Shurflo Boat Water Pumps: Aqua King II, Washdown and Macerator Guide
Shurflo, part of Pentair, makes most of the small pumps on a boat: the fresh water pump that pressurizes the faucets and shower, the washdown pump on deck, livewell pumps, macerators and bilge pumps. They look alike on a parts list, but each line is built for a different job. This guide explains which Shurflo pump does what, using Shurflo’s published specifications for the marine models we carry, and how to pick the right size or replacement.
The short answer
- Water at the faucets and shower: an Aqua King II fresh water pump, sized by how many fixtures you run at once.
- Hosing down the deck, the fish box or the anchor chain: a Blaster II or Pro Blaster II washdown pump.
- Emptying a holding tank or a fish box: a Shurflo macerator pump.
- Winterizing, oil changes and moving liquids: a Shurflo utility pump.
Aqua King II fresh water pumps
The Aqua King II is an automatic demand pump: a pressure switch starts it when you open a faucet and stops it when you close it. Shurflo lists the same core features across the line: self-priming up to 6 feet, able to run dry without damage, a built-in check valve, an adjustable pressure switch, a sealed, corrosion resistant motor, and thermal and ignition protection. The Standard has an internal bypass that Shurflo says prevents rapid cycling. The Premium and Supreme use a built-in mechanical bypass that lets them run at low flow with little cycling and without an accumulator tank, and they come with an inlet strainer and 1/2″ hose barb fittings.
| Aqua King II model | Flow | Replaces | Voltages we carry |
|---|---|---|---|
| Junior | 2.0 GPM | 2901 | 12V |
| Standard (12V, 24V) | 3.0 GPM | 3901 | 12V and 24V |
| Premium (12V, 24V) | 4.0 GPM | 4901 | 12V and 24V |
| Supreme (12V, 24V) | 5.0 GPM | 5901 | 12V and 24V |
The “Replaces” column is Shurflo’s own cross-reference, so if your old pump is a 2901, 3901, 4901 or 5901, the matching Aqua King II is the direct replacement. On the 24V models Shurflo lists a 55 PSI shut-off and a current draw of 3.8 amps for the Standard, 5.3 amps for the Premium and up to 7 amps for the Supreme.
Choosing the size. Flow is what matters. A small boat with one sink needs far less than a cruiser where someone showers while the galley faucet runs. Shurflo designed the Premium and Supreme for boats with multiple fixtures and describes them as giving “just like home” shower pressure.
Washdown pumps
A washdown pump feeds a hose on deck with raw water for cleaning the deck, scaling fish and rinsing mud off the anchor chain as it comes up. The Blaster II delivers 3.5 GPM, and Shurflo lists 45 PSI shut-off on the 24V version. The Pro Blaster II steps up to 4.0 GPM (Deluxe) and 5.0 GPM (Ultimate), with an inlet strainer, fittings and nozzle included; Shurflo lists 60 PSI on the 24V Ultimate. For a complete setup, the Pro Washdown Kit II (Deluxe 4.0 or Ultimate 5.0) adds a raw water strainer and a 25′ coiled hose.
Macerator, utility, livewell and bilge pumps
Macerator pumps empty holding tanks and fish boxes. Shurflo’s macerator moves 13 GPM with a dual blade design and can run dry. We carry it in 12V, in 12V with a 180 degree port and as a self-priming 24V model with a 1-1/2″ inlet.
Utility pumps are small self-priming pumps for winterizing, oil changes and liquid transfer, rated at 1.5 GPM. The Premium Utility Pump comes with an 8′ cable and battery clips; the Standard is the simpler version, and there is also an oil change pump with a 3.5 gallon bucket.
Livewell and bilge pumps are separate lines: the Bait Sentry (500, 800 and 1100), the High Flow Livewell (1500 and 2000 GPH) and the Pro Baitmaster II for livewells, and the 700, 1500 and 2000 GPH bilge pumps.
Repair instead of replace
When an Aqua King II or Pro Blaster II loses pressure, the pump head is often the worn part, not the motor. Shurflo sells replacement pump heads and upper assemblies by series: the 4148 pump head kit for the Aqua King II Premium 4.0, the 4158 kit for the Supreme 5.0, and the upper assembly that fits the Premium 4.0 and Supreme 5.0 in 12V and 24V. Check the model number on your pump label before ordering.
Which Shurflo pump replaces my old 2901, 3901, 4901 or 5901?
Shurflo lists the Aqua King II Junior (2.0 GPM) as the replacement for the 2901, the Standard (3.0 GPM) for the 3901, the Premium (4.0 GPM) for the 4901 and the Supreme (5.0 GPM) for the 5901. Match the voltage of your boat, 12V or 24V, when you order.
What size fresh water pump do I need on a boat?
Size it by how many fixtures run at the same time. A small boat with one sink is well served by a 2.0 or 3.0 GPM pump. A boat with a shower, a head sink and a galley faucet that may run together is better with a 4.0 or 5.0 GPM Aqua King II Premium or Supreme, which Shurflo designed for multiple fixtures.
Can a Shurflo pump run dry?
Shurflo lists dry run capability for the Aqua King II fresh water pumps, the Blaster II and Pro Blaster II washdown pumps and its macerator pumps, so a short run with an empty tank will not damage them. Running dry still wastes battery power and wears the pump, so turn the pump off at the breaker when the tank is empty.
Why does my boat water pump keep cycling?
If the pump starts and stops by itself with every faucet closed, the system is losing pressure. The usual causes are a small leak in a fitting, faucet or water heater valve, or a worn check valve in the pump head. On pumps without a bypass, rapid cycling at low flow can also be normal; the Aqua King II Standard, Premium and Supreme use a bypass to reduce it.
Shop Shurflo pumps
Every pump above is in our Marine Pumps category. Not sure which pump you have or need? Send us a photo of the label on your old pump or call (786) 277-2596 and we will match it for you.