A properly installed bilge pump helps remove standing water from the lowest part of a boat’s bilge. Correct pump placement, discharge-hose routing, wiring, circuit protection, and routine testing are all essential for dependable performance.
This guide explains how to install a current Attwood Tsunami Mk2 manual bilge pump and covers the general principles that also apply to many earlier Tsunami cartridge pumps. Always follow the instructions supplied with your exact pump because fuse sizes, outlet configurations, wiring requirements, and mounting features vary by model.
Important: The original version of this guide covered legacy Attwood 4606, 4608, 4612, and 4613 Series pumps. Current Tsunami Mk2 models use different model numbers and updated installation features. Owners of legacy pumps should use the instructions and specifications provided for their original model.
Bilge Pump Installation Safety
WARNING: Read the pump manufacturer’s complete instructions before beginning installation. Disconnect the boat’s power source before installing, wiring, cleaning, or servicing the pump. Remove the boat from the water before using 120-volt AC power tools.
Do not use a bilge pump to remove gasoline, oil, fuel, solvents, or other flammable liquids. Use only marine-grade electrical components and the fuse size specified for your exact pump model. Improper wiring or circuit protection can create a risk of equipment damage, electric shock, personal injury, or fire.
Bilge pumps are designed to remove standing bilge water. They are not intended to stop flooding caused by hull damage, failed plumbing, severe weather, or another source that introduces water faster than the pump can discharge it. A bilge pump is an important part of a boat’s water-management system, but it is not a substitute for maintaining the hull, seacocks, hoses, clamps, and other through-hull components.
About Attwood Tsunami Mk2 Bilge Pumps
Current Attwood bilge pumps include manual and automatic configurations for different boat sizes and pumping requirements. The Tsunami Mk2 manual series features a removable cartridge, external mounting feet, rotatable outlet options, and an X-Air impeller designed to help clear trapped air from the pump and discharge plumbing.
The Attwood Tsunami Mk2 500 GPH manual bilge pump is a 12-volt pump intended for smaller bilge-pumping applications. It can be operated from a manual control switch or paired with a compatible automatic control device when installed according to the applicable instructions.
Attwood Tsunami Mk2 Fuse Requirements
Use the fuse rating specified for the exact pump. Installing an oversized fuse can leave the wiring and equipment inadequately protected, while an undersized fuse may open during normal operation.
| Tsunami Mk2 Model | Rated Voltage | Specified Fuse Size |
|---|---|---|
| 5606-7 500GPH | 12-volt DC | 3 amps |
| 5608-7 800GPH | 12-volt DC | 4 amps |
These ratings apply to the current Tsunami Mk2 models listed. Do not use this table to select a fuse for a legacy Tsunami pump or another Attwood model. Check the pump label and current manufacturer documentation.
Tools and Materials Needed
The exact materials depend on the pump model, outlet size, existing plumbing, hull construction, and whether the pump will be operated manually or automatically.
- Attwood Tsunami Mk2 bilge pump
- Manufacturer-specified stainless steel mounting fasteners
- Drill and appropriately sized pilot bit
- Marine-grade, smooth-bore bilge hose in the correct inside diameter
- Marine-grade stainless steel hose clamps
- Compatible through-hull fitting
- Marine sealant approved for the hull and through-hull materials
- Marine-grade wire sized for the circuit length and pump load
- Waterproof marine electrical connectors
- Properly rated fuse and fuse holder
- Manual bilge-pump switch or compatible automatic control device
- Marine plywood mounting pad, fiberglass, and resin if required by the installation
- Wire stripper and crimping tool
- Circuit tester or multimeter
- Personal protective equipment
The Attwood Tsunami Mk2 bilge pump installation kit is designed for a manual Mk2 pump with a 3/4-inch hose outlet. The kit includes a through-hull connector, 5 feet of 3/4-inch inside-diameter hose, two clamps, 20 feet of 16-gauge wire, an on/off control switch, an inline fuse holder, and a 3-amp fuse.
Confirm that the kit’s hose diameter, wire size, fuse, switch, and through-hull fitting are appropriate for your particular pump and installation. A kit intended for the T500 should not automatically be used with a larger pump.
Step 1: Select the Installation Location
Position the pump in the lowest accessible part of the bilge where water naturally collects. On some sailboats, this may be near the centerline over the keel. The location should allow the pump to remove as much standing water as practical while remaining accessible for inspection, cleaning, testing, and cartridge removal.
