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A boating or fishing trip with your family and friends is always a great idea. But if your outboard water pump develops some issues, it can through a wrench in your plans.
Imagine what it would be like to get stuck on the water. If not rectified, these issues can even affect the boat’s engine and lead to more problems.
One of the best ways to prevent that from happening is to get it serviced at the beginning of each season. Even so, it’s best to stay prepared and keep a pump maintenance kit with you in case any emergency maintenance is needed.
If you aren’t sure about picking the right repair kit, not to worry. In this article, we will take a look in detail at the repairing of water pumps and repair kits.
To start with, let’s take a quick look at water pumps and their features.
I believe the Quicksilver 96148Q8 Water Pump Repair Kit is the best bang for your buck.
What Is a Water Pump?
Before we talk about the water pump, let’s take a look at the main purpose it serves in the boat.
Most boats come with a typical outboard motor that includes the engine, gearbox, and propeller. It’s a simple but compact system that also provides some steering control to the boat.
As the gas is burned in the motor, the temperatures around the inner components rise sharply. The heat buildup is very high around the piston rods and the cylinders as they move. Unless this heat is carried away, it can cause severe damage to the engine. It can even melt or distort the engine parts.
Needless to say, such damage can’t be repaired.
To cool the engine, a cooling system is used. It uses water as the cooling agent. This brings us to the water pump which makes the water flow into the engine and carry away the heat. The pump is usually located below the water level to make the suction process easier.
Now, some boats use the raw water cooling system. In this system, the water that the boat is floating in is pumped directly into the engine casing through a seacock by the pump. The water absorbs the heat and is released through an exhaust port.
This is a direct and least expensive method. The disadvantage of the system is, seawater is corrosive. It can wear away the metal parts of the engine and decrease its lifespan. Saltwater also causes scaling inside the engine jacket that can affect heat transfer. This may cause the engine to overheat.
That’s why most newer engines use indirect cooling or some form of a heat exchanger. Here, a small tank containing fresh water and coolant sits on the top of the engine. This is usually a 50/50 mixture. In cold weather, the coolant also acts as an antifreeze.
This fluid is circulated through the engine and then through a heat exchanger. The fluid absorbs heat from the engine and releases the heat to the raw water in the heat exchanger.
The cooler raw water absorbs the heat and is released out through the exhaust. The water pump controls the flow of raw water into the heat exchanger.
Note, some amount of scaling from the raw water also happens in the heat exchanger. But this can be removed by acid treatment. Even if the heat exchanger needs replacement, it’s less expensive than replacing the engine.
There are various other parts in the cooling system like the seacock, sea strainer, multiple hoses and clamps, belts, and the water pump impeller.
The seacock comes with a shut-off handle that allows you to stop the entry of raw water if needed. The strainer is a filter that removes particles, sand, and other organic material from the raw water. The hoses, clamps, and belts create a steady pathway for the water to flow in.
In the heart of the cooling system, lies the water pump which is driven by a belt that draws power from the engine. In most cases, a centrifugal pump is used. The most important part of the pump that drives the water is the rubber impeller that lies inside the pump casing.
What Is an Impeller?
The impeller is connected to the driveshaft in the pump. It’s a star-shaped component with paddles or fins that sweep the water through the pump. The impeller is placed off-center inside the pump housing to compress the water.
As the water enters the pump from one end the rotating impeller blades add to the pressure and force it out. The pressurized water exits from the pump outlet.
Remember, while the impeller is one of the smallest components in the pump, it’s the most common cause of engine overheating. And more than often, the impeller gets damaged from lack of use rather than overuse.
A damaged impeller can not only reduce pump efficiency but can damage the engine as well. Broken pieces from the impeller can block the engine in a direct raw water-cooling system. It can also damage the interiors of a heat exchanger.
Once the water flow in the cooling system is restricted, your joyride over water can swiftly turn from a fun event into a nightmare.
There are quite a few reasons that can cause an impeller to malfunction. Here’s a look at some of the major ones.
- Dirty or silty water contains small particles that can damage the impeller and clog the cooling system. This can happen when silt is kicked up to the surface by other boats or due to water plants. It’s important to check that the pump strainer is in good condition.
- If the boat is running too shallow, abrasive sediment can get sucked into the pump and overheat the impellers.
- When left dry and unused for long periods, the rubber components in the impeller can deteriorate. This also makes the impeller blades brittle and they can break apart under pressure. If your boat has been sitting idle for more than a year, it’s best to replace the impeller before heading out.
- When a boat engine is made to run dry, the generated heat can easily damage the impellers. Some research states that running an engine out of water for even 20 to 30 seconds can cook the pump impellers. In fact, running a pump dry can lead to total pump failure.
