Why Is My Outboard Overheating?
Weak tell-tale stream, alarm, or steam: what it means.
An overheating outboard needs attention right away. Running hot can warp the cylinder head, damage pistons and ruin the engine. Throttle back to idle, check the tell-tale stream, and do not keep running at speed with the alarm on.
Check the tell-tale first
The tell-tale (or "pee stream") is the small stream of water from the side or back of the engine. It shows water is moving through the cooling system. If it is weak or missing:
- The tell-tale hole may be blocked. Salt, sand or insects clog the small outlet. With the engine off, clear it with a small piece of wire. If a strong stream returns, that was the problem.
- The water pump impeller may be worn. The most common real cause. See when to replace an impeller.
- The water intake may be blocked by a plastic bag, weed or marine growth on the lower unit.
Other causes
- A stuck thermostat keeps water from flowing through the head. Salt and corrosion make them stick.
- Salt buildup in the cooling passages, usually from skipping the fresh water flush. See how to flush an outboard.
- A faulty temperature sensor can set off the alarm when the engine is not hot. A diagnostic scan shows the real temperature reading.
- Running the engine too high on the transom, or in very shallow water, so the intake sucks air.
When to call us
If clearing the tell-tale does not bring a strong stream back, or the alarm keeps sounding, stop running the engine and book a diagnostic visit. We come to your boat anywhere on Oʻahu and can replace the impeller and thermostat on the spot when parts are on hand.
