Most boats that sink do it at the dock, not underway. BoatUS says 69% of sinkings happen dockside or on a mooring (BoatUS). The bilge pump and float switch are your last line of defense, so it pays to check them before you leave the boat for a week or a storm rolls in.
This is a general explainer. Always follow your pump’s owner’s manual, and have a qualified marine technician handle wiring or below-waterline work.
Water sinks boats, not bilge pumps
A pump that runs often is telling you water is getting in. BoatUS found that in 50% of dockside sinkings, the water came through leaks at underwater fittings such as stuffing boxes, bellows, failed hoses or hose clamps, sea strainers and drain plugs (BoatUS Foundation). Rain, snow and sleet account for another 32% of sinking claims (Sail-World, citing BoatUS).
A 5-minute bilge check
- Clear the bilge. Leaves, construction debris and hair can clog a pump or jam the float (BoatUS Foundation).
- Test the float switch. Lift the float by hand, or add water, and confirm the pump starts and stops on its own. BoatUS suggests adding enough water to trigger the switch, then sponging out the rest (BoatUS Winterizing Guide).
- Check that the pump works with the panel off. BoatUS recommends an automatic bilge pump that is fused and wired to run even when the main panel switches are off (BoatUS Winterizing Guide). If you’re not sure how yours is wired, ask a qualified marine electrician.
- Look at hoses and clamps. A rusted clamp can let a hose vibrate loose (Power & Motoryacht).
- Keep the battery charged. A pump can’t help once its battery is dead.
- Clear scuppers and deck drains so rainwater leaves the boat instead of filling the bilge.
Sizing a replacement pump
Pump ratings in gallons per hour assume no lift. Most pumps have to push water up several feet to the outlet, so real output is lower than the label (BoatUS). When in doubt, go a size up and check your boat manufacturer’s specs.
Parts SCN Marine carries
Automatic bilge pumps
- Johnson Pump 500 GPH automatic, 3/4 in. hose, 12V (current season deal, one per customer)
- Attwood Sahara MK2 S500, 500 GPH, 12V automatic
- Attwood Sahara MK2 S800, 800 GPH, 12V automatic
- Attwood Sahara MK2 S1200, 1200 GPH, 12V automatic
- Rule 500 GPH bilge pump kit with float switch, 12V
Float switches and controls
- Rule-A-Matic float switch (35A)
- Rule SuperSwitch float switch (37A)
- Attwood automatic float switch, 12V and 24V
- Johnson Pump 3-way bilge control, 12V
Service parts
Not sure which pump or switch fits your boat? Call or text Sean at (772) 353-8158 with your boat’s make, model and current pump, and he’ll help you find the right part.