Operation And Service Manual [Operating Instructions] [2017]

After making the initial motor-height setting, it is time to test run the boat. If cavitation occurs (air enters the pump, which causes loss of thrust and motor overrevving), then you must lower the engine 1/4" at a time until smooth operation is obtained.

If smooth operation is obtained with the initial set ting, you should raise the motor in 1/4" steps until cavitation does occur. Then lower the motor 1/4", and mark and lock that location. This height setting will never need to be changed, regardless of the load being carried.

CAUTION:
Slight ventilation on sharp turns or in rough water is acceptable, but excessive ventilation is harmful to both motor and pump and should be avoided.

The motor tilt pin should be set so the engine is in a vertical position when the boat is planing. If the boat rides bow-high or tends to be stern heavy, tilt the motor down one step. This will point the jet stream lower, giving added lift to the stern.

NOTE: If the tilt angle is changed, then the motor height must be rechecked.

The impeller is always engaged and produces a certain amount of thrust while the motor is running. “Neutral” is achieved when the reverse gate is in a middle position that balances forward and reverse thrust. Since the “Neutral” position on the shift control may not precisely balance the thrust, be sure to secure the boat to the dock or beach the bow of the boat during cold starts to avoid the possibility of being thrown off balance as the motor starts.

Except for low-speed maneuvering, do not use the reverse gate to slow or stop the boat; this will cause the motor to kick up and out of the water, similar to hitting a submerged object in a propeller-driven craft.

Experiment with steering your boat in an open area before attempting downstream river running. Remember when running downstream, your speed relative to the shore is the boat’s speed added to the speed of the river. You may find that steering response is slower than a prop driven craft due to the relatively flat-bottomed hull and lack of a skeg. The boat will tend to skid in turns. You must start your turns early and use sufficient power to maintain steering control.

WARNING
If you attempt too tight a turn at too high a speed, your boat could spin out or even roll over.

Maneuvering upstream is easier since the current speed and direction can be more readily countered. You can throttle back and maneuver your way through tight areas with good control. At narrow and potentially rough or hazardous passages, you should stop and study the layout. Look downstream so you will recognize it on the return trip. Once through a challenging spot, you may wish to run down and travel back up the same stretch to memorize the course you find to be the best.

If you are not sure of a tight area on a downstream run, it is better to drift through on the oars with the motor tipped up, or work the boat through on a rope.

The life of both impeller and water intake housing can be greatly increased by avoiding the intake of sand and gravel. Intake suction, acting on the bottom, will cause your jet drive to work like a dredge when the intake comes within 2 or 3 inches of the bottom. It is best to shut off the motor and drift up to the shore when landing, and to shove off with an oar when leaving. You can idle through areas less than 1-foot deep, but there should be more than 1 foot of water under the boat when opening the throttle for cruising or planing.

Once planing, boat speed will prevent sucking in gravel. While great suction exists at the water intake, your boat passes over the bottom so quickly that rocks, sand, and debris have no time to lift before the boat is beyond the disturbed area.

While boating in particularly shallow areas, remember that running on a full plane will make the boat ride higher in the water. This can allow you to travel through areas that might be impossible to traverse at slow speeds. Be sure you know the river bottom before attempting this. You should attempt planing only in areas where the bottom is sand or gravel. If you hit bottom where there are large underwater obstacles or sharp rocks, you may damage the boat and motor. If you do run aground, shut the motor off immediately and drag the boat to deeper water. Occasionally, when running aground, a small rock may lodge between the impeller and housing wall, and the motor will come to a stop. Neither starter motor nor starter rope will be able to turn it over.

To clear the obstruction, turn the flywheel counter clockwise (by hand with a rocking motion) or remove the six fasteners retaining the water intake housing and slide it off.

Any debris jammed between the impeller and casing will fall out. Attempting to turn the flywheel either direction may be personally too difficult due to the added torque required to overcome the valve train. Removing the intake will render the best results in most cases.

WARNING
Do not attempt to use a wrench on the flywheel locknut to rotate the flywheel backward because you may loosen the nut. Proper tightening, while afloat without the proper tools, is not possible, and major damage could occur to your motor.

WARNING
Be sure to remove the spark plug wires before removing the intake screen.

Be aware that gravel passing through the pump will wear and round off the leading edges of the impeller blades. For maximum performance, file these edges occasionally to keep them as sharp as when new (see Impeller in the Maintentance section).

Rough edges caused by rocks and gravel will lead to additional damage of the impeller if they are not removed by filing them off in some way. