Breakdown of the bottom of the outboard motor is always an unpleasant surprise, capable of ruining a fishing or walk. Mercury You have to be prepared for the fact that even a reliable American assembly will require intervention over time. Mercury outboard motor Reductor It is a complex mechanism operating in an aggressive environment where water, sand and impact loads do their job. Ignoring the first signs of malfunction, such as extraneous noise or loss of traction, can lead to expensive overhauls or complete replacement of the unit.
Many boat owners mistakenly believe that maintenance of the lower gear is only a regular change of oil, but this is not enough for the long life of the unit. Internal components, including gears and bearings, are subject to wear and seals lose elasticity under the influence of temperature changes. gear-breaker Not only does it help to restore the boat's performance, but it also prevents a sudden failure away from shore, and in this article we will discuss in detail the stages of diagnostics, disassembly and assembly of the mechanism, so that you can perform the work as efficiently as possible.
It is worth noting that the design of the lower gears Mercury It has unique features that distinguish it from other manufacturers, such as the gearshift system and propeller shaft sealing scheme, which can vary depending on the year of production and engine model. Accurate diagnosis Before starting work, it will save time and avoid buying unnecessary parts, and below we will discuss the main symptoms of malfunctions and methods for eliminating them.
Diagnosis of gearbox malfunctions
The first step to a successful recovery is to identify the problem accurately, and often owners start disassembling without a clear understanding of what exactly went wrong, which leads to unnecessary costs. downshift There's an increased noise level, body vibration, and an emulsion in the oil, and an emulsion that looks like mayonnaise or condensed milk indicates that water has entered the body through the damaged omentation.
Visual inspection is also critical in diagnostics, and you need to look carefully at the body for cracks, dents and corrosion, and you need to pay special attention to the shafts and the junctions of the halves of the crankcase, and if you notice oil leakage or water leakage, it's a direct signal to replace it. sealing-ring Sometimes the problem is not the gearbox itself, but the damage to the propeller, which creates imbalance and vibration.
⚠️ Attention: The operation of the engine with emulsified oil in the gearbox is strictly prohibited. The water in the oil leads to rapid destruction of bearings and corrosion of gears, which may require a complete replacement of the unit.
A deeper diagnosis may require removing the gearbox from the lower unit, which will allow you to check the shafts and the condition of the gear teeth. If you scroll the shaft with your hand, you feel jamming or you hear a crunch, then the bearings or gears need to be replaced. switcherAs its wear often leads to problems with the inclusion of gears.
Tools and training required
You can't have a good repair without the right tools. Mercury You'll need not only a standard set of wrenches, but also specialized tools. If you don't have the right tool, you can damage the threaded joints or deform parts when you disassemble. Before you start, make sure you have access to a workbench and a clean workplace.
The main tool list includes a dynamometer key, a set of heads, bearing removers and gland pressing mandrels, special probes for measuring gaps and a clock-type indicator for checking the beating of the shafts, be sure to prepare containers for draining old oil and a solvent for washing parts.
- 🛠️ A set of end heads and a rattle for unscrewing fasteners.
- 🔧 Special detachment for removing the propeller and the locking nut.
- 📏 Footprints and indicator for accurate measurement of gaps and backlashes.
- 🧴 Sea sealant for marine engines and lubricant for bearings.
An important step in preparation is to clean the outer surface of the gearbox from dirt, algae and fish scales, which will prevent abrasive particles from entering the mechanism during disassembly, and it is recommended to also photograph the initial position of the rods and control levers, so that during assembly there are no problems with adjusting the gearshift.
Lower gear disassembly process
Disassembly of gearbox Mercury The first thing you do is remove the propeller by removing the locking washer and the nut, and then you disconnect the gear shift traction and you unscrew the bolts that connect the gearbox to the lower unit, and when you remove the bottom, you don't have to damage the pad, and you make sure that the switching rod comes out of the engagement correctly.
Once the gearbox is removed from the engine, it is then disassembled into components, first the propeller shaft is removed along with the reversing gear, which may require heating the body or using a removable if the parts are boiling, then the vertical shaft is removed from the forward gears, all the parts must be thoroughly washed in solvent and laid out in assembly order.
☑️ Preparation for disassembly
Special attention should be paid to the condition of the gaskets and seals. Often it happens that metal gaskets can be reused if they are not damaged, but rubber seals are better replaced immediately. When removing the shafts, it is important not to scratch the bearing seats, as this can lead to leakage in the future.
