How many bilge pumps

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swampu

swampu

Guru
Commercial Member
Joined
Jul 25, 2011
Messages
1,384
Location
USA
Vessel Name
Cajun Rose
Vessel Make
Biloxi Lugger
Well, I’ve been cleaning and getting ready for another great year of boating, I have been considering adding another bilge pump, I have one now, it’s a great pump and has never let me down. How many pumps does a 65’ Boat need, two/three? There were two engine driven pumps but they are inoperable, I had a 110v pump but I found out it was junk during my bilge cleaning fun. Well let the bullets fly
 
None, its wide open from stem to stern. There was a bulkhead about 1/3 of the way back from the bow. I plan on rebuilding that.
 
How many through hull ? I would ensure the number/capacity of the pump can cope with water ingress from these in case of need.

L
 
You should have at least one more pump than you need to overcome the largest leak you hope never to have,
 
Our boat came with one bilge pump located just above the stuffing box. All through hulls located in engine room. Limber hole through bulkhead is smaller diameter than through hulls. What were they thinking?

*Note to self* Install bilge pump of a size capable to keep up with broken through hull in engine room this year!
 
MurrayM said:
Our boat came with one bilge pump located just above the stuffing box. All through hulls located in engine room. Limber hole through bulkhead is smaller diameter than through hulls. What were they thinking?

*Note to self* Install bilge pump of a size capable to keep up with broken through hull in engine room this year!
Click to expand...



Same here. Our 42’ has two (what I would call small) Rule 2000s. Neither are place where the water collects and I worry able the true capacity and the ability for them to keep up should we clobber something with our props. I totally have the same note-to-self you do.

I plan to replace one with the small Whale IC that has the remote pickup to get to where the bow water puddles, then replace the one in the rudder area with a slightly larger one (the largest I can get that pumps thru a 1” tube). Finally add a new and much larger one between the motors that can really pump out quickly. That will a new thru hull and some decision making though.

Anyway, to the OP. The answer is that, within reason, you can never have too much. But don’t expect the factory setup to be sufficient. Always upgrade if you can. The advice from others is good. Find one that makes you feel good that it is there.
 
In an emergency, I would not rely on a 110V pump or an engine driven pump to keep my boat from sinking. They can be helpful, but DC is a more reliable power source.

There are really two services for bilge pumps: 1) To pump out minor leakages like from a prop shaft gland. 2) In an emergency pump out water as fast as it comes in or a least give you more time to find the source of the water and fix it.

The first type is often smallish, about 500 gph. The second type needs to be DC powered and big- 2,000 gph at least, maybe more for your 65' boat. This willl probably need dedicated DC circuit as it will draw 10-20 amps and big discharge hose. It's float switch should be mounted an inch or two higher than the smaller pump's.

David
 
Don’t forget that all these pumps lose significant performance when pumping uphill. I forget the numbers but a 2000 will only pump 2000 if the voltage is perfect, the outlet is horizontal and the intake is perfectly clear. Also, Seaflo are significantly cheaper than Rule so you can buy lots of them and wire them everywhere water might collect.

Consider also your strategy. If you find it difficult to move in your bilge or are not too handy, consider the bilge pump a delaying tactic (like fire extinguishers on fibreglass boats) to give to adequate time to abandon ship safely.
 
Looking at the charts which only go up to 40 to 45’ boats, which recommend 2000 to 4000 gph, I would be looking in the 6000 gph area. Make sure that they have wire for a 3% voltage drop and smooth bore discharge hose.
 
Personally to have experienced the usefulness of them I will say that you will never have enough and having more than enough cannot be bad thing :)

L
 
We have 3 on a 30 ft cruiser. 2 auto, 1 switched. Plus a manual pump. Plus a bucket. Rule #1: Keep the water out.
 
Our 42 foot boat has four 1500-2000 gph bilge pumps. As far as I know, this was the factory set up. All factory wired with switches and fuses outside of the 12v main buss.

We also have a 120 v portable crash pump.
 
Last edited:
And what about staged pump like a 800g/h then higher a bigger one and then a bigger one etc or is the opposite better? Or is all staged same better? Or I am just out of my mind :)

L
 
Generally the smaller pump goes lower as it can pump out to a lower level than a larger pump can. Mount the larger pump a bit higher so if the small pump can’t keep up the larger pump will come online and hopefully take care of it.
 
On our 60 fter we have 3 x 350gph with floats at different heights.
We also have 3 spares in parts locker.
Also, in place ready to go, just need plugging in and switch flicked are two of these that supposedly can do 1800gph
https://www.bunnings.com.au/ozito-350w-dirty-water-submersible-water-pump_p4816179

We could also divert deck wash and raw water pumps but I think if they were needed its probably time to think about stepping up into the dinghy anyway.
 
