An article from Marine Technician Today Magazine outlining the process of a tune-up on your boat engine. ... read more -- By Bill Brannis (Marine Technician Today Magazine; Summer 2013)
What exactly is a tune-up ? By definition a tune-up is a series of lubrications, tests, and adjustments that the manufacturer requires at specified intervals to keep the engine in peak operating condition.
A quality shop will perform various checks and procedures to keep their customers happy and remaining loyal to them. No technician or shop owner wants to hear about a customer stranded on the water like the couple shown in Figure #1.
Most outboards require service every 100 hours or once a year, whichever comes first. Evinrude E-TEC models have a longer schedule – 3 years/300 hours in fresh-water with fresh-water recreational use. Boaters in salt-water areas and those in commercial usage or high performance boating have shorter service periods because of the corrosive nature of seawater and the heavier duty operating conditions. A 4-stroke may require 50 hours or 6 month interval oil changes if the motor is run at low speeds (trolling) or high speeds for extended periods of time. If it has an “extended warranty,” in order to keep it valid, most contracts state “…the engine must be maintained per manufacture’s recommendations.” Keep in mind that the whole rig should be visually inspected for overall condition and what service needs are to be recommended.
Types of usage (commercial, high-performance, etc.) and environmental conditions (salt, muddy, or shallow water) determine the type and the frequency of service needed. Discuss water pump and thermostat servicing with your customer. This also depends on operating conditions and type of use as well as engine hours.
Do not attempt to service without the correct service manual, tools, supplies and a thorough understanding of the procedures. Use common sense and observe safety precautions around moving parts, flammable liquids, and high voltage ignitions. With both 2-stroke and 4-stroke engines, each particular outboard is different and may have additional items that have to be addressed. This article is only an overview of servicing procedures.
INSPECTION and PROPELLER The first step is a complete visual inspection of the motor along with the steering system and control cables and other boat systems. Check hoses for deterioration and inspect everything for leaks and for worn, damaged or missing items. Remove the propeller and look for fishing line in the seals. Timing belts, air filters and alternator belts are some additional inspection items along with belt tensioners and pulleys that various outboards have. Props should be rebuilt or replaced if damaged to prevent harmful vibrations from affecting the outboard. For safety, leave the propeller off until all the servicing is completed. Check and replace the zinc anodes if needed. Some 4-strokes use internal cylinder block anodes for cooling system corrosion protection.
SPARKPLUGS and IGNITION Remove the plugs and lay them out in order; note if any one sparkplug looks significantly different from the others. A good plug has sharp edges on the side and center electrodes with no rounded or eroded areas. Flakes of carbon mean a possible rich running, poor oil quality, leaking injectors, or open thermostats. A tan center ceramic is ideal, but in outboards, the color can vary from off white to almost black. Always check for the outboard manufacture’s latest plug recommendations since changes may have taken place since a manual was printed. Evinrude FICHT and E-TEC engines require an additional step of positioning (indexing) the plug gap within 90° on either side of the fuel injector nozzle centerline.
Ignition output is important for quick starting, smooth idling and good acceleration. Perform the procedures outlined in the service manual using the proper tools. If the spark is weak or not consistent, find out why before going any further. Inspect the wiring, coils and connections for carbon tracks or deterioration. Replace and gap the sparkplugs if needed.
COMPRESSION A compression test indicates the internal condition of the motor’s pistons, cylinders and rings. Use a quality gauge and record the readings. Most manuals do not list the compression pressures but recommend results within 15% of each other on a healthy engine. Some Yamaha and Johnson-Evinrude outboards have staggered compression ratios so the bottom cylinders could have lower readings than the upper ones, but they should be close from side to side. A scored cylinder or piston may give a good reading at times because of residual oil sealing the grooves. Occasionally a low cylinder will improve after using a carbon-cleaning compound that frees up the stuck piston rings. This is a good time to torque the head bolts while the motor is cold if applicable.
Perform a leakdown test on 4-stroke engines as that is the only true test of those motor’s internal health. By listening to air coming out of the intake, exhaust, or crankcase it is easy to determine the source of leakage on a cylinder and piston that does not hold at least 90% of the air from the tester.
GEARCASE Drain the lower unit oil. If clear water comes out or metal chips are seen, the gearcase should be disassembled and inspected. Metal “fuzz” on magnetic drain plugs is normal, but chunks or chips are not. Use the manufacture’s recommended lubricant and refill from the lower hole until oil appears at the upper threads. New gaskets or o-rings under the screws assure a tight seal. Inspect the prop shaft for wobble and the seals for damage or fishing line. Grease the splines to prevent corrosion and a stuck prop. Install a new cotter-pin if applicable.
