Why is my outboard engine not peeing cooling water and how do I fix it?

If your outboard engine stops peeing, the most common culprit is a simple blockage of salt, sand or a mud wasp nest in the tell-tale outlet hole. You can clear this instantly by poking a length of strimmer line or heavy monofilament fishing wire up the nozzle while the engine runs.

Clearing a Blocked Tell-Tale

The tell-tale acts as a visual indicator for the helmsman and diverts a tiny fraction of the cooling water. If the engine runs at normal temperature but the stream stops, the blockage sits right at the exit nozzle.

• Take a piece of 2 mm strimmer line or 80 lb monofilament fishing line and push it 50 to 100 mm up the outlet.
• Wiggle the line while the engine idles in the water or on flush muffs to dislodge the debris.
• Avoid wire coat hangers or drill bits, as these easily puncture the internal rubber tubing.

If poking the nozzle fails, remove the engine cowl and trace the rubber tube back from the plastic outlet to the engine block. Pull the tube off the nipple and inspect it. You can clear a stubborn plug of salt by blowing compressed air at 30 to 40 psi through the disconnected hose. Finding small chunks of black rubber blocking the tube means your impeller has shredded. Stop the engine immediately. Fragments are travelling through your cooling system.

Checking the Water Pump Impeller

If the tell-tale is clear but water flow remains absent, your water pump impeller has failed. The impeller is a rubber star-shaped wheel sitting in the gearbox. It pushes water up the pickup tube. Replace impellers every 100 hours or annually. They burn up and lose their vanes in seconds if the engine runs dry.

Before dropping the gearbox to access the water pump, disconnect the kill cord and remove the spark plug caps to prevent accidental starting. Dropping the unit requires removing four to six bolts with a 12 mm or 14 mm socket and uncoupling the shift shaft. Depending on the brand, disconnect the shift shaft via a locking nut under the carburettor or a small spline coupling halfway down the leg. Expose the pump housing and inspect the rubber impeller. If the vanes show cracks, missing sections or bends, fit a replacement. A genuine impeller from Yamaha, Mercury or Suzuki costs £20 to £40. If the stainless steel cup or wear plate is scored, buy the full water pump rebuild kit for £60 to £90 to ensure proper water pressure.