Guide 08 stop, check, call
Engine overheat alarm
Slow down, find out whether cooling water is flowing, and do not open a hot system.
Stop first
- Bring the engine to idle and, when it is safe to do so where you are, shut it down as your engine manual directs.
- Do not open a hot pressurised cooling cap. Let it cool first, as the engine maker warns.
- If you lose propulsion near hazards, anchor if you need to, and call for help on VHF Channel 16.
Checks an owner can do
- Raw-water cooled: is water coming out of the exhaust or telltale as usual?
- Look for a plastic bag or weed at the water intake if you can see it from the boat; never go in the water with an engine running.
- Raw-water strainer: only if your manual describes it, and only with its seacock closed first. If the seacock will not close, stop and call a technician.
- Coolant level (closed systems): check it only when cold, against the marks your manual describes.
Call a certified marine technician when
- No water flow after the checks above (pump impeller, heat exchanger, exhaust elbow and hoses are technician work on most boats).
- Any seacock or through-hull that is stiff, leaking or will not close.
- The alarm comes back after cooling down.
Sources
- Your boat's, engine's and appliance makers' owner's manuals, The manufacturer
- Boater's Guide: VHF MAYDAY procedure (PDF page 47), U.S. Coast Guard Boating Safety Division
Reviewed 2026-10-08. Your manufacturer's instructions come first wherever they differ from this page.
Keep a record and brief your technician
Log this problem on your boat with the checks above as a checklist. Tick what you have done, then print a one-page technician brief: the boat, engine hours, what happens, what you already checked and the boat's recent work. When it is fixed, it goes into your maintenance log.
The technician brief is part of Skipper: $1.95 a month or $19.50 a year. Free during preview. Pricing