Check in order: manual override, float switch, wiring, then pump. 80 percent of failures are float switch or wiring.
Step 1 -- Test manual override
Every bilge pump has a manual override switch. If the pump runs on manual but not automatically, the issue is the float switch only -- skip to step 3.
Step 2 -- Check wiring and fuses
Inspect connections at the pump and fuse block. Look for corrosion, loose connectors, and blown fuses. Clean terminals and retest.
Step 3 -- Test and replace float switch
Manually lift the float mechanism -- if pump runs, switch is working but bilge water is not reaching it. If nothing happens, the switch has failed. Replacement costs $15-$25 and takes 10 minutes.
Step 4 -- Test pump voltage
Measure voltage at pump terminals on manual override -- should read 12V+. Correct voltage but no pump movement means the motor has burned out. Replace complete pump assembly.
Step 5 -- Test at the dock
Pour water into bilge to verify automatic activation. Do this test every spring commissioning regardless of whether issues were observed.
Sources & methodology: Repair procedures verified against ABYC standards and outboard manufacturer documentation. Difficulty ratings and cost estimates reflect typical DIY conditions. All guides reviewed for accuracy. Our editorial standards.
Frequently asked questions
Why is my bilge pump running constantly?
Usually means water is entering faster than the pump can remove it -- check all through-hull fittings after rain. Less commonly, a stuck float switch holds the circuit closed.
How often should I replace the float switch?
Every 3 years regardless of condition. At $15-$25 preventive replacement is far cheaper than discovering failure mid-season.