Determining Bilge Pump Size

Bilge pumps have ratings on lift, hose sizes and output hose sizes. Depending on what size hose you have and the distance you may have to increase the hose size. When I upgraded all my pumps (and added a few more) They were just 7/8" from the factory. They are now 1 1/8" as that was the required size per the bilge pump ratings for lift and distance. ( I do only have a little Bayliner Trophy) Thing looks like a New York City Fire Boat when they all go off together. Oh and yes they are all on auto switches.


One thing to remember and it does sound counter-intuitive is the smaller the space the larger the bilge pump needed, as they tend to fill faster.

I never thought of that! (not kidding) ... and makes plenty of sense.

The other thing to consider is the installation and wiring. If there are separate battery banks on the boat, it would be great to wire one or two bilge pumps to the house bank and the other to the aux bank.

The other thing is to check them regularly because FAILURE is their favorite past time. Keep the bilge clean and oil free and you have fewer problems with the pumps.

It's not uncommon to have a bilge pump turn on when the switch triggers ... and keep running until it burns itself out (failed switch) and drains the battery completely. Now none of the pumps connected to that battery bank will function.

I came within hours of sinking my Bertram 28 last year. A friend casually stopped by and said "the Bertram 28 looks a little low ... better check it out" ... water was already entering the rear scuppers ... bilge pumps and battery dead.

That is the reason I have 2 1100 gph in the bilge under the engine, a 500 in mid bilge and a 500 in the front bilge.

Of course with only 3 batteries I couldn't tell you how long they would run for. Long enough to beach it.

I have had to replace many Attwood floatswitches because they tend to stop when lifted to their highest point. Anyone here has the same experience?

We have also had a 40' powerboat sunk at her moorings because a floatswitch fastening screw came undone. The switch fell over to her side because of wave action, the switch activated and the pump drained the batteries. Rainwater filled the boat and took her down.

That will work nicely. Make sure you fuse the hot wire close to the battery and keep the pump wiring out of the bilge as long as possible. If you have to make splices, use high quality butt splices and cover them with the adhesive filled heat shrink so they are as waterproof as the wire itself.

I think a few minutes with Google will provide you with a lot of manufacturer advice as well as wiring diagrams and specifications for wire size and such.

Enjoy the project and what you learn from it will spill over (no oun intended) on a lot of other boat projects.

IMO there is only one bilge pump worth installing. And that is the one made by Ultra Safety Systems.

http://www.tefgel.com/contain.php?param=pumpswitch_price#

And while you are at it, don't forget to install a high water alarm system.

That looks like a neat compact package containing everything you need. I like the fact that you only attach the pump strainer to the bilge so that you can can remove the whole package from strainer with one hand and real fast for inspection.

I like to add indicator LED's that can be seen from the dock for the status of all critical items. Green LED means the item has power. Red LED means there is a problem (pump is running, No 120V, etc). That way I can verify that everything is set correctly when I am leaving the boat. Also I can instruct my neighbors or the marina that if they see any red LED's or missing greens to contact me. These circuits are relatively easy to add and a couple of LED's draw virtually nothing from a large battery. If the Nordhavn that sank had this monitoring setup chances are the owner or mechanic would have gone back and shut the doors.

Pascal

I cheated.
I both replaced my old pumps (they were still good, I actually put alligator clips on it and keep it for the skiff when dipnetting salmon) with larger ones AND added more.

Like I said before, I was Coast Guard, I watched people die in sinkings, I saw how fast them dang boats can sink.

Does that include the crash pump? How many gph is the crash pump?

You might want to rethink that. The last time I used a crash pump to save a boat from sinking, it was at the dock.

My mistake, I was using the term "crash pump" to describe the valve set up that allows you to use your engines as emergency bilge pumps.

I agree on not seeing the need to carrying a independent "crash/trash" pump if you never stray to far from land. But if you have the room they can come in handy from time to time.

Yes .. I was referring to the engine driven pump as the crash pump. Pascal ... do you include the engine driven pump in your 12k gph total bilge pump number?