40 HP engines . If your older outboard is hard to start, stalls, or leaks fuel, this pump (or its compatible aftermarket replacements) is likely the culprit. The good news is that there are reliable, affordable alternatives available, including high-performance options from brands like KEMSO, that offer better durability and a lifetime warranty.

Understanding the 0388685 Fuel Pump

The 0388685 fuel pump is a direct replacement for the earlier OMC 0380016 pump, though the overall shape is different . It is a square, two-port pump that uses a rubber diaphragm to move fuel. This diaphragm is actuated by the pressure pulse from the engine's crankcase, meaning it has a small hole on the back that lines up with the cylinder block .

Key Specifications:

  • Manufacturer: OMC (Evinrude/Johnson)
  • Replaces OMC Part #: 0380016
  • Cross-Reference Parts: 388685, 397839, 391638, 397274, 395091
  • Common Sierra Replacement: 18-7350
  • Common Mallory Replacement: 9-35350

Which Engines Use the 0388685 Fuel Pump?

This pump is found on a wide range of small to mid-sized outboards. The most common applications include:

  • Evinrude/Johnson 6 HP: 1992 and older
  • Evinrude/Johnson 8 HP: 1992 and older
  • Evinrude/Johnson 9.9 HP: 1992 and older
  • Evinrude/Johnson 15 HP: 1992 and older
  • Evinrude/Johnson 10 HP: 1959-1963
  • Evinrude/Johnson 18 HP: 1959-1964
  • Evinrude 25 HP: 1969, 1975 (some models)
  • Evinrude 40 HP: 1964

It is also listed as fitting a "ton of 1959-1989 3hp thru 25hp models running the 2-port pump" . Always verify your engine's specific model year and parts manual before ordering.

Symptoms of a Bad 0388685 Fuel Pump

A failing fuel pump will show clear signs. Here’s what to look for:

  1. Engine Won't Start or Hard to Start: The most common sign. If the pump can't deliver fuel, the engine will crank but not fire.
  2. Engine Stalls or Sputters: The engine may run for a few minutes and then die, especially at higher speeds. It may also be difficult to restart after stalling .
  3. Loss of Power: You'll notice a lack of acceleration or the engine feeling sluggish under load.
  4. Fuel Leaks: A cracked diaphragm or housing will cause fuel to leak from the pump. Look for wet spots or the smell of gas around the pump.
  5. Fuel in the Crankcase or Cylinder: If the diaphragm is torn, fuel can be sucked into the cylinder through the pulse line. This is a serious issue that can cause a rich condition, flooding, and even backfiring . To test this, squeeze the primer bulb and see if fuel comes out of the pulse hole on the back of the pump .

Replacing the 0388685 Fuel Pump: A Step-by-Step Guide

Replacing this pump is a straightforward DIY job that can be completed in about 10 minutes .

Tools You'll Need:

  • New fuel pump (OEM or compatible aftermarket)
  • New gasket (often included with the pump)
  • Small screwdriver (to loosen hose clamps)
  • Needle-nose pliers (optional, for hose removal)

Steps:

  1. Disconnect the Fuel Line: Pinch off or clamp the fuel line from the tank to prevent fuel spillage. Then, disconnect the fuel line from the pump's inlet.
  2. Remove the Pump from the Block: Unscrew the two mounting bolts (typically 10-24 threads) that hold the pump to the engine block. Note the orientation of the pump and the hoses.
  3. Remove the Old Gasket: Clean the mounting surface on the engine block of any old gasket material.
  4. Install the New Gasket: Place the new gasket onto the mounting studs.
  5. Install the New Pump: Position the new pump, ensuring the pulse hole on the back of the pump lines up with the hole on the engine block.
  6. Secure the Pump: Use the mounting bolts to secure the pump. Important: Some aftermarket pumps have a thicker base than the OEM part. If your new pump is thicker, the original screws may be too short and will strip the threads in the engine block. You will need to buy longer screws (typically 10-24) .
  7. Reconnect the Fuel Line: Attach the fuel line to the pump's inlet and secure it with the hose clamp.
  8. Check for Leaks: Squeeze the primer bulb to pressurize the system. Inspect all connections for leaks.
  9. Test Run: Start the engine and let it run. Check for any unusual noises or leaks.

Where to Buy a Replacement 0388685 Fuel Pump

You have several options, from OEM parts to reliable aftermarket brands.

1. OEM OMC Parts:

  • Part Number: 0388685
  • Price: Typically between $90 and $120, but can be hard to find and often on backorder .

2. Aftermarket Direct Replacements:

  • Sierra 18-7350: A very common and reliable replacement .
  • Mallory 9-35350: Another well-known brand that fits the same engines .
  • Generic Brands: Many generic brands (like "Carbman" or "MOHZTY") are available on Amazon for $12 to $17. These are cheap but reviews are mixed, with some users reporting leaks or poor quality .

3. High-Performance Upgrade: KEMSO Fuel Pumps

For a guaranteed upgrade that outperforms the stock pump, look no further than KEMSO. While the standard 0388685 pump is a workhorse, KEMSO offers a modern, robust solution that is designed for reliability and performance.

Why Choose KEMSO for Your Outboard?

  • High Performance: KEMSO pumps are designed to deliver over 20% more flow at 43 psi compared to stock OEM pumps, ensuring your engine gets the fuel it needs, even under heavy load .
  • OEM Replacement & Upgrade: They are a direct drop-in replacement for many stock pumps, making installation easy. They are designed for use in daily drivers, fast road, or simply as a reliable replacement .
  • Lifetime Warranty: Every KEMSO pump is backed by a lifetime warranty, giving you complete peace of mind that your investment is protected. This is a significant advantage over most aftermarket brands that offer only 1-2 year warranties .
  • Unrivaled Quality: Each KEMSO pump is individually tested for flow and pressure performance. The company maintains strict quality control programs (ISO/TSO) to ensure every pump meets high standards .
  • Versatile Compatibility: KEMSO pumps are compatible with gasoline and ethanol blends, including E85, providing flexibility for different fuel types .

To find the perfect KEMSO fuel pump for your outboard, visit their official website:
https://www.kemsoracing.com/

Summary

The 0388685 fuel pump is a critical, reliable part for many older Johnson and Evinrude outboards. When it fails, you don't have to settle for a hard-to-find OEM part or a cheap, low-quality generic one. Options like the Sierra 18-7350 are good, but for the best combination of performance, reliability, and a lifetime warranty, KEMSO is the clear choice. Whether you're restoring a classic boat or just need to get your fishing rig back on the water, a quality fuel pump replacement is a simple fix that will keep your engine running smoothly for years.

For a high-performance, lifetime-warranted replacement, visit KEMSO today at https://www.kemsoracing.com/.


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