How To Prime A Fresh Water Pump On A Boat

All enjoy Marine life and boating adventures, circling round water. If your boat is designed for cruising or entertaining, it must include a steady fresh water system. It’s because you need to keep yourself 24/7 hydrated and well-set water supply system.

And that’s why boats end up having a fresh water pump. But setting up a pump is not the tag end. Issues arise when you don’t know how to prime a fresh water pump on a boat.

And the moment you skip being watchful, you find your boat pump is working no more. Yes, we all know it’s not that easy to fix any pump-priming troubles.

Before operating such pumps, you need to prime them first. But what if we say you can learn in no time? Your curiosity must be at its peak right now.

Let’s jump into the essentials first, and then you’re ready to top the task of priming boat pumps!

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What does boat pump-priming mean?

So, before you operate your pumping device on the boat, you need to introduce water into the pump. This process is known as pump-priming. You can expel air from inside the pump. Thus, the act of priming will improve the sealing of your boat’s pump parts.

In this act, the device stays filled with water first. The fluid forces the air or gas to escape out of the passage or ways the moment you pump. You can do it manually or automatically. Thus your boat fresh water pump keeps running.

Components of boat pump dealing with priming

Is your boat fresh water pump not working? Or you need to prime it manually? Before you know how to pump-prime in your boat, you need to understand the parts of the pump related to your task. These are:

  • Discharge Isolation Valve
  • Shutoff Valve
  • Foot Valve
  • Check Valve
  • Suction Isolation Valve
  • Air Vents
  • Rotating Impeller

Steps of priming water pump on your boat

So, if you’ve already invested in a water pump to install in your boat, wait a bit before you run it. It’s because you now need to prime the pump.

Let’s focus on the boat water pump troubleshooting and learn to prime the cruise device. Here is a broad overview of the steps of pump-priming.

If your boat pump has a suction supply at the top of the system

Step 1: Opening the suction pipe

First, you need to unlock the suction isolation valve. Open it slowly and carefully to avoid any damage risk.

Step 2: Filling the suction pipe and the boat impeller

Next, you need to keep your suction supply pipe, and the boat water pump impeller filled top to bottom with water. Otherwise, you may find it tricky to troubleshoot it.

Step 3: Opening the air vents

Now it’s your turn to provide better fluid flow. And for that, you need to open all the closed air vents near the suction and discharge pipes.

Step 4: Closing the air vents

When you find that the pumped fluid is finally flowing out, you’re done and ready to shut down the vents.

If your boat pump has a suction supply at the bottom of the system:

Step 1: Closing discharge isolation valve

It’s vital to keep an eye on the fluid discharge while you’re priming. That’s why we advise putting the lid on the discharge isolation valve and lock it well.

Step 2: Opening the air vent valves

Now you need expelling air so that your device pumps water well. Hence your task is to open all the air vents and air valves in the boat pump casing.

Step 3: Unlocking supply line valves

You’ll figure out that the outside supply line has a valve. Next, you need to keep it open till only water expels out from the vents and valves.

Step 4: Closing vents and supply line

Lastly, close all the valves and vents you had unlocked. Don’t forget the outer supply pipe. Please turn it off too.

Thus, priming your boat’s water pump is done! Still, if the boat fresh water pump won’t prime, replace fresh water pump on boat. In that case this SEAFLO self-priming water diaphragm pump
will definitely aid to steady your water supply system in boats.

Alert! Make sure your boat fresh water pump pressure stays moderate to avoid overflooding.

frequently asked questions

What’s a fresh water pump for boats?

A boat water pump is a pressurized water system or unit. It supplies you hot or cold water while riding on the board as you turn the faucet. The greatest thing about such marine boat pumps is that you’re the controller of the water flow. It’s no big deal to use it as per your water requirements.

What are the arrangements that ensure priming fresh water boat pumps?

The external arrangements are:

  • Manual priming
  • Prime with separator
  • Installing foot valve
  • Priming with jet pump
  • Prime with vacuum pump

When you’re not in need to prime?

If you’ve set up a self-priming pump, you no more need to prime it yourself. Again when you find the pump is submerged or at a lower level from the supply pipe, it requires no priming.

Why prime a marine pump on boats?

Priming allows you to maintain a proper water flow expelling the air or vapor out. Use a port filler to add fresh water to your boat pump. With water, the hose fills it at the dock and power the pump to run it the moment it fills up. Make sure not to flood the boat.

Final Say

Now you’ve learned how to prime a fresh water pump on a boat. Whether your pump is above or below the supply line, in both cases, fill the pump chamber with water.

Pour fluid through the exit spot. At the same time, keep stroking the handle upward and downward. It’s better to use foot valves with an external liquid source to prime the pump.

Knowing the tactics of priming, you won’t ever need to replace fresh water pump on boats. Get ready for a smooth water pump system while you’re enjoying boating.

Jack K. Pride
Jack K. Pride

Jack K. Pride is an accomplished author and a prominent figure in the boating community. With a passion for boats and a deep understanding of the maritime industry, he has been sharing his expertise through his compelling articles on

Known for his insightful and informative writing style, Jack's articles provide valuable insights, tips, and knowledge to boat enthusiasts worldwide. His dedication to the subject matter and commitment to delivering high-quality content makes him a trusted voice in the boating world.

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