Work. boat-engine Without an efficient cooling system, it's impossible in principle, because overheating leads to a jamming of the piston group in a matter of minutes. water-cooled pumpThis is a water system that allows constant circulation of water from the reservoir through the engine shirt, and water technology owners often face the need to maintain this particular unit, as it is subject to wear and tear of rubber parts and abrasive effects of sand.
In this article, we will analyze in detail Construction of the water pump, consider the typical symptoms of failure and step by step describe the replacement process. impeller Understanding the pump will allow you to avoid expensive overhaul of the engine and provide confidence in the reliability of your engine. outboard During long-distance waterways.
Even short-term operation of the engine "dry" or with impaired circulation can be fatal for the engine. Carburetor and injection enginesTherefore, regular checks of the "control jet" should be a mandatory ritual before each navigation and during operation.
The principle of operation of the cooling system of the outboard motor
The water cooling system in outboard motors is built on a closed principle of pumping off-shore water. impeller Or an impeller made of flexible rubber, and when you rotate the shaft in a certain direction, the petals of the impellers deform, creating zones of thinning and pressure, which causes the water to rise upwards. waterway up to the thermostat and cylinder head.
⚠️ Note: It is strictly forbidden to start the motor out of water or without pre-submitted water into the water intake, since dry friction instantly destroys the rubber impeller.
Water passing through water-shirt The cylinder block, which takes the excess heat, then either ejects it through the control hole or passes through the thermostat to maintain the operating temperature, depends on the state of the rubber pump elements and the purity of the process. waterwayAny clogging or wear of parts leads to a decrease in the pump performance.
It's important to note that the direction of rotation of the pump shaft is strictly regulated by the manufacturer, so if you mix up the direction of rotation when you assemble it or if you install the impeller incorrectly, water-circulation It's either not going to start at all or it's going to be very inefficient. In some motors, especially in China, the direction of rotation may be different from Japanese or American models.
Typical signs of water pump malfunction
There are a number of indirect and direct signs that can be used to identify cooling problems, and the first and most obvious symptom is the absence or weak control jet from a special hole in lower unit, but you shouldn't rely on visual water control alone, because the hole can become overgrown with algae or silt.
More alarming signals requiring immediate engine stop are:
- 🔥 The appearance of a pair from under the casing of the motor or characteristic hissing.
- 📉 A sharp drop in traction and power caused by thermal expansion of parts and a drop in compression.
- 👃 The smell of burnt rubber or burnt oil, indicating overheating.
- 🔊 Change in the sound of the engine, the appearance of detonation (sound knock).
It is also worth paying attention to the state of heaterIf it is designed by your design. boat-engineModern ECU systems can reduce engine speeds by themselves when critical temperatures are fixed, going into emergency mode, and ignoring these signals leads to liners turning and bullying in cylinders.
Diagnostics and preparation for pump repair
Before you start disassembling a node, you need to make a competent diagnosis. Often the problem lies not in the pump itself, but in the clogged. waterway Visual examination of a lower unit for cracks and dents can reveal the locations of the air suction that disrupts the water pump.
You'll need a standard toolkit and some specific materials to do the work. Be sure to prepare a sealant to seal the joints, as reuse of old pads is not allowed. WD-40 or similar penetrating lubricant to facilitate the dismantling of boiling bolts.
The preparation process includes the following stages:
- 🛠️ Drain the residue of fuel and oil from lower unit (if necessary).
- 🧼 Careful washing of the external part of the motor from salt and dirt.
- 🔧 Fixing the motor in a vertical position at a comfortable height.
- 📸 Photographing the joints of hoses before they are disconnected.
⚠️ Warning: When removing lower unit, be careful with gear shift thrusts and a rod-rod so as not to damage their geometry and settings.
Step-by-step instructions for replacing the impeller
Replacement pump-dip In most cases, the engine's lower unit (leg) must be dismantled to access the pump, a time-consuming process, but it provides better access to the nodes and allows for a complete system audit.
Once the motor leg is removed and the water pipes are disconnected, you will have access to the pump body, which is usually attached with several bolts to the cylinder block. When you remove the lid, you will see the impeller itself, which is worn on the shaft. Often you need to remove the locking ring or veneer to free the shaft to remove the old part.
☑️ Checklist for pump replacement
When installing a new part, it is critically important to lubricate the petals of the impeller soap-solution This will prevent damage to the rubber from being initially run dry until the water fills the system, and it will also be necessary to strictly observe the direction of rotation indicated by the arrow on the body or in the manual.
