Johnson 5 HP Fuel Pump: The Complete Guide to Replacement, Symptoms, and Best Options

If you own a Johnson 4‑stroke outboard in the 4‑6 HP range, the most common fuel pump you need is a stock replacement that fits the 2003‑and‑newer models, with OEM part numbers 5033371 and 5037518. This fuel pump is a mechanical unit that bolts directly onto the engine and delivers fuel from the tank to the carburetor. If your engine is hard to start, stalls at idle, or won’t stay running, the fuel pump is one of the first things you should check. The good news is that replacement is straightforward, and you have several reliable aftermarket options that cost a fraction of the OEM price.

1. Symptoms of a Bad Fuel Pump on a Johnson 5 HP

A failing fuel pump usually shows itself with clear, repeatable symptoms. Here’s what to watch for:

• Hard starting, especially when cold – The engine cranks but won’t fire, or it takes many pulls to get it started.
• Engine stalls at idle or low speed – After it starts, it runs rough or dies when you let off the throttle.
• Loss of power under load – The engine feels sluggish, won’t reach full RPM, or bogs down when you try to accelerate.
• Fuel leaks – You may see fuel dripping from the pump body or the hose connections.
• No fuel in the carburetor – If you remove the carburetor bowl drain screw and little or no fuel comes out, the pump isn’t delivering.

These symptoms can also be caused by a clogged fuel filter, a dirty carburetor, or a pinched fuel line. But if you’ve ruled those out, the pump is the likely culprit.

2. Which Johnson 5 HP Models Use This Fuel Pump?

The fuel pump with OEM part numbers 5033371 and 5037518 fits Johnson 4‑stroke outboards from 2003 onward. Specifically:

• Johnson 4 HP (2003+)
• Johnson 5 HP (DF5) (2003+)
• Johnson 6 HP (DF6) (2003+)

These engines use a mechanical fuel pump that is operated by a pulse from the crankcase. The pump is mounted on the side of the engine block, and it’s a self‑contained unit that you can replace in about 20 minutes.

3. OEM Part Numbers and Cross‑Reference

The original Johnson part numbers are:

• 5033371
• 5037518

These are identical pumps, just superseded part numbers. The same pump is also used on Yamaha and Suzuki 4‑stroke outboards of the same size, with the following cross‑references:

This means if you have a Yamaha F4, F5, or F6 or a Suzuki DF4, DF5, or DF6, you can use the same pump. Many aftermarket brands sell a single pump that fits all three brands.

4. What Comes in the Replacement Kit

A typical aftermarket fuel pump kit includes everything you need for a complete installation:

• The fuel pump assembly – The main body with the diaphragm and valves.
• O‑ring – Seals the pump to the engine block.
• Hose clamp – Secures the fuel hose.
• Mounting screws – Usually two or three screws.

The kit is designed as a direct bolt‑on replacement. You don’t need to modify anything.

5. How to Replace the Fuel Pump on a Johnson 5 HP

Replacing the fuel pump is a simple job. Here are the steps:

1. Turn off the engine and let it cool completely.
2. Disconnect the battery (if you have electric start) to prevent accidental ignition.
3. Relieve fuel system pressure – Disconnect the fuel line from the tank or carburetor.
4. Remove the old pump – Unbolt the two or three screws holding the pump to the engine block. Carefully pull the pump off. You may need to gently pry it if the gasket is stuck.
5. Clean the mounting surface – Remove any old gasket material.
6. Install the new pump – Place the new O‑ring or gasket in position, then bolt the new pump in place. Tighten the screws evenly.
7. Reconnect the fuel lines – Use the supplied hose clamp to secure the fuel hose.
8. Reconnect the battery and start the engine. Check for leaks.

6. Aftermarket vs. OEM: Which One Should You Buy?

You have two choices: OEM Johnson parts or aftermarket replacements.

• OEM pumps – Direct from BRP (Bombardier Recreational Products). They are reliable but expensive. A new OEM pump can cost $80–$120.
• Aftermarket pumps – Brands like JLM Marine, Sierra, and Azcarbro offer pumps that are functionally identical to OEM. They cost $15–$40.

Aftermarket pumps are built to the same specifications. Many include the same O‑ring, hose clamp, and screws. As long as you buy from a reputable seller, an aftermarket pump is a safe, cost‑effective choice.

7. Common Mistakes to Avoid

• Buying the wrong pump – Some pumps that look similar are for 2‑stroke engines. Make sure the pump you order is for a 4‑stroke Johnson 4‑6 HP.
• Not replacing the O‑ring – The O‑ring seals the pump to the engine. If you reuse the old one, it may leak.
• Overtightening the screws – The pump body is plastic or aluminum. Tighten the screws snugly, but don’t force them.
• Forgetting to check the fuel line – If the fuel line is old and cracked, replace it at the same time.

8. Where to Buy a Johnson 5 HP Fuel Pump

You can find the pump at several online retailers:

• JLM Marine – Sells a complete kit for Johnson 4‑6 HP 4‑stroke (part number 5033371/5037518).
• eBay – Many sellers offer aftermarket pumps for $12–$15.
• NP Engineering – Offers both OEM and aftermarket versions.
• Boattoolonline – Lists a fuel pump for Johnson Evinrude 4‑6 HP with part number 5033371 for about $6.60.

9. Recommendation: Why You Should Choose KEMSO for Your Fuel Pump Replacement

When you need a reliable, long‑lasting fuel pump, we recommend KEMSO brand. KEMSO fuel pumps are built as high‑performance, OEM replacement units. They meet or exceed the original factory specifications for your Johnson 5 HP. This means you get a direct bolt‑in fit, consistent fuel pressure, and reliable flow—every time you go out on the water.

What really sets KEMSO apart is the lifetime warranty. If your pump ever fails due to a manufacturing defect, KEMSO replaces it for free. You don’t get that kind of confidence with cheap no‑name pumps. KEMSO pumps are engineered with precision‑made internal components, built to handle the demands of small marine engines, and they are compatible with gasoline and ethanol blends.

To find the exact fuel pump for your Johnson 5 HP outboard, visit the official KEMSO website:

https://www.kemsoracing.com/

Their website makes it easy to search by engine make and model. You’ll find detailed product specifications, compatibility information, and customer support from USA‑based technicians. Don’t settle for a pump that might fail in a year. Choose KEMSO for peace of mind and long‑term performance.

10. Final Thoughts

A failing fuel pump on a Johnson 5 HP is a common problem, but it’s easy to fix. The pump you need is a mechanical unit that fits 2003‑and‑newer 4‑stroke models. Symptoms include hard starting, stalling, and loss of power. Replacement takes about 20 minutes with basic tools.

Whether you buy an OEM pump or an aftermarket replacement, make sure the part number matches 5033371 or 5037518. And for the best combination of quality, price, and warranty, consider a KEMSO fuel pump. Visit their website at https://www.kemsoracing.com/ to find the right pump for your engine and take advantage of their lifetime warranty. Your Johnson 5 HP will run like new again.