Yamaha F50 Service Manual
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62Y3A111-16 1 2 3 4 5 6 7 8 I Operation When the throttle is opened suddenly, diaphragm 1 (via the link that is connected to the throttle lever) operates to pressurize the air in the pump chamber. The pressurized air opens diaphragm 2, and becomes distributed to the carburetors by passing through the pipes that are connected to the carburetors. The pressurized and distributed air then utilizes the passage of the main air jet to flow into the main nozzle. The pressure of the air helps suck fuel from the main jet, which increases the fuel in the main nozzle, and thus achieves the fuel enrichment. 1Main air jet 2Main nozzle 3Main jet 4Throttle valve 5Pilot screw 6Pilot outlet 7Pilot jet 8From acceleration pump 9Throttle valve closing 0Throttle valve openingADiaphragm 1 BDiaphragm 2 CTo carburetors ÈAir flow ÉThrottle valve opening direction 90 1 2 31 6 5 4 8 372 A BA B C S62Y1300 : : Technical tips
GEN INFO General information 1-1762Y3A11 Ignition system In order to determine the optimal ignition timing that is necessary for the proper operation of the engine, the built-in microcomputer in the CDI unit detects the signals from various types of sensors and controls the ignition timing in accordance with a control map that is based on those signals. The microcomputer also effects controls to protect the engine against overheating, over-revolution, and oil pressure drops, as well as to control warning devices. 1Pulser coil 2Flywheel 3Charge coil 4CDI unit 5Microcomputer6Ignition coils #1 and #4 7Ignition coils #2 and #3 8Oil pressure switch 9Thermoswitch Flywheel Three protrusions for the pulser coil are provided along the periphery of the flywheel. The purpose of these protrusions is for detecting the engine speed. Two of them are used for ignition signals, and one is used for identifying the cylinders, and these signals are transmitted to the microcomputer. 134 56 7 8 9 2 S62Y1310
62Y3A111-18 1 2 3 4 5 6 7 8 I Pulser coil The pulser coil transmits the pulser signals, which are generated in the pulser coil in accordance with the rotation of the flywheel, to the CDI unit. Among the two protrusions that are provided for generating signals, one is used for cylinders #1 and #4, and the other for cylinders #2 and #3, thus enabling the pulser coil to simultaneously ignite two cylinders. To provide ignition signals to the cylinders, the microcomputer determines the ignition cylinder and ignition timing. These are based on the cylinder identification signals generated by the protrusion for identifying cylinders, and on the pulser signals generated by the protrusions for generating ignition signals. 1Flywheel 2Rotating direction 3Protrusion for cylinders #1 and #4 4Pulser coil 5Cylinder identification protrusion 6Protrusion for cylinders #2 and #3 2 1 654 3 S62Y1320 Technical tips
GEN INFO General information 1-1962Y3A11 Ignition timing control Control circuit diagram Basic control The ignition timing is determined by using the map based on the engine speed (r/min). Then, igni- tion signals are output from the microcomputer in accordance with the ignition timing map so that ignition can take place at the optimal timing in relation to the engine speed. Then, the microcom- puter corrects the ignition timing in accordance with the operating conditions of the engine as detected by the signals that are input from the engine temperature sensor and oil pressure sensor. The pulser signals that are output when the protrusions for cylinders #1 and #4, and for cylinders #2 and #3 pass by the pulser coil, are used to calculate the engine speed. In addition, the pulser sig- nals are used to determine the forecast starting position of the ignition timing. 1Cylinder identification protrusion 2Pulser coil 3Protrusion for cylinders #1 and #4 4Protrusion for cylinders #2 and #3 5Pulser coil signal6Cylinder identification signal 7Identification signal for cylinders #1 and #4 8Identification signal for cylinders #2 and #3 9Rotating direction S62Y1330 Operation Positive start Quick acceleration Damage prevention Detection Microcomputer Engine start Engine temperatureIgnition timing control (optimized ignition timing) Engine speed control Warning buzzer (in remote-control unit) Warning lamp (low oil pressure) Warning lamp (to overheat) Engine speed Oil pressure Acceleration Over-revolution Low oil pressure Overheat 2 34 8 7 S62Y13406 9 1 5
62Y3A111-20 1 2 3 4 5 6 7 8 I Starting control When starting the engine, the timing is set to 5° BTDC until the crankshaft speed maintains 600 r/min for two seconds or longer. 1Cylinder identification protrusion 2Protrusion for cylinders #1 and #4 3Pulser coil 4Protrusion for cylinders #2 and #3 5Pulser coil signal 6Cylinder identification signal7Starting signal (5° BTDC) for cylinders #1 and #4 8Starting signal (5° BTDC) for cylinders #2 and #3 9Rotating direction Warm-up control After the starting control is completed, the control transfers to the ignition timing based on the warm- up map for three minutes. From the time the three-minute warm-up control has been completed, the control transfers to the normal map. 1Ignition timing (BTDC°) 2Engine speed ( × 1,000 r/min) 3Warm-up map 4Acceleration map 5Normal map 3 8 7 S62Y1350 24 6 9 1 5 123456 S62Y1360 3 4 5 1 2 5 0 Technical tips
