- Action: To Do List item A0155 – Obtain replacement water pump.
- Completed: 17 September 2018
- Cost: $177.90
The criteria for the replacement water pump was very simple - we wanted a pump of the same capacity with positive reviews/reputation. After researching the internet, we selected a SHURflo 4048 High Flow Water Pump part number 4048153E75 ($154.49). This new pump was identified as being designed to replace the 4900 Smart Sensor series product - the old defective pump. Downloaded the Installation & Operation Manual from the manufacture's website and reviewed it.
The pertinent information gleamed from the documentation was:
- Flow Rate: GPM/LPM 4.0 GPM [15 LPM] - same as old pump.
- Shut-Off Pressure: 55 PSI [3.8 BAR] - same as old pump.
- Leads: 14 AWG, 14 ¾” [37 cm] Red +, 13” [33 cm] Black - kudos to manufacture for disclosing this - important for wire splice size selection.
- Fuse: 15 Amp Recommended - same as old pump.
- Amps (Max.): 10 - important for determining connecting wire size.
As the pump power wire was to run from the 12V DC circuit breaker panel to essentially the same location under the galley sink - the estimated length of the wire run was about 12 feet plus 1 foot for the pump wiring pigtail. We decided to replace the old wiring since the old wires were not marine rated, not the correct size, and were assembled from three separate pieces of wire joined together with butt splices - this increases overall circuit resistance. We would use a continuous run of UL1426 marine rated wire.
To determine the actual size of the wire needed we used the following formula (ref 46 CFR §183.340.(p) and ABYC E-9.14.e.(4)). The 3% allowable voltage drop, instead of 10%, was selected since DC motors operate more efficiently at their rated voltage.
CM = (K x I x L) / E
Where:
CM = Circular mil area of conductor.
K = 10.75 (constant representing the resistivity of copper).
I = Load current in amperes.
L = Length of conductor from the positive power source connection to the electrical device and back to the negative power source connection, measured in feet.
E = Maximum allowable voltage drop at load in volts (For a three percent voltage drop at 12V, E= 0.03 x 12 = 0.36).
We used the value of 10.75 for K, 10 amp current draw at 12V for I, 26 feet (13ft x 2) for L, and 0.36 as the 3% voltage drop for E.
CM = (10.75 x 10 x 26)/0.36 = 7,763.9 which equates to 10 AWG since it has a CM of 10,380; ref ABYC E-11 (7/15) Table XI. Note - 12 AWG has a CM of 6,530 which is smaller than the calculated value, so the next larger AWG size is needed.
The following picture illustrates the electrical installation diagram.
The following items were purchased to support this installation.
| P/N | Item | Q | Each | Total |
| 4048153E75 | Shurflo 4048153E75 Electric Water Pump | 1 | $154.49 | $154.49 |
| 10/2RY50FT | 10/2 AWG Duplex Tinned Marine Wire, Red/Yellow 50 Feet | 12 | $1.12 | $13.44 |
| 320203 | 16-14 to 12-10 AWG Step-Down Heat Shrink Butt Connector (3 each) | 1 | $6.17 | $6.17 |
| 12-10 AWG #8 Ring Heat Shrink Splice | 1 | $0.25 | $0.25 | |
| 12-10 AWG #10 Ring Heat Shrink Splice | 1 | $0.25 | $0.25 | |
| 2-inch Stainless Steel Screws | 4 | $0.45 | $1.80 | |
| Cable/Tie Straps | 15 | $0.10 | $1.50 | |
| TOTAL | $177.90 |
On 17 September 2018, removed the old wiring and the defective pump.
Installed the new water pump, under the galley sink against the vertical wall with four Philips head wood lag screws. Routed 10 AWG duplex wiring from the 12V DC circuit breaker panel, 15 AMP circuit breaker, to the water pump and connected the wires with marine rated splices. New water hose and clamps were also installed. Pump worked quietly and shut off automatically under pressure properly.
