Honda BF20A-BF25A, BF25D-BF30D Outboard Motors Shop Manual., Page 251Get this manual
From P2-15 Stop the engine and check the water intake screen for cloggingIs the water intake screen clogged? Yes Remove the blockage
Start the engine and check whether the cooling water constantly flows through the check port with the engine idlingDoes the water constantly flow through the check port? Yes
Faulty water pump Clogged or damaged water tube Clogged check port
Idle in gear for few minutes to cool down the engineDoes the overheat indicator go off?
Buzzer does not stop and the overheat indicator stays ONCheck the thermostat (P9-21)Is the thermostat in good condition? Yes
Buzzer stops and the overheat indicator goes off
Normal (Overheat problem was removed)
L Buzzer stops but
the overheat indicator stays ON
Check the indicator (P16-201)