Mercury Tracker 40 2-Stroke Fuel Pump Rebuild 

Rebuilding the fuel pump on a Mercury Tracker 40 doesn’t take much. All you need are some basic tools (ratchet, extensions, screwdriver) to disassemble and reassemble it. 

As far as parts go, Mercury has a fuel pump diaphragm kit that has everything you need to do this project, which is part of our complete outboard engine rebuild. 

Watch the video above and follow the steps below to rebuild the fuel pump on a Mercury 40HP two-stroke outboard.

NOTE: We’re rebuilding this outboard motor from the crankshaft up. You don’t need to take your entire motor apart to get to the fuel pump. 

Step 1. Disconnect the three fuel lines connected to the fuel pump, then release the bolts that hold the fuel pump in place and pull the pump off the engine.

PRO TIP: Before you disassemble the fuel pump, use a marker to help you figure out what orientation it needs to be in when it’s remounted.

Step 2. Remove the bolts from the fuel pump assembly, then use a flat-blade screwdriver to pry it apart.

Step 3. Remove the components that make up the fuel pump assembly, including all gaskets and diaphragms.

NOTE: Use our Mercury 40 exploded parts diagrams for reference of how things came apart and back together again.

Step 4. Remove the check valves. 

NOTE: The Mercury 40 outboard we worked on is a later model unit which has plastic or nylon check valves. If your outboard is an older model, you may have to drill out for a larger pin set for the little retaining clip to go back in.

Step 5. Pop the springs and caps out by pushing in on the center pin to release them.

Step 6. Install the new check valves and press them in. 

NOTE: According to the service manual, when you push the check valve in, it'll stop and then you have to break off the end. However, one of ours (the one on the left pictured below) went in like it was supposed to, and flowered out the other end to where it holds it in place, so there was nothing to break off. 

Step 7. Install the new spring and the plastic seat for both sides of the fuel pump.

NOTE: One side has a smaller plastic seat and spring. 

Step 8. Reassemble the fuel pump assembly in the same order it was before you took it apart (diaphragms, rear plate, mounting bolts, etc.).

Step 9. Install the top outer gasket over the fuel pump assembly, then mount the fuel pump back onto the engine block. Next, tighten the bolts by going around a couple of times to compress all those gaskets down to where they seal up.

Step 10. Reconnect the three fuel lines back up to the fuel pump and you’re done. 

Watch the playlist above for our complete series on Mercury 40 Tracker two-stroke outboard repairs.