I have 3 x 2000 gph Rule pumps. The boat has 3 partial bulkheads, and there is one pump in the lazarette, one almost mid-ship in the ER and one further forward at the low point of the bilge. Alongside the latter is a 4 gph diaphragm pump which can run dry if needed but also gets water level down to about 1/4".

I would like a high capacity pump as well but have not sourced anything as yet. Perhaps something like this pool pump, 2" outlet, which is almost 8000 gph?
https://poolandspawarehouse.com.au/speck-pro-500-pool-pump-2-0hp-500lpm-1-5kw-5y-warranty.html
 
An interesting read on bilge pumps for a Navy 44'

Flooding vs bilge pumps

If a Navy 44 has a 1.5 in diameter hole at 3.5 feet below the water line (speedo thru-hull) it will experience a 82.4 gal/min influx of water.
Click to expand...
82.4 X 60 min = 4,944 gph

I know the Navy has a table for size of hole, depth of hole below water and inflow but I'm not able to find it.
 

Attachments

  • Flooding calcs.jpg
    Flooding calcs.jpg
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swampu said:
Well, I’ve been cleaning and getting ready for another great year of boating, I have been considering adding another bilge pump, I have one now, it’s a great pump and has never let me down. How many pumps does a 65’ Boat need, two/three? There were two engine driven pumps but they are inoperable, I had a 110v pump but I found out it was junk during my bilge cleaning fun. Well let the bullets fly
Click to expand...

I agonized a bit over this as well what made sense was looking at each compartment separately. On mine ive got 3 areas operated with bulkheads so each is tested different and separately. Engine room has the most because its got the shafts, two engines, two generators. So it gets two dc 3700gph dc on each end, one 2000gph ac, and both generator water intake can be flipped to draw water from inside as well. The mid ship gets a single 3700gph dc and the forward compartments a single 2000gph. A high water alarm in each zone, lights in the pilothouse if they turn on and a couple spares new in a box tucked away. All run on individual float switch with a manual switch as well. Total capacity was calculated from various articles linked from this forum as well as that formula above.

Just for redundancy you might want more than one.
 
I don't know the capacity of the pump you cited but the navy calcs say the inflow will be huge so it's going to take a monster of a pump.

I have no salvage experience so I have to trust the navy's calcs. I can't imagine trying to deal with a 10 inch hole! If I bash a hole that big in my boat I hope I'm stuck on the rock I just hit and can get things under control before the tide rises.
 
If you have space on your prop shaft(s) between the transmission and the packing, you can add a fastflow pump that works Well both forward and reverse. All you have to do is keep the props turning and find a place to run the vessel up on shallows in the event of a major hull breach. I would want an alarm placed below the pump level so you have an alert that there is a problem.
 
Salty has 5 2000gph 12v pumps between the 3 bilge sections and the 2 open top shower sumps. However, I doubt they'll do half that capacity after factoring in discharge head. Also have a 2" 120v emergency trash pump for when Murphy shows up. High water alarms in all 3 bilge sections.
Mor be betta!
 
I built four semi water tight compartments, each has a 2000gph dc pump. Half the pumps on engine start batt, other half on on house batt. Also have a shower sump and condensate drain sump that if submerged will pump some water.

Should be able to flood any of the four compartments and still stay afloat. For a while.

On a boat with a common bilge, I would want a minimum of two pumps hopefully with different DC power source. A smaller "keep dry" pump mounted low, and a big one mounted higher up.
 
danderer said:
I felt pretty comfortable with my current setup: 4 pumps with a total nominal capacity of 8500 GPH on a 40' boat.

However, when changing the depth transducer this week I realized a failure of even that single small fitting would overwhelm all my pumping capacity and sink the boat.

The math is pretty straightforward. Even assuming all 4 pumps work correctly my effective pump rate would probably be 4000-5000 GPH. The transducer fitting, a 2" hole located 2' below the waterline will admit about 6700 GPH.

Absent quickly acquiring more pumping capacity or stemming the flow, the boat is going to the bottom.

That is just an example, but my takeaway is the importance of the advice above: Be ready to deal with flooding situations by limiting the ingress of water--don't just expect to rely on your pumps.
Click to expand...

I still feel the same way about this.
 
As long as you can get access to the hole, one of these

108-150110.jpg


Would make the pumps job A LOT easier.
 
This is an interesting discussion. What are the most likely flooding causes? Through hull failure, raw water cooling hose failure, shaft pulled out of the stern tube.? Using the navy calcs for my boat I am drastically 'under pumped'.

Regarding the pumps they are all 12 V DC pumps. My batteries are low in the engine room, when the batteries drown the pumps stop.
 
How big is the leak ? Id say the same as a length of sting.
My boat just passed insurance survey with 100% :thumb:its 32 IG .
The insurance company required 2 x 2000gph pumps which it has . So wouldn't you think they have some idea of whats needed to protect there side of the policy ???.
I've seen a 3 inch hole in the bottom of a timber 40' ferry and it was uncontrollable even with a 12hp fire pump on the dock .
 
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