The following systematic checks should be made in mid-season or every 50 hours:
1. Clean and re-gap spark plugs to recommended gap. Replace worn or burnt spark plugs according to manufacturer's recommendation. (Use new gaskets, when possible, and torque plugs to manufacturer's recommendations) Do not attach plug leads until engine is to be tested.
2.  Tilt the engine slightly forward.  Loosen upper gearcase drain plug, but do not remove completely. Carefully remove the lower gearcase drain plug, watching for a, sometimes, small drop of water that comes from the gearcase. If there is water or the lube itself is milky, there is water mixed into the lube and a seal repair is mandatory. If it is not milky, check for metal particles in sample and on the magnetic drain plug, if it has one. Very powdery material could be on the magnet, but no chunks when you rub the accumulation between your fingers. Remove upper plug. After draining, verify amount drained out, in respect to the amount required, by your owners manual. Keep in mind that depending how warm the lube is, not all will drain out, if the unit is very cold) If all seems OK.... Drain and lightly flush gearcase with fresh lube. Refill to correct level using manufacturer's recommended lubricant.
3. Remove and Check propeller for correct pitch, wear, chipped, or badly bent blades, and rubber hub for excessive overheating.  Inspect forward and reverse thrust washers and the nut and it's retainer for wear. Excessive wear usually means the prop was loose during operation. (see owners manual for torque spec)  Check shaft seal damage from mono -filament fishing line.
4. Lubricate all grease fittings, using manufacturer's recommended lubricant. And while your greasing around the motor mount and swivel area, be sure to check the torque of your motor mount bolts.
5. Lubricate all carburetor and magneto linkages with manufacturer's recommended lubricant.
6. Check carburetor and ignition synchronization per manufacturer's specifications.
7. Remove and clean fuel filter. Where applicable, replace fuel bowl element.      (Always use new filter bowl gasket.)
8. If applicable, Adjust tension on magneto and/or generator drive belts, 1/4 to 3/8 inch play is sufficient using light pressure near center of belt.
9. Clean and coat battery terminals with grease, or special protective compound. Check fluid level and specific gravity. Check battery hold down for wear and corrosion.
10. Check remote control box, cables and wiring harness for fastening security, wear or binding. Is the key switch tight in the case?
11. Check steering controls for condition and connection security. Lubricate mechanical steering with an anticorrosion lubricant.
12. Connect plug leads and start engine. Never run engine out of water. Check water pump and thermostat operation.
13. Check carburetor adjustment per manufacturer's specifications. 
Note: Do not try to readjust carb settings when the boat is out of the water. The pressure on the exhaust system, when the engine is submerged, is calculated into the calibration of most outboard motors.
14. While running with cowl removed, look for any signs of leaking fluids or smoke coming from inside the cowl area. Pay special attention the area under the flywheel, and powerhead base where end seal leaks occur. There should be no leaks under a cowl.

OFF-SEASON STORAGE
Add fuel stabilizer to motor fuel supply.

Operate motor in test tank, or on boat, at part throttle with shift lever in neutral. Rapidly inject rust preventative oil into carburetor air intake, or intakes, until motor is smoking profusely. Stop motor immediately to prevent burning oil out of cylinders. This will lubricate and protect internal parts of powerhead while motor is in star age. If motor was last operated in salt water, run it in fresh water before preparing it for storage.
1. Place motor on a stand in normal upright position. Remove motor cover.
2. Retard throttle all the way and disconnect spark plug leads. Rotate motor fly-wheel several times to drain the water from water pump. The electric starter may be used.
3. Clean and lubricate electric starter drive mechanism. Do not oil shaft since it may run down into motor brushes.
4. Remove propeller and check for condition and pitch. Inspect for burr at drive pin holt and shift seal damage from mono-filament fishing line. Clean and liberally lubricate propeller shaft. Renew propeller drive pin if bent or worn. Reinstall propeller using new cotter pin or tab lock washer.
5. Drain and refill gearcase, using the manufacturer's recommended lubricant.
6. Wipe over entire internal motor surface with a clean cloth soaked in light oil. Apply a good quality automotive wax to the motor cover.
7. Store in an upright position in a dry, well ventilated room. To prevent accidental starting, leave spark plug leads disconnected.
8. Remove battery from boat and keep it charged while in storage. Store in a cool well ventilated area. Do not store on concrete.

PRE-SEASON PREPARATION
1. Remove, clean, inspect and properly gap spark plugs. Renew defective plugs. (torque plugs to manufacturer's recommendations.)
2. Remove oil level plug from gearcase and check for proper oil level.
3. Thoroughly clean and refinish surfaces as required.
4. Check battery for full charge and clean terminals. Clean and inspect battery cable connections. Check polarity before installing battery cables. After cables are installed, cover cable connections with grease or special protective compound to prevent corrosion.
5. If possible, run motor in test tank prior to installing on boat. Check water pump and thermostat operation.