Before drilling, confirm that:
- The pump sits level and securely on the mounting surface
- The pump inlet will not be obstructed
- The cartridge can be removed for maintenance
- The outlet can be aimed toward the discharge through-hull
- The hose can rise toward the outlet without unnecessary restrictions
- Wiring connections can remain above normal bilge-water levels
- The fasteners will not penetrate the hull, tank, wiring, plumbing, or another component
Do not mount a pump to the hull with fasteners that could penetrate the hull laminate. If a suitable mounting surface is not available, attach the pump to an approved mounting pad secured to the hull using an appropriate fiberglass and resin system.
Step 2: Plan the Discharge-Hose Route
The discharge hose should follow the shortest practical route from the pump to the through-hull fitting. Long hose runs, restrictive fittings, sharp bends, corrugated hose, and excessive elevation reduce the pump’s real-world output.
A pump’s advertised gallons-per-hour rating is normally measured under controlled conditions with little or no vertical lift. Actual output aboard a boat will be lower once discharge head, hose friction, bends, fittings, and electrical voltage loss are introduced.
Preventing an airlock
An airlock occurs when trapped air prevents the pump from moving water effectively. Route the discharge hose continuously upward toward the through-hull wherever possible. Avoid dips, loops, or low spots that can trap air or hold water.
Current Tsunami Mk2 pumps feature an X-Air impeller designed to help clear trapped air. Proper hose routing is still necessary and should not be replaced by reliance on the impeller design.
Preventing backflow and siphoning
The discharge opening must be positioned so outside water cannot flow or siphon back into the boat. Account for the boat’s loaded waterline and how it changes when the boat heels, turns, accelerates, or carries passengers and gear.
Install the discharge through-hull above the maximum waterline and use a vented loop when required by the boat’s design or the pump manufacturer’s instructions. Do not rely solely on a check valve to prevent flooding. A check valve also creates flow resistance and must be installed only when approved for the selected pump system.
Step 3: Install the Through-Hull Fitting
If the boat does not already have a suitable discharge through-hull, choose a location that remains safely above the waterline under all normal operating conditions. Check both sides of the proposed location before drilling.
- Confirm that the fitting is approved for use above the waterline and matches the hose diameter.
- Check for wiring, plumbing, structural members, and other hidden obstructions.
- Drill the opening according to the fitting manufacturer’s instructions.
- Seal exposed core material when working with a cored hull.
- Apply a marine sealant compatible with the hull and fitting materials.
- Secure the through-hull without overtightening or damaging the fitting.
- Allow the sealant to cure as directed before launching the boat.
A poorly positioned or improperly sealed through-hull can allow water into the boat. If you are uncertain about the location, hull construction, or sealing method, have the fitting installed by a qualified marine technician.
Step 4: Mount the Bilge Pump
Current Tsunami Mk2 pumps use external mounting feet and a universal mounting pattern. This allows the base to be installed without removing the basket and makes the cartridge accessible for future servicing.
- Set the pump in its planned location with the outlet aimed toward the discharge-hose route.
- Use the mounting feet as a template to mark the fastener locations.
- Remove the pump and check the space beneath every marked hole.
- Drill shallow pilot holes sized for the approved mounting fasteners.
- Place the pump over the holes and install the fasteners.
- Tighten the fasteners enough to secure the pump without cracking or distorting its base.
- Confirm that the cartridge release remains accessible.
CAUTION: Do not drill through the hull. Know the hull thickness and what is beneath the mounting surface before drilling any pilot hole.
Mounting a legacy Tsunami cartridge pump
Legacy Tsunami 4606, 4608, 4612, and 4613 Series pumps use a removable housing and base-strainer arrangement. On those models, the housing is released by depressing the locking tab and rotating the housing counterclockwise. The base is then used as a template for three mounting holes.
Reattach the legacy pump housing by inserting it into the base and rotating it clockwise until the locking tab engages. Consult the original instructions before disassembling or mounting a legacy pump.
Step 5: Connect the Discharge Hose
- Select smooth-bore, reinforced hose matching the pump outlet and through-hull fitting.
- Rotate or select the pump outlet that provides the most direct hose path.
- Cut the hose cleanly without leaving loose material inside it.
- Push the hose fully onto the pump outlet and through-hull barb.
- Secure each connection with marine-grade stainless steel hose clamps.
- Support the hose where necessary to prevent sagging, kinks, or chafing.
- Verify that the hose rises toward the discharge and does not create an air-trapping dip.
Do not reduce the hose diameter below the size specified for the pump. A smaller hose, a sharply bent hose, or a restrictive fitting can substantially reduce discharge capacity.
