How to Install a Washdown Pump

In this example of how to install a washdown pump I will be replacing a below deck raw water pump on a 25-foot Grady White center console. The only symptom supplied by the operator was, “The system popped the circuit breaker when I tried to use it”.

With these symptoms I suspected a locked-up pump. The first thing I did to troubleshoot the system was go to the pump and measure the input voltage. To do this I had to remove a deck panel and then pull apart a wire harness connector near the pump.

johnson pump aqua jet washdown pump

The pressure hose, seen on the left, is secured with padded stainless steel cable clamps. The pump has its own pressure switch to turn it on when demand is sensed. It is mounted to the vertical bulkhead with shock absorbing bushings.

Voltage here was good, just a couple tenths of a volt below battery voltage.

With this noted and the pump looking pretty corroded it was obvious the pump needed replacement.

Of course, on a boat when you start to take things apart other issues become readily apparent. Our how to install a washdown pump tutorial would not be complete with mentioning this reality.

In this case the issues noted were minor, the area needed a general cleaning and a few wires needed to be re-secured to the bulkhead.

I selected an Aqua Jet WD 3.5 as the replacement unit on this installation. On my 25-foot Contender where a little more flow was desired I have an Aqua Jet WD 5.2 installed on a freshwater washdown system. Several years ago I reviewed these two pumps as well as a number of others for a well-known marine publication and rated both highly.

Since the old pump and the new one I had chosen were not identical a few things needed to be reworked. First off, the new pump did not fit the same mounting holes as the old. I was able to use one old hole and then had to drill three new ones to bulkhead mount the pump. I filled the three remaining open holes as well as any others I could see with sealant to prevent any water intrusion.

I found the washdown system hoses to be a little stiff but still in serviceable condition. The pressure hose only required a little rerouting and re-securing. I took a section of the old inlet hose and cut it to fit between the seacock and the new pump filter inlet. All hoses were clamped with stainless steel clamps and secured solidly to nearby structure.

The wiring to the area was in good condition with no corrosion noted on the conductors. I simply reconnected the wiring using crimp-on heat-shrink butt connectors. Wires were then bundled and tie-wrapped securely.

Important How to Install a Washdown Pump Tips

    • Only use marine grade hose when plumbing any type of pump on a boat. The hose must have some sort of wall structure that prevents crushing.
    • Use marine grade stainless steel clamps to secure a hose to a fitting. Generally all below the waterline connections should be double clamped when possible.
    • Most small boat hose fittings are not designed for double clamping and should only be fitted with a single clamp. Using two clamps on a fitting designed for one can damage the hose.
    • Make sure the pump is mounted securely, all wiring is bundled and tie-wrapped as high out of the bilge as possible, and all plumbing is secured with appropriate clamps.
    • Any pump requiring a raw water source must be fitted with a seacock shut-off as close to the inlet as possible. The valve should be marine rated, lever controlled, and closed with a quarter turn of the handle.