When the owner of the boat notices that boat-engine It starts to splash water in different directions, often causing panic and concerns for the integrity of the engine. pump It's a problem, or a breakdown in the head of the unit, but the reality is often the fluid dynamics and design of the exhaust system, and understanding the physical processes inside the diewood can quickly distinguish between normal cooling and critical failure.
Water can be thrown out from under the water. anticavitational Or through special holes in the lower unit at different intensity and frequency, sometimes it's just a ripple of exhaust gases pushing out the residue of liquid, and in other cases, a sign of a blockage of the control hole or a failure. impellerIt is important to be able to distinguish between these conditions, so as not to drown out a serviceable engine in the middle of a reservoir or, conversely, to prevent fatal overheating of the power unit.
In this article, we will discuss in detail all possible scenarios, from absolutely normal modes of operation to symptoms of impending disaster. cooling-system by the nature of the jet and sound of the working engine, which will save time and money on maintenance.
Physics of the process: how the cooling system works
To understand why water emissions occur, you need to briefly consider the principle of operation. cooling-systemThe water is sucked in through the water intakes at the bottom of the lower unit and pumped upwards to the engine, and after the liquid removes heat from the cylinder shirt and the block head, it is mixed with the exhaust gas and released outwards.
The key here is that the exhaust in two-stroke and many four-stroke engines goes straight into the flow of outgoing water. The gases expand and create a ripple that pushes water out in jerks. It is this pulsation that often creates the effect of spitting or splashing, especially at low revs, when the pressure in the system is not yet high enough to form a flat, powerful jet.
In addition, the design of lower unit provides special channels to drain water that has got inside the casing or condensate. If the motor is idling, some of the water can flow out of the flow through the technological gaps, creating the illusion of a malfunction, although in fact it is a normal mode of operation. hydroelectric.
Remember that when idling, the jet from the control hole can be weak and intermittent – this is normal, since the centrifugal pump has not yet reached its estimated performance.
Normal work: when splashing isn't a problem
Many boat owners become unduly concerned about taking normal engine operating modes for failure, and there are situations where water splashing is a completely normal physical process, due to the design. exhaust.
First of all, you have to look at the mode of operation of the engine, because at low speeds, right after start or when trolling, the water often comes out in single portions rather than in a single stream. exhaust accumulate in the exhaust manifold and periodically push out the accumulated liquid with the characteristic sound of "snort".
It's also important to consider the position of the lower unit, because if the engine is raised too high or the boat is very different at the stern, water can flow into the exhaust pipe and splash back out when you start or change turns. transom-angle Or the position of the motor.
- 💧 Pulsating ejection at idling is a sign of the two-stroke cycle or the features of the release of the four-stroke.
- 💨 The release of steam along with water in cold weather is a normal condensation of hot gases.
- 🌊 Splashing water with a sharp addition of gas is an inertial effect in the exhaust tract.
If you see that from the control hole ("urinal") is a stable, albeit intermittent stream, and the temperature sensor does not show overheating, then with a probability of 99% of your boat-engine The only thing to worry about is if the jet disappears completely or gets too hot to the touch.
Symptoms of malfunction: when to sound the alarm
Despite the existence of normal regimes, there are clear indications that cooling-system Ignoring these symptoms can lead to severe overheating, jamming of the piston group and expensive overhauls.
The first alarm bell is that there's no water at all from the control hole when the engine is running at medium speeds, and if the engine is running and the urinal is dry, it means that the water is not circulating. pump-dipclogging of the water intake or depressurization of the suction tract.
The second major symptom is a chaotic splash of water from under the pads or lower unit compounds, accompanied by a whistle or hiss, which indicates that the system has created an excess pressure, and gases break out through weak spots, often indicating a breakdown of the gasket of the block head or a crack in the block. drain-manifold.
⚠️ Warning: If you notice that water is coming from the control hole with air bubbles or a whistling sound is heard, immediately turn off the engine. Continuing to work will cause instant overheating and deformation of parts.
Also, you should be alerted if the water from the urinal is very hot and the stream is weak, which may indicate that the pump is working, but the system capacity is reduced due to salt deposits or partial blockage of channels. hydraulic circuit.
The absence of a jet at medium speeds or the presence of air bubbles in the outgoing water are the main signals to immediately stop the engine.
Diagnosis of water pump and impeller
The most common cause of water discharge problems is wear or damage. pumpThis node is responsible for the circulation of fluid, and its failure paralyzes the entire cooling system, and the diagnosis begins with a visual inspection and checking for the presence of water flow.
The pump's winged wing is made of rubber or neoprene and is subject to wear and tear, and over time, the blades wear off, lose their elasticity and stop creating the necessary pressure, so that the water either stops being fed or is fed with a strong pulsation, which creates a spit effect.
To check the pump, you need to dismantle the bottom of the lower unit. When you look, pay attention to the integrity of the blades, the presence of cracks in the body and the condition of the O-rings. Often the problem is not the impeller itself, but the debris that gets inside - sand, algae or small stones that block the rotation. impeller.