How To Get Most Out of the Pump Impeller?
There are a few simple steps you can take to prolong the life of the pump impeller. Let’s take a look.
- It’s best to remove the impeller from the pump housing if you aren’t planning to use the boat for a long period. Keeping the impeller inside the pump can deform the blades.
- Periodic inspection of the impeller for any defect is a must. Even if it appears undamaged, replace the impeller as per the guidelines of the OEM. That way you will get more reliable performance.
- While replacing the impeller, use waterproof grease or any other lubricant as mentioned by the pump manufacturer. This will prolong the impeller’s life and it will be easily removable when needed.
How to Know if a Water Pump Needs to be Replaced?
There are four main signs that indicate that a water pump needs replacement.
One of the common signs of a malfunctioning water pump is the overheating of the engine.
At times, water may not come out from the cooling water outlet line due to internal blockages. This will require a closer inspection of the entire cooling system and making the necessary repairs. There can also be water leakage due to a crack in the pump housing or in a hose.
That said, an overheating engine may not be related to a damaged impeller at all times. At times, the hoses or tubes carrying water can get blocked by debris. Also, make sure that the engine oil is filled up to the proper level and there are no faulty spark plugs.
Reduced Outboard Performance
Is your outboard failing to throttle up and getting bogged down? This can be due to a malfunctioning water pump.
If the water supply from the pump isn’t consistent, the engine will not be cooled at a uniform rate. This will make the engine reduce performance during high RPMs due to the extra heat in the system. A continued operation like this will lead to the complete failure of the pump and engine damage.
Take note: this condition can be difficult to point out, especially during the winter months. The engine may cool down due to the low ambient temperature and operate normally. But the pump will continue malfunctioning and the problem will reappear in summer.
Beyond that, there are some other causes that can affect the engine’s performance. These include a tangled propeller, clogged fuel filter, poor gas quality, and damaged fuel pump or fuel hose.
We have already discussed the main causes of impeller damage. The impeller should be inspected for any damage at least once annually. If you are a DIY-er, check for missing or broken blades, cracks on the blade surface, blade deformation blades, and damaged blade tips.
With continued performance, the impeller vanes can lose flexibility. This may cause them to bend towards one side. In most cases, some damage can be noticed at the impeller vane roots after around 300 hours of use.
This is one reason that you need to carry complete water pump impeller replacement kits in your boat. The good news is that impellers aren’t expensive and are not difficult to replace.
Whining or Grinding Noises
In most cases, whining or grinding noise can be due to a loose pump drive belt or some issues with the drive pulley. Pulleys may get damaged due to rust and loosening of bolts. This may cause some flex in the pulley during spinning, resulting in the noise. Wear of the drive belt can also result in a whining noise.
Worn-out bearings in the pump can also cause a clicking or a rattling noise. Also, a broken piece of the impeller shaft can cause a rattling noise.
What Is a Water Pump Kit?
A water pump repair kit comes with all the parts that are necessary to fix a water pump issue. Some kits are specially designed for specific pumps from a particular brand. Since the impeller is one of the most commonly replaced components in the pump, a pump kit comes with the impeller. It can also contain other components like gaskets, plates, keys, guides, and thrusts.
How to Choose a Water Pump Kit?
When choosing a water pump kit, the following points are to be kept in mind.
- Make sure that the components in the kit have the right specifications to match your pump. Check the nomenclature of the outboard models for which the kit is designed.
- It’s best to choose a kit from the pump manufacturer. Otherwise, make sure you choose from a reliable brand. Check the reviews regarding the kit before buying. Take help from experienced technicians before choosing the kit.
- The components should be made from quality materials to ensure the best performance. Ideally, they should be tested for durability, dimensional precision, and leaks.
- A cheap kit may not be the best option. It’s good to maintain the right balance between price and quality while choosing.
How to Replace the Impeller in an Outboard Water Pump?
Basically, outboard water pumps come with a simple design and are easy to replace. Here’s a step-by-step process for replacing the impeller in a water pump.
- Start by shifting the motor into reverse gear. Then the mounting bolts and nuts to disconnect the shift rod. Don’t miss the bolts located under the trim tab.
- The process of disconnecting the shift rod can vary depending on the design. Check out the product-specific instructions for details.
- Next, take out the bolts on the water pump housing. Remove the housing, the impeller, and the gaskets from the gear case.
- Install the new pump plates, gaskets, and impeller. Lubricate the impeller seat, the splines of the driveshaft, and the keyway.
- Line up the impeller with the impeller key. The impeller is usually set in place by twisting it slightly clockwise and pushing it in.