Inspect the entire hose run for contact with sharp edges, hot equipment, moving parts, or areas where cargo could crush it. Secure the hose without compressing or deforming it.
Step 6: Wire the Bilge Pump
Disconnect battery power before beginning any electrical work. All connections should be made above the highest anticipated bilge-water level using marine-grade wire and waterproof connectors.
The wire must be sized for the pump’s current draw and the complete round-trip circuit length. Excessive voltage drop reduces pump performance and may cause overheating or premature motor failure.
Manual-switch installation
A manually controlled Tsunami pump is generally connected through a dedicated bilge-pump switch:
- Connect the pump’s positive lead to the switched positive circuit.
- Connect the negative lead to the boat’s DC negative return.
- Install the specified fuse in the positive supply circuit.
- Label the helm switch clearly as the bilge-pump control.
- Confirm polarity before restoring power.
Attwood traditionally uses brown for the pump’s positive lead and black for its negative lead, but wire colors should always be confirmed using the instructions for the exact model. Reversed polarity can reduce performance or damage the pump.
Adding automatic operation
A manual Tsunami pump requires a compatible float switch or electronic water-sensing control to operate automatically. Wire the automatic control according to its own diagram and the pump manufacturer’s instructions.
An automatic bilge-pump circuit may require continuous power when the main battery switch is off. Do not modify or disconnect an existing automatic circuit without understanding the boat’s complete wiring system. The installation must include appropriate circuit protection and a way to test manual and automatic operation.
Fuse placement
Install the fuse in the positive conductor as close to the power source as required by the pump instructions and applicable marine electrical standards. Protect the wire throughout its route, secure it against movement, and keep it away from heat, sharp edges, fuel-system components, and areas where it may be submerged.
Failure to use the correct fuse or make waterproof connections can damage the pump and may affect warranty coverage.
Step 7: Test the Installation
Do not test a bilge pump by allowing it to run dry for an extended period. Add enough clean water to the bilge for the pump to operate normally.
- Inspect the bilge and verify that it contains no fuel, oil, or flammable liquid.
- Restore power to the circuit.
- Activate the manual switch and confirm that the pump starts.
- Verify that water exits through the intended discharge fitting.
- Inspect the pump, hose, clamps, and through-hull for leaks.
- Watch for hose collapse, excessive vibration, or restricted flow.
- Turn off the pump and check whether water drains back into the bilge.
- If an automatic control is installed, test it separately.
- Confirm that the pump shuts off correctly after the water level drops.
After the test, inspect the wiring and fuse holder for heat. A warm connection, intermittent operation, or unexpected voltage drop may indicate undersized wire, corrosion, poor crimping, a loose terminal, or another electrical problem.
Bilge Pump Maintenance
Even a correctly installed pump requires routine inspection. Debris, hair, leaves, fishing line, dirt, and other material can block the strainer or impeller. Hose clamps can loosen, electrical connections can corrode, and discharge hoses can kink or deteriorate.
Regular maintenance should include:
- Testing manual operation before leaving the dock
- Testing the automatic switch or sensor
- Cleaning the strainer and impeller area
- Inspecting the hose for cracks, kinks, and soft spots
- Checking clamps and through-hull fittings
- Inspecting wiring, connectors, and the fuse holder
- Removing oil, dirt, and loose debris from the bilge
- Confirming that the discharge opening remains unobstructed
- Listening for unusual motor noise
- Checking for unexplained increases in pump activity
A pump cycling more frequently than usual may be warning you about a leak. Find and correct the source of the water instead of relying on the pump to manage it continuously.
Troubleshooting an Attwood Tsunami Bilge Pump
The pump runs but does not discharge water
- Confirm that the water level is high enough to reach the pump inlet.
- Check the strainer and impeller for debris.
- Inspect the discharge hose for kinks, blockage, or collapse.
- Verify that the hose rises toward the through-hull without an air-trapping dip.
- Check the outlet and non-return valve, if fitted, for obstruction.
- Confirm that the electrical polarity is correct.
- Inspect the impeller for cracks, damage, or separation from the shaft.
- Make sure the discharge fitting is not submerged or blocked.
The pump does not run
- Check the fuse and replace it only with the specified rating.
- Verify battery voltage and the condition of the power source.
- Inspect the switch or automatic control.
- Check positive and negative connections for corrosion or looseness.
- Measure voltage at the pump while the circuit is switched on.
- Inspect the cartridge and impeller for blockage.
- Confirm that the pump’s current draw is not causing excessive voltage drop.
If a replacement fuse opens again, do not continue replacing it. Disconnect the circuit and find the underlying fault.