Defection and replacement of worn parts
After complete disassembly and cleaning, every part is thoroughly defective; the gears are checked for chipping, metal staining and tooth wear; bearings must not have backlash or noise when rotating; if corrosion or pitting is visible on the surface of the balls or rollers, the bearing must be replaced.
The shafts are checked for beating and wear of the seats under the glands. Even a slight wear of the shaft at the contact point with the cuff can cause leakage. In such cases, the shaft must be replaced or restored by spraying and draining. switch-off and cam clutch, as their wear leads to spontaneous flight of the transmission.
| Component | Sign of wear and tear. | Action. |
|---|---|---|
| Bearings | Luft, noise, corrosion | Replacement |
| Salmon | Hardness, cracks. | Replacement |
| Scooterney. | Chip, tooth wear | Couple replacement |
| Gasting | Breaking, loss of elasticity | Replacement |
When defective, the condition of the gearbox body is also assessed. Cracks or severe corrosion of aluminum can make further operation dangerous. In some cases, cracks can be brewed with argon welding, but this requires a high skill of the master. If the case has through corrosion holes, the gearbox is easier to replace with a new or rebuilt one.
How to check the gears for hidden defects?
To detect microcracks in the gears, you can use magnetic flaw detection or look closely at the teeth under the magnifying glass in bright light, and any change in metal color or microscopic cracks at the base of the tooth indicate the need for replacement.
Gaps assembly and adjustment
Constructing the gearbox Mercury All bearings must be pressed to the shafts to the end using special mandrels. Before installing the boulders, it is recommended to lubricate their working edges with a consistent lubricant to prevent damage during the initial start. The gaskets are lubricated with sealant on both sides to ensure reliable sealing.
A critical step is to adjust the gaps in gear engagement and the pre-stretching of the bearings, and this is done by selecting adjusting washers of different thicknesses. Carburetor gap The backlash must meet the manufacturer's specifications for the particular model, too much gap will lead to noise and impact loads, and too little will lead to overheating and bullying.
⚠️ Warning: Incorrect adjustment of the gap gears is the main reason for the rapid failure of the repaired gearbox. Use only original washers and accurate measuring instruments.
To measure the gap, you use a clock-type indicator attached to the gearbox body, and you turn the shaft both ways, and you get a difference, and if you don't get a value, you get a new adjustment washer, and it can take a few tries, but it's worth it.
When assembling the gearbox, always use new lock nuts and splints. Reusing old fasteners can cause them to be cut under load and the propeller to lose.
Testing and maintenance after repair
After assembly and installation of the gearbox on the motor, you need to conduct testing, first check the ease of shifting gears on the shut-down engine, then start the engine on the shore (required with water supply!) and check the operation at idle speeds, the absence of extraneous noise and vibrations indicates the correctness of the work performed.
The first step to the water should be careful. You should not immediately give full gas, it is better to check the gearbox in different modes. After a few hours of operation, it is recommended to check the oil level and its condition again, if the oil remains transparent and its level has not changed, then the leakage is restored successfully.
Regular maintenance will prolong the life of the repaired unit. Change the oil in the gearbox at least once a season or every 100 motor hours. When storing the boat in winter, it is better to remove the gearbox or at least turn the shaft regularly so that the lubrication is distributed to the bearings.
The quality of the used parts and the accuracy of the gap adjustment determine 90% of the success of the repair of the Mercury gearbox.
Frequently Asked Questions (FAQ)
How often should I change the oil in the Mercury gearbox?
The gearbox oil should be changed at least once a year before navigation, or every 100 hours, and if you notice an emulsion, you should replace it immediately after eliminating the cause of the water intake.
Can I use conventional transmission oil?
No, for boat gearboxes. Mercury You need to use special oils labeled API GL-5 and add additives against foaming and corrosion of non-ferrous metals. Conventional automotive oil can lead to the destruction of bronze gears.
Why does the gearbox hum after repair?
The buzzing can be caused by improper adjustment of the gap of the gears, the use of poor-quality bearings or insufficient oil levels, and the production of new parts may also be defective.
Do I need to smear the sliver of the propeller?
Yes, the shaft slits and screw hubs must be lubricated with a special lubricant that does not contain molybdenum disulfide to prevent stiffening and corrosion, which will make it easier to remove the screw in the future.