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Solved problems · Dinghy · Crew answer

Why is my outboard's tell-tale stream weak or stopped?

A weak or missing tell-tale stream means less cooling water is getting through, or the tell-tale outlet is blocked. Stop and check before the motor overheats.

Symptom

The small stream of water from the outboard's tell-tale outlet is weak, spitting or gone, sometimes with an overheat warning or reduced power.

Likely cause

Outboards pump cooling water through the lower unit with a rubber impeller. A blocked intake screen, weed or a plastic bag, a worn or damaged impeller, or salt and sand in the passages reduce flow. Often the cause is just the tell-tale outlet or its hose clogged with debris while cooling is still fine.

Stop now if

An overheat alarm sounds, the motor loses power, or you see steam. Stop the motor right away and don't restart until you've found the cause. Raise the motor and keep clear of the propeller while checking it, with the kill switch removed.

The fix, in short

  1. Stop and clear the intake. Shut the motor off, remove the kill switch lanyard, tilt the motor up and clear weed, plastic or mud from the water intake screens.

  2. Clear the tell-tale outlet. With the motor off, gently push a thin wire or pick into the tell-tale outlet to clear debris. If the stream comes back strong, the blockage was local.

  3. Check on the flush muff. With the motor in neutral and everyone clear of the propeller, run it on a flushing attachment or in a test tank and watch the stream. Removing the prop first is safest. Never run it without water. A weak stream with clear passages points to the water pump.

  4. Replace the impeller. Impellers wear, crack and lose vanes over time. Mercury dealers list a weak or inconsistent tell-tale and overheating as signs of a failing pump.

  5. Flush after salt water. Flush with fresh water after use in salt water to stop salt building up in the cooling passages.

Written by Sailor Cruiser crew. General guidance, not an inspection of your boat.

Equipment involved

  • Dinghy outboard: Outboard cooling system: water intake screens, water pump and impeller, cooling passages and tell-tale outlet

Related guides

Sources

Background reading we checked while writing this answer. The wording above is our own.

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