The pump runs but flow is lower than expected
- Check for low battery voltage or undersized wiring.
- Confirm that the pump is wired with the correct polarity.
- Shorten or straighten the hose route where practical.
- Remove unnecessary fittings and restrictions.
- Check the vertical distance between the pump and discharge.
- Clean the pump inlet, impeller, hose, and through-hull.
- Verify that the hose diameter matches the pump outlet.
Remember that advertised GPH is not the same as installed output. Flow decreases as discharge height and plumbing resistance increase.
Replacing or Cleaning the Pump Cartridge
One advantage of the Tsunami design is that the motor cartridge can be removed without replacing the complete installation. Disconnect power before releasing the cartridge.
- Remove standing water and debris from around the pump.
- Disconnect the power source.
- Release the cartridge using the mechanism provided for the model.
- Lift the cartridge out of the housing.
- Remove debris from the chamber, inlet, and impeller.
- Inspect the impeller, shaft, electrical leads, and sealing surfaces.
- Replace damaged components with parts specified for the exact pump.
- Reinstall the cartridge until its retaining mechanism locks securely.
- Restore power and test the pump with clean water.
For legacy Tsunami pumps, the original instructions specified matching the replacement cartridge to the housing series and color. The 500 Series used red, the 800 Series used blue, and the 1200 Series used gray. Do not use those legacy color references to select a cartridge for a current Mk2 pump. Match replacement parts by the current pump model and manufacturer part number.
When servicing a legacy cartridge O-ring, the original instructions called for vegetable oil and warned against petroleum-based lubricants, which can deteriorate the seal. For a current pump, use only the lubricant or service procedure approved in its instructions.
Choosing the Correct Bilge Pump
Bilge pump capacity is measured in gallons per hour, but the advertised rating alone does not determine whether a pump is appropriate for a particular boat. Consider the boat’s size, bilge layout, discharge height, hose length, electrical capacity, operating environment, and whether a secondary pump is needed.
Larger boats and boats with divided bilge spaces may require multiple pumps. A secondary pump mounted above the primary pump can provide additional capacity if the water rises beyond the primary system’s capability. Separate alarms and independent discharge routes may also be appropriate.
Browse our complete selection of boat bilge pumps to compare manual and automatic models, pumping capacities, voltages, and installation requirements.
Frequently Asked Questions About Attwood Tsunami Bilge Pumps
Is the Attwood Tsunami Mk2 an automatic bilge pump?
The Tsunami Mk2 is a manual-style bilge pump. It operates from a manual switch unless it is connected to a compatible float switch or electronic automatic control. Attwood Sahara Mk2 pumps are designed as integrated automatic models.
Where should an Attwood Tsunami bilge pump be mounted?
Mount the pump in the lowest accessible part of the bilge where water naturally collects. Keep the inlet unobstructed and leave enough access to inspect, clean, and remove the cartridge.
What fuse does an Attwood Tsunami Mk2 500 GPH pump use?
The current 12-volt Tsunami Mk2 T500 uses a 3-amp fuse. Fuse requirements differ for other capacities, voltages, and legacy models, so verify the rating on the pump label or current technical documentation.
What size hose does the Tsunami Mk2 500 use?
The current retail T500 includes outlet options for 3/4-inch and 1-inch hose. The correct hose must match the outlet installed on the pump and the discharge through-hull. The Attwood Tsunami Mk2 installation kit is intended for a 3/4-inch hose installation.
Why is my bilge pump running without moving water?
Common causes include an airlock, blocked inlet, damaged impeller, kinked discharge hose, obstructed check valve, incorrect polarity, or a discharge route with excessive height or restriction.
Can a bilge pump be connected directly to the battery?
An automatic bilge-pump circuit may be supplied independently of the main battery switch, but it still requires correctly sized wiring, proper circuit protection, and an approved control arrangement. Follow the pump instructions and applicable marine electrical standards.
Should a bilge pump discharge hose have a check valve?
A non-return valve may reduce drain-back, and Attwood recommends one for current Tsunami Mk2 installations. However, a valve also adds flow resistance and should never be the only protection against outside water entering through the discharge. Proper through-hull placement and an approved vented loop may still be necessary.
How often should I test my bilge pump?
Test manual and automatic operation regularly and before leaving the dock. Boats left in the water should also have the system inspected whenever possible after storms, maintenance, battery work, or an unexplained increase in pump activity.
Originally published July 16, 2009. Updated to include current Attwood Tsunami Mk2 features and installation considerations. This article provides general guidance and does not replace the instructions supplied with the pump or the services of a qualified marine technician.