Bilge pump running and how to leave it

Tally Ho · May 29, 2017

It looks like you have a separate float, and I am sure your pump will not clear the little bit of water out of your bilge. I usually pour a bucket of water in the bilge to test the float and pump.

You can also see at what level the float trips and turns on the pump, so in the future you know how much water in the bilge "is normal".

If you want all of the water out, use a shop vac and suck her dry. I do that sometimes too just to see if I have coming in (more than I expect).

Greg

mcrow33 · May 29, 2017

On my boat I have a bilge pump switch on my control panel that will turn the pump on as needed. There is also a float switch to run the pump if the bilge fills up even with the switch on off. It there is not enough water in the bilge sump for the pump to prime the pump with run but the little amount of water doesn't do anything. If you want to be sure the pump is working pour more water in the bilge and it should work. If you have a float switch you can trip that to see if the pump runs.

dlochner · May 29, 2017

Bilge pumps, like the one you have installed, only pump water, not air. The pump will pump water up and out but once the pump starts to suck air, it become ineffective. Any water that is in the hose will drain back into the bilge. The float switch should be mounted high enough that the pump does endlessly cycle due to the water draining back into the bilge. This can be prevented by placing a check valve close to the pump, but doing this is not without its own set of problems that can be worse than a little water left standing in the bilge.

A hand bilge pump or a sponge can take care of the remaining water.

dlochner · May 29, 2017

Randall Schmidt said:
thanks!

A related question... I'm told to leave the shore power hooked up and AC on to keep the batteries charged partly to enable the bilge pump to run and keep her from sinking in the event of unexpected water.

This means for me, it seems, I'd have to keep the DC power on and the bilge pump on and the pump never finishes running so it would burn out in short order. Do you leave your AC plugged in and turned on and if so why? If it relates to the bilge pump is there maybe a difference float switch that engages and is hot-wired to the battery in the event of catastrophic water levels?

If your boat has a galvanic isolator then it pays to leave it plugged into shore power to keep the batteries fully charged. This is good for the batteries. In the absence of a galvanic isolator on a boat that is connected to shore power the boat will be subjected to galvanic corrosion due to the connection to all other boats in the marina via the ground wire. (Except those boats that have a GI.) This is bad for the underwater fittings.

Bilge pumps are usually wired to an circuit that is always powered to prevent sinking or to at least slow down the process. You are correct that if the pump is always cycling, the battery will discharge and you will place undue wear on the pump. Keeping the boat connected to shore power will obviously allow the battery to remain charged and to allow the pump to keep running until it wears out.

Everything is connected. Monkey with one part and something else will happen!

Tally Ho · May 29, 2017

The pump should not run if there is no water in the bilge. If it is running dry, you need to check your float.

I am not sure how your set up is wired. On my boat, my bilge switch on the panel allows me to turn the pump on manually (overrides the float), or leave it on automatic, which relies on the float to trigger the pump.

I leave my AC power on for the battery charger ONLY when I leave the boat (I do not have a master DC switch). If there is beer in the fridge, I will leave that single DC breaker on (I hate warm ).

I would check out the float and the pump by pouring some water in the bilge and see if she turns on automatically. If so, that should give you some peace of mind. You may also want to check the pump for debris in the strainer, to make sure it is clear.

Good luck with it.

Greg

Benny17441 · May 30, 2017

The bilge pump will stop pumping water as soon as the level goes down far enough that the impeller starts sucking air. There will always be a remnant of water left in the bilge in addition to the water that was already in the discharge hose but flowed back into the bilge when the pump lost suction. Having a dry bilge is an elusive quest. The average boat has many gallons of water trapped in the hull stringers under the sole. It is very common for someone to dry the bilge just to come back a few minutes latter and find it has filled again. The average electric bilge pump is not a safety item as it would be easily overwhelmed by the smallest and continuous water intrusion but it is intended as a convenience item to pump out incidental water that collects in the bilge so you will not have to scoop it out. Bilge pumps are rated in Gallons Per Hour (GPH) as bench tested by the manufacturer under ideal conditions but in real life they only deliver around 30% of their rated capacity. Logic dictates that it is the smaller boats that need the largest pumps as the will fill and sink the fastest but in reality they would just perhaps at the very best buy some time in the hope that someone spots the problem.

dlochner · May 30, 2017

Benny17441 said:
Bilge pumps are rated in Gallons Per Hour (GPH) as bench tested by the manufacturer under ideal conditions but in real life they only deliver around 30% of their rated capacity.

Usually they are rated at zero head, meaning the pump doesn't account for lifting the water out of the bilge and up and out the outlet. The greater the vertical lift, the less effective the pump.

Bilge pump running and how to leave it

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