Below is a table that helps classify the symptoms and probable causes of pump malfunction:
| A symptom. | Probable cause | Risk level | Action. |
|---|---|---|---|
| No jet on singles, there's on gas. | Wear of impeller, low pressure | Medium | Replacement of pumps in the nearest TO |
| The jet is completely missing. | Shaft break, jamming, debris | Critical | Immediate stop and repair |
| Bubble/vapour water | Gasping failure, crack. | High. | Defection of HBC and manifold |
| Weak pulsating jet | Canal clog, cuff wear | Medium | System washing, seal replacement |
When replacing the impeller, always change the base of the pump if there is a production on it. Using new parts on the worn body will lead to a rapid re-injuration of the pump. cooling-system.
☑️ Diagnostic pump
Clogs in the cooling system and lower unit
Another common reason why a outboard motor splashes or overheats is the common blockages, which contain sand, silt, algae and fine suspension that inevitably get inside the engine, and over time these deposits accumulate and narrow the passageway.
Special attention should be paid The urinal is very small in diameter, and even a small pebble or a lump of algae can completely block the water out, and then the pressure in the system increases, and the water starts to look for detours, breaking out through the glands or gaskets, creating a fountain effect.
Cleaning the system can be done independently using compressed air or thin wire (with caution). It is also effective to use special chemicals to remove scale and sediments that are poured into the cooling system according to the instructions for the treatment of the system. chemical composition.
- 🌿 Check your water intakes regularly for coiled algae.
- 🪨 After parking in shallow water, be sure to blow the system with air.
- 🧪 Use anticorrosion and anti-scaling additives for prevention.
If the pattern of the launching has not changed after cleaning the urinal, the problem may lie deeper in the cylinder block cooling shirt, requiring more serious pressure washing of the entire system or even partial disassembly of the engine to remove the fossilized deposits.
How do you properly flush the system?
To flush efficiently, use a special tap nozzle ("ears"). Connect the hose, start the engine at idle speeds and let it work for 5-10 minutes. The water should go clean. Do not allow the engine to work without water for a second!>
Problems with thermostat and gaskets
In four-stroke outboard motors, as well as in some powerful two-strokes, installed thermostatThis valve regulates the flow of water, directing it either in a small circle (for quick warming) or in a large one (through a radiator or directly into the discharge).
If the thermostat jams in the closed position, the water can't escape, the pressure rises, and the engine starts to spit through safety valves or weak connections. If the valve does not hold, the motor warms up for a long time, and at low revs, the water can flow out of the water by gravity, creating a weak, dripping jet.
The gaskets are also worth mentioning: the cylinder head (CBC) and exhaust manifold are constantly exposed to high temperatures and pressures, and when they break through, exhaust gases break into the water jacket, causing a sharp increase in pressure, boiling water in local areas, and powerful emissions of vapor and water mixture through the control hole.
⚠️ Attention: Sign of failure of the gasket gasket HBC - whitish smoke from the exhaust and emulsion (water with oil) on the probe.
The thermostat is diagnosed by heating it in a water tank, opening at the temperature specified in the specification (usually around 50-60°C) and opening completely at the operating temperature, and if the valve is not moving or moving in jerks, it must be replaced.
Replacement of gaskets and thermostat requires removing the top of the lower unit and the head of the block. Use only original gaskets or quality analogues, as use of sealant instead of gaskets in the cooling system of the outboard motor is unacceptable due to the risk of separation of sealant particles and clogging of thin channels.
Prevention and proper care of the system
That the question of why the outboard motor splashes didn't bother you in the middle of the season, you need to pay attention to prevention. boat-engine and its cooling system.
First of all, after each operation in salt water, the motor must be washed with fresh water, the salt crystallizes in the channels, narrowing them and causing corrosion of metal parts, and it is better to wash with special "ears" or a wash tank, allowing water to flow through the system.
It is also recommended to change the water pump annually before the start of the season, the cost of a remix is incomparable with repairing an overheated engine, and in winter storage, it is advisable to preserve the system by pouring corrosion-resistant compound or freeze-free liquid inside to prevent rust from forming during downtime.
By following these simple rules, you will ensure a stable job. hydroelectric And avoid the unpleasant surprises on the water, and remember that water is your motor's friend, but only if it circulates properly and freely.
Frequently Asked Questions (FAQ)
Why does the engine only squirt water when idling?
When idling, the pressure from the water pump is minimal. The exhaust gases push the water out in jerks, creating a ripple effect. If you add the gas, the jet becomes flat and powerful, then that's normal engine operation.
What to do if water stops flowing from the control hole?
Turn off the engine immediately. Movement without cooling will cause the pistons to jam in a few minutes. Check the water intakes for debris, inspect the impeller pump and make sure the urinal is not full.
Can you use a motor if it is spitting a little water?
If the main hole is stable, the temperature is normal and there are no signs of gasket failure (bubbles, emulsion), then short-term operation is possible, however, at the earliest opportunity, a diagnosis should be made, as this can be a harbinger of serious failure.
How often should I change the water pump?
The recommended replacement interval is every 2-3 seasons or 300 hours, but when used in dirty water or sand, it is worth replacing annually, since the abrasive wear of rubber is faster.
Why is the engine warmed, even though the water is coming out of the hole?
This could indicate clogging of cooling channels inside the engine (scale), a malfunctioning thermostat or air entering the system. It is also possible that the pump is worn out and does not create enough pressure to efficiently remove heat despite the presence of flow.