- Now, place the pump housing in position. For standard rotation pumps, you need to turn the driveshaft clockwise while replacing the housing. Tighten the housing bolts and ensure that the gaskets are sealed.
- Place a new water tube seal on the pump entry point. While installing the lower unit, line up the driveshaft, water tube, and shift rod properly.
- Lubricate and tighten the bolts that connect the lower unit.
- Lastly, run the engine and ensure that the cooling system is functioning properly.
Best Outboard Water Pump Kits
Time to take a look at the top five Mercury outboard water pump kits in the market.
All repair kits from Quicksilver are designed to match original equipment from Mercury Marine and ensure high quality and performance. This kit is for 65 hp (4-cylinder) and V-6 outboards. It comes with a pump housing assembly, gaskets, plates, faceplates, impeller, key, and water tube guide sleeve.
Quicksilver mentions that each item has been rigorously tested to offer the best performance. The fit is perfect and users appreciated the overall quality of the items. While this kit comes with a higher price tag, you can depend on the quality.
- Superior quality from Quicksilver
- Includes all necessary components
- The fit is great
- A relatively high price tag
- Not for all Mercury models
This is another high-quality repair kit for the Mercury Mercruiser Alpha One. As expected, you get the whole range of parts necessary for impeller replacement. It also includes a seal and key.
The kit comes with a nitrile rubber impeller that has a brass hub. The material is suited for high flows and is resistant to corrosion. The rubber also offers good wear resistance. The overall fit and finish are top-notch.
Considering the price to performance factor, this is one of the best options in this category.
- A good quality repair kit
- Durable rubber for the impeller
- Offers great value
- No instructions for first-timers
This is a kit for the Mercruiser Alpha One and offers all the components you need for replacing the impeller. It contains gaskets, plates, and also includes the top segment of the pump housing. Most users found the quality of the impeller and the gaskets to be top-notch. The fit and finish are good too.
At this price, it’s a value for money choice.
- Good quality spares
- It’s inexpensive
- The pump housing is not of the best quality
This repair kit is for Mercruiser Alpha One Generation I sterndrives. It comes with all the necessary parts including the gasket and the housing. Users mentioned that the fit was as good as the original product. Also, there are extra gaskets included in the product
The materials for each component are carefully chosen to provide corrosion and abrasion resistance. The impeller is made from neoprene rubber and comes with a brass sleeve that adds to the overall durability and performance.
The kit is priced slightly higher. But considering the quality, I’m not complaining.
- High-quality materials used
- Includes all necessary components
- Offers good value
- A higher price tag
This impeller replacement kit is for Mercruiser I, R, MR and Alpha One drives and a whole range of Mercury 2-stroke outboards. It comes with a full collection of items required for an impeller replacement including gaskets of various sizes. The additional gaskets will fit the different engine variations.
The quality is well-maintained and customers appreciated the overall fit and finish. On the whole, another repair kit that offers excellent value.
- Good quality materials
- Includes all necessary components
- Offers good value
- Doesn’t fit the Alpha-1 GEN-II model
This is a comprehensive impeller repair kit for 4-stroke Mercury outboards ranging between 30 HP and 25 HP. The kit comes with an impeller, both upper and lower housings, faceplate, gaskets, and seals.
As expected from Quicksilver, the quality of the materials, as well as the finish, is top-grade. As per the users, the dimensional precision of the parts was good.
On the downside, this is a costly kit. So, budget buyers need to look elsewhere.
- A top-quality repair kit
- Comes with a complete housing
- Good quality impeller
- It’s pricey.
Frequently Asked Questions
Answer: Usually, Mercury impellers should be changed after every 3 years. In case the impeller is damaged and the cooling system isn’t functioning properly, you may need to change it earlier.
Answer: Yes, it can. One major reason is due to corrosion from various particles in the water like sand. An impeller left dry and unused for a few years can also go bad.
Answer: The pump impeller in a boat is located inside the water pump. You need to open the pump housing to access it.
Answer: It’s not a difficult task and a necessary DIY activity for every boater. Usually, changing an impeller takes around 20 to 30 minutes.
Answer: Once you take out the impeller, you can use pliers or some wire to take out any debris that’s blocking it. Then flush it with clean water before reinstalling.
There you have it. I have listed the best Mercury outboard water pump kits from the current market.
For us, the Quicksilver 96148Q8 water pump repair kit was the top pick in this category. What I like is the excellent quality control by Quicksilver that ensures that each component is made from top-grade materials and fits precisely. That gives you additional peace of mind after replacing an impeller.
Now, the choice is yours.
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