Nuances of impeller lubrication
The use of solidol or litol to lubricate the impeller is not recommended, as these lubricants can not dissolve well in water and contaminate the system. It is best to use ordinary soap diluted in water, or specialized water-soluble lubricant.
Selection of spare parts: original or analogue?
Parts market for boat-engine Owners often face a choice: buy an expensive original part from the company. Yamaha, Mercury or TohatsuOr use more affordable rubber, which can be much inferior to the original in cheap copies, leading to a quick failure.
Original parts ensure compliance with all sizes and temperature regimes. However, quality aftermarket manufacturers such as Sierra, Mallory or OMP often offer products that are not inferior in resource, but at a more attractive price, the main thing is to avoid frankly cheap "no-name" kits.
Comparison of specifications of different parts options:
| Type of spare part | Resource (motowatch) | Price. | Quality assurance |
|---|---|---|---|
| Original (OEM) | 1000+ | High. | Maximum |
| Brand-like | 800-1000 | Medium | High. |
| Budgetary analogue | 200-400 | Low. | Medium/Low |
| Chinese "no-name" | 50-100 | Minimum | Missing. |
When choosing a kit for repair, pay attention to the presence in the set not only impellers, but also a new one. shell-layingThe sleeve of the pump, the ossification rings, and sometimes the base of the pump, and the complete replacement of all the rubber elements will ensure that the unit will operate for a long and reliable period of time.
Maintenance and prevention of cooling system
And boat-motor It's been in the long run, and it's a very regular preventive measure, especially in contaminated water, and sand, silt and algae are the main enemies of the water pump, causing abrasive wear and clogging.
After each operation in salt water, the motor must be washed with fresh water, and for this purpose, there are special devices ("ears") or wash tanks, which allows you to remove salt, which crystallizes and can damage. rubber-seal and metal parts.
When preserving the engine for the winter, be sure to treat the internal cavities of the cooling system with an anti-corrosion composition or preserve an ice-free liquid to prevent rubber from cracking from dryness.
The frequency of impeller replacement depends on the intensity of use. pump-box Every 2-3 seasons or 300 hours of motorized work, but if you are often in shallow water or working in sand water, this interval should be reduced by half.
Frequent mistakes in water pump repair
Even experienced mechanics sometimes make mistakes that can cost the engine its life, and one of the most common is the use of an inappropriate sealant, and some formulations may contain aggressive rubber-breaking components or may not withstand extreme temperatures, leading to leakage.
Another mistake is not tightening the bolts of the pump body sufficiently or breaking the tightening sequence, which causes the body to skew and the impeller to fit unevenly, causing vibration and rapid wear. Always use the dynamometer key and follow the manufacturer's specifications.
⚠️ Warning: Never use silicone sealants that are not intended to come into contact with gasoline and oil to seal the cooling system, as they can break down and clog up thin cooling channels.
Also often ignored is the state of the pump shaft itself, and if there is a production or corrosion on the shaft at the impeller landing site, the new part will quickly fail, in which case the shaft itself needs to be replaced or the seat restored.
High-quality pump installation using original or proven analogues of spare parts and the correct sealing materials is the key to the absence of engine overheating at the most inopportune moment.
FAQ: Frequently asked questions
How often should I change the pump?
The recommended frequency of replacement is every 2-3 years or every 300 hours, however, when operating in sandy or silted water bodies, the interval should be reduced to 100-150 hours.
Can I lubricate the impeller with solidol?
Solidol, litol or graphite lubricant are not recommended, they are poorly soluble in water and can contaminate the system, and it is best to use a soap solution or a special water-soluble lubricant.
Why is there no jet from the control hole, but the engine is not warm?
It's probably a salt or algae clogged in the control hole itself, and it could be a crack in the lower unit that drains water, or a malfunctioning thermostat that directs the entire flow around the hole.
Does the direction of rotation of the screw affect the pump?
Yes, the direction of the pump shaft is strictly defined by design. When installing the propeller opposite rotation (left instead of right), you need to make sure that the engine design provides for the pump to work in this direction, or to switch the pump in a new direction if possible.
Which sealant is best used for the pump body?
Special marine sealants (such as Permatex Marine) that are resistant to water, oil and gasoline must be used, and a conventional car sealant can fail to withstand operating conditions and dissolve.