How to Rebuild a Johnson 6HP Outboard Carburetor

Years of use take their toll on older outboard carburetors, and our 1978 Johnson 6HP 6R78B engine's carburetor was no exception. 

This guide shows you step-by-step how to disassemble and rebuild the carburetor on a small outboard engine, including removing, dismantling, rebuilding and reinstalling the carburetor.

Johnson 6HP outboard motor

Watch the carburetor rebuild video above to better understand the processes involved, and print this guide to use as a checklist while you work. Use our Johnson 6HP carburetor parts diagram to see how all the components come apart and fit back together again.

Tools and Parts Needed - Johnson 6HP Carb Rebuild 

Tools

  • Ratchet and extensions
  • 8mm socket
  • 12mm wrench
  • Flathead screwdriver
  • Pick tool
  • Nylon brush
  • Brass-bristle brush
  • Impact driver
  • Small punch tool

Parts

Removing the Carburetor From a Johnson 6HP Outboard

Step 1. Remove the fuel line from the left side of the carburetor.

Johnson 6HP outboard carburetor removal

Step 2. Remove the choke lever from the rear of the carburetor by carefully prying the rubber O-ring off the retaining pin and removing the pin.

Johnson outboard carburetor removal

Step 3. Remove the recoil starter assembly by taking off the four 8mm bolts and lifting the assembly out. With the assembly removed, take off the guide pin and the lower retaining bracket.

PRO TIP: You don't need to remove the starter assembly's cord, just move the assembly out of the way and let it rest there.

Johnson 6HP carburetor rebuild removal

Step 4. Remove the throttle linkage by taking off the single flathead screw. 

NOTE: Be very careful not to allow the small washer that's on the carburetor side of the screw to fall off into the cowling because it'll be very hard to retrieve.

Johnson 6HP carb removal

Step 5. Remove the carburetor assembly by taking off the two 12mm bolts holding it to the motor, and remove the old carburetor mounting gasket.

Johnson 6HP outboard engine carb removal

Step 6. Thoroughly clean the outside of the carburetor assembly with contact/brake cleaner and a nylon brush. This minimizes the chances of dirt or contaminants getting into the carb when you rebuild it.

Watch the clip below to see the carburetor removal segment of our Johnson 6HP outboard carburetor rebuild video.

Disassembling the Carburetor From a Johnson 6HP Outboard

Step 1. Remove the float chamber from the bottom of the carburetor assembly by taking off the five flathead bolts. Remove the float chamber drain bolt, then remove and discard the old float chamber gasket.

PRO TIP: To prevent stripping the carburetor bolt heads, try breaking the threads loose by placing a screwdriver on top of the bolt and tapping it with a hammer to shock the threads. If shocking the threads doesn't break them loose, you'll need to use an impact driver to free them.

Johnson 6HP outboard motor carb repair

Step 2. Use a small punch tool to remove the hinge pin that holds the float assembly, then remove the float and the small float valve attached to it.

Johnson outboard motor carb rebuild

Step 3. Unscrew and remove the high-speed nozzle jet, the slow-speed needle jet and the float seat.

PRO TIP: Be careful when unscrewing these parts, as they are made of brass and can shear if too much torque is applied to them.

Johnson 6HP outboard carburetor parts

Step 4. Thoroughly clean the inside of the carburetor assembly and the float chamber with contact/brake cleaner and a brass-bristle brush

Johnson 6HP outboard carburetor assembly

Step 5. Blow the various channels and jet housings in the carburetor assembly and float chamber with compressed air to remove any last particles of dirt and debris.

Step 6. Inspect the high-speed and slow-speed jets for pitting or corrosion, and replace them if necessary. Otherwise, thoroughly clean them if they're still usable.

Watch the clip below for the carburetor disassembly segment of our Johnson 6HP outboard carburetor rebuild video.

Rebuilding the Carburetor From a Johnson 6HP Outboard

Step 1. Reinstall the drain bolt into the float chamber using the new drain bolt gasket included in the carburetor repair kit

Johnson 6HP outboard carb rebuild parts

Step 2. Reinstall the high-speed nozzle jet, being careful not to overtighten it, then place the new nozzle gasket (included in the kit) over it.

Step 3. Install the new float seat and sea gasket (both included in the kit).

Step 4. Install the new float valve onto the new float assembly (both included in the kit), then install them into the carburetor, making sure the float valve is sitting in the float seat. Install the new hinge pin (included in the kit) to secure the float and valve assembly in place.

Johnson 6HP outboard carb float valve assembly

Step 5. Install the new float chamber gasket (included in the kit), and reinstall the float chamber onto the carburetor assembly.

Johnosn 6HP outboard carb rebuild components

Step 6. Reinstall the slow-speed needle jet and its retaining nut.

Johnson outboard engine carb rebuild

Watch the clip below to see the carburetor rebuilding segment of our Johnson 6HP outboard carburetor rebuild video.

Reinstalling the Carburetor Into a Johnson 6HP Outboard

Step 1. Install the new carburetor mounting gasket (included in the kit) to the side of the powerhead.

Johnson outboard motor carb rebuild 6HP

Step 2. Reinstall the carburetor assembly, reattach the throttle linkage, reinstall the recoil starter assembly, reattach the choke lever, and reattach the fuel line to the carburetor and you're done.

Johnson 6HP outboard carburetor rebuild

Watch the clip below to see the carburetor reinstallation segment of our Johnson 6HP outboard carburetor rebuild video.

 

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