GEN INFO General information 1-2162Y3A11 Acceleration control This control is activated when the throttle valve is opened suddenly. If the engine speed increases more than the specified figures, the control of the ignition timing transfers to the acceleration map. Thereafter, the control of the ignition timing transfers gradually to the control map before accelera- tion. If it was under warm-up control, the timing transfers to the warm-up control map, and if it was under normal control, the timing transfers to the normal control map. The control described above will be repeated if the engine is accelerated again. Over-revolution control This control operates by detecting the engine speed. If the engine speed increases to over 6,200 r/min, the ignition of cylinders #1 and #4 is stopped in order to regulate the speed. If the engine speed increases further to over 6,300 r/min, the ignition of cylinders #2 and #3 is also stopped. This control will not be deactivated until the engine speed drops below 6,200 r/min. Overheating control This control operates in accordance with the engine temperature, which is detected by the signal that is input from the thermoswitch. When the microcomputer detects via the thermoswitch signal that the engine temperature has increased to over 80 °C (176 °F), it outputs a signal to stop the igni- tion of cylinders #1 and #4, if the engine speed is over 2,000 r/min. At the same time, the microcom- puter issues a warning by operating the warning lamp and the warning buzzer. When the overheating control is activated, it will not be deactivated until the engine is stopped or the engine temperature decreases to under 70 °C (158 °F). The determination of overheating stops when the engine is stopped. However, until the engine tem- perature decreases to approximately 70 °C (158 °F) or below, the overheating control will be acti- vated upon restarting the engine. Upon restarting, if the engine speed is under 2,000 r/min, the overheating control will not be activated for 75 seconds. However, if the engine is operated at over 2,000 r/min for more than 25 seconds, the overheating control will be activated. Oil pressure control The oil pressure control operates in accordance with the signals from the oil pressure switch. The oil pressure is determined to have dropped if the engine continues to operate at over 2,000 r/min with an oil pressure of under 49 kPa (0.49 kgf/cm 2, 6.97 psi) for more than one second. When the oil pressure control is activated, the warning buzzer sounds and the warning lamp illuminates. If the engine speed is over 2,000 r/min, the control stops the ignition of cylinders #1 and #4 so that the engine speed will not increase to over 2,000 r/min. Once an oil pressure drop is determined, this control will not be deactivated even if the oil pressure recuperates, until the engine is stopped.
62Y3A111-22 1 2 3 4 5 6 7 8 I Power trim and tilt The newly designed power trim and tilt consists of an up-main valve, a down-main valve, an up- relief valve, a single cylinder, and a single ram, which control both trim and tilt functions. The power trim and tilt cylinder has been integrated with the gear pump housing, the reservoir tank, and the power trim and tilt motor in order to achieve a smaller and more compact unit. Hydraulic system diagram 1Power trim and tilt cylinder 2Ram 3Reservoir 4Manual valve 5Down-main valve 6Down-relief valve 7Hydraulic pump 8Up-relief valve 9Up-main valve 12 4 5 6 3 7 3 8 93 S62Y1370 Technical tips
GEN INFO General information 1-2362Y3A11 Power trim and tilt components 1Cylinder 2Ram 3Check valve 4Down-main valve 5Down-relief valve 6Motor 7Gear pump 8Up-main valve 9Reservoir 0Manual valveAUp-relief valve BUp-shuttle piston CDown-shuffle piston DTrim cylinder base EFree piston FTilt piston 2 3 546 7 8 9 0 A B 9 C D E F 1 S62Y1380
62Y3A111-24 1 2 3 4 5 6 7 8 I Trim-up function The gear pump pumps power trim and tilt fluid to the up-main valve. As a result, the fluid pressure opens the up-shuttle piston causing the fluid to flow into the lower part of the power trim and tilt cyl- inder. At the same time, vacuum from the gear pump opens the down-main valve and down-shuttle piston, which causes fluid from the upper part of the power trim and tilt cylinder to return to the gear pump, and also sucks fluid in through the reservoir. The pressurized fluid forces up the trim cylinder along with the tilt piston, free piston, and trim cylin- der base. As the trim cylinder moves up, the ram extends and the outboard motor is trimmed up. The end of the trim range is when the trim cylinder tops out in the power trim and tilt cylinder. Trim-up function 1Power trim and tilt cylinder 2Ram 3Trim cylinder 4Down-main valve 5Motor 6Gear pump 7Up-main valve 8Reservoir9Up-shuttle piston 0Down-shuttle piston AFree piston BTrim cylinder base CTilt piston ÈReturn ÉSend : : S62Y1390 12 3 45 6 7 8 9 8 0 A B C Technical tips
GEN INFO General information 1-2562Y3A11 Trim-down function When the power trim and tilt switch is pressed to “Down”, the motor turns the gear pump counter- clockwise and the power trim and tilt fluid flows in the opposite direction to that of the trim-up func- tion. Tilt-up function When the trim cylinder tops out, the check valve is pushed down by the end screw wall. This causes the ball in the check valve to move down, opening the fluid passage and allowing the power trim and tilt fluid to flow from the upper part of the trim cylinder, through the down-shuttle piston and the down-main valve, and back to the gear pump. In addition, fluid is also sucked in through the reser- voir and the pressurized fluid continues to flow into the lower part of the trim cylinder, pushing up the tilt piston and free piston, and further extending the ram. As the tilt piston moves up and off of the trim cylinder base, the base moves up and pushes the balls outward to fit into holes of the power trim and tilt cylinder. Once the balls have been fitted into the holes the trim cylinder base cannot move. The end of the tilt-up range is when the tilt piston tops out in the trim cylinder and the ram is fully extended. The tilt-up function operates when the fluid pressure is under 10 MPa (100 kgf/cm 2, 1,423 psi). When the fluid pressure in the lower part of the trim cylinder increases to over 10 MPa (100 kgf/cm 2, 1,423 psi), the up-relief valve opens and allows the pressurized fluid to flow into the reservoir. Thus, the tilt piston and free piston are not pushed up and the ram cannot be extend further.