Start motors and monitor performance for signs of malfunctioning, such as smoke, excessive vibration, or misfiring. Document inspection and test results and work performed or to be performed. Mount motors to boats and operate boats at various speeds on waterways to conduct operational tests. Repair engine mechanical equipment, such as power tilts, bilge pumps, or power take-offs. Perform routine engine maintenance on motorboats, such as changing oil and filters. Replace parts, such as gears, magneto points, piston rings, or spark plugs, and reassemble engines. Idle motors and observe thermometers to determine the effectiveness of cooling systems. Inspect and repair or adjust propellers or propeller shafts. Adjust carburetor mixtures, electrical point settings, or timing while motors are running in water-filled test tanks. Set starter locks and align and repair steering or throttle controls, using gauges, screwdrivers, or wrenches. Disassemble and inspect motors to locate defective parts, using mechanic's hand tools and gauges. Adjust generators and replace faulty wiring, using hand tools and soldering irons. Repair or rework parts, using machine tools such as lathes, mills, drills, or grinders.