Honda Outboard Engine Temperature Warning — Fix Guide

What Does This Error Mean?

Honda's engine temperature warning lamp (red thermometer icon) lights when engine temperature exceeds safe limits.
The PGM-FI ECM may also reduce RPM automatically.
Pull throttle back to idle and check the telltale water stream coming out of the engine cover.
If no water flows, the cooling intake is blocked or the impeller has failed — head back at idle speed.

Affected Models

Honda BF40-BF250
Honda BF60-BF115
Honda BF150-BF250
Honda iST-equipped models

Common Causes

Water intake blocked by weeds, plastic, or sand
Impeller in the water pump worn or damaged
Thermostat stuck closed
Cooling passages restricted by salt buildup
Telltale tube blocked but cooling itself fine

How to Fix It

Reduce throttle to idle immediately.

Pull back to idle when the warning lamp lights.
Honda's ECM may have already reduced RPM — go further yourself.
Continued running at high RPM with poor cooling damages cylinder walls and pistons within minutes.
Check the telltale stream.

Look at the water stream coming out of the back of the engine cover (telltale).
Should be a steady stream, not just drips.
If missing or weak, water isn't flowing through the engine.
This confirms overheat is real, not a sensor fault.
Inspect the water intake.

Lift the engine partway out of the water if conditions permit.
Look at the water intake holes on the side of the gearcase below the cavitation plate.
Plastic bags, weeds, fishing line — clear anything visible.
This fixes a high percentage of overheat warnings.
Run at idle until cooling resumes.

Once intake is clear, run at idle and watch the telltale.
Water should resume in 30 seconds.
If it doesn't, the impeller is damaged.
Head back to the dock at idle — don't push throttle.
Running on a damaged impeller compounds the problem.
Have the impeller replaced after a serious overheat.

Even if the engine survived, sustained overheat damages the impeller from running dry.
Honda Marine certified mechanics replace impellers as routine annual service.
Cost: 150–350 USD typical.
Don't skip — running on a damaged impeller invites larger failure.

Frequently Asked Questions

Will the warning damage my engine?

If you reduce throttle quickly and find the cause, no.
If you keep running at speed for minutes with the warning active, yes.
Cylinder walls and pistons take damage from heat soaking.
The warning's purpose is to tell you to stop and fix the cooling — listen to it.

How often should the impeller be replaced?

Every 2–3 years for normal use, annually for boats stored seasonally.
Honda specifically recommends replacement at 100 hours or annually.
Impellers dry out and crack when sitting in air — that's why annual replacement is recommended for seasonal boats.
Cheap part, expensive consequences if neglected.