LUBRICATION Lubricate all the fittings with approved marine grease. Hood latches and other sliding parts work easier with a slight film of lube. Use silicone spray on carb linkages, contrary to the glob of grease that some factories recommend. Avoid spraying around the starter drive to prevent it from slipping. If you have a fuel injected Yamaha OX66, keep silicone away from the oxygen sensor located on the starboard side. Use care with a petroleum-based coatings if you spray it on the engine for corrosion prevention. Sparkplug wires, rubber and plastic could be affected. A greasy film will attract dirt and grit, plus it makes future servicing a sticky messy ordeal. You will spend extra time and shop rags cleaning off your hands and tools quite often to keep fingerprints from the boat’s upholstery, trim, and gelcoat.
4-strokes require and oil and filter change which is best done while the motor is warm. An experienced technician will soon learn a servicing sequence that will maximize his efficiency in performing the tune-up procedure in the shortest amount of time. For best results use an FC-W certified 4-stroke outboard oil if you do not use the manufacturer’s oil. That way it prevents any question of improper lubricant use should a warranty situation arise down the road.
LINKAGE Synchronization of the spark timing to the throttle opening and the removal of the carb or throttle body linkage free-play are known as “sync and link” adjustments. Service manuals show detailed step by step instructions because of the importance of these settings for a smooth running motor. Do not overlook the oil pump linkage adjustments on certain 2-stroke engines.
Electronic fuel injected motors may require a throttle position sensor (TPS) adjustment using a digital voltmeter. Again, follow the manual exactly for this critical setting.
WARNING SYSTEMS Test the integrity of the alarm systems. With the key on and motor off, disconnect the temp sender wire connector and ground it with a test lead. The warning horn should sound. On System Check gauges, the overheat LED will illuminate but the buzzer will not activate unless the motor is running. It is wise to test oil pressure switches and water-in-filter sensors if equipped per the service manual. Digital dash gauges may have different procedures.
FUEL and OIL Using a clean glass jar to inspect a fuel sample from the engine. It should be clean and clear with no debris, water or varnish smell. A turkey-baster works well for sampling the bottom of a remote oil tanks for sludge, water, or gelled oil. The engine mounted tanks on V4 and V6 Yamahas collect condensation in a 2” clear hose and should be examined regularly. Suzuki and Yamaha recommend the annual replacement of the oil filter assembly between the tank and the oil pump.
Replace and/or clean all boat mounted and motor mounted filters. If there is no boat mounted fuel-water separator, suggest one for your customer and emphasize its importance with today’s ethanol fuels which attract moisture. Pour the correct amount of a fuel additive into the gas tank to help clean out the system and to stabilize the fuel. This is very important if ethanol E-10 gasoline is used. Inspect the condition of the hoses, clamps, and any fuel valves.
ELECTRICAL SYSTEM Use an ammeter in conjunction with a voltmeter to test the electrical system. Crank the engine for about 15 seconds with the kill switch removed. A healthy battery will show 10 volts or more during cranking or test it with a quality load tester. Make sure the battery terminals and cable ends are shiny clean and replace any wing-nuts with regular nuts and lock-washers for secure connections. Distilled water is recommended for topping off regular batteries. According to ABYC standards the positive terminals should be protected with vinyl covers if the battery is not mounted in a covered box and the battery is to be securely tied down so it will not move around in rough water.
Start the motor and monitor an inductive ammeter to read the charging output. Compare the results with the service manual specifications. On computer controlled outboards, download an engine report from the ECU and save it with the customer service records. Technically oriented owners may want a copy for themselves. Check for any error codes and correct any recent abnormal indications.
TIMING and TEMPERATURE Set the carb-pickup timing or engine idle timing according to the service manual in addition to the linkage adjustments. Thermostat operation can be checked with an infrared temp gun or the finger method. If you can hold your fingers on top of each cylinder head for more than 3 full seconds, chances are that the engine is not warming up enough for proper operation. CARBON CLEANING Periodic use of a carbon remover is essential to long outboard life by keeping the rings and the pistons free of accumulated combustion byproducts on both 2-stroke and 4-stroke outboards. Cleaners like Mercury’s Power Tune, Yamaha’s Combustion Cleaner, or Evinrude’s Engine Tuner have instructions on the can. After waiting the recommended amount of time, run the engine for at least 15 minutes at low speed to clean things out before applying full power. Do this before changing engine oil and filter in a 4-stroke. For even better cleaning, add the proper quantity of a fuel additive carbon cleaner to the gas tank according to the manufacturer’s policies.
FINAL ADJUSTMENTS Idle speed and carb adjustments (if equipped) must be done in the water for proper exhaust backpressure, not on a hose flusher. Use an accurate tachometer and be patient while getting everything “dialed in” perfectly. Some multi-carb and certain EFI engines may need intake vacuum balancing for a smooth and consistent idle. Do not overlook valve adjustments that may be required at specified intervals. Although they are not often part of a regular tune-up, they are an important procedure affecting the drivability and longevity of a 4-stroke outboard.
Run the boat at all speeds after carefully setting the full throttle timing if required. Check that the top operating rpm is within the upper half of the factory recommended range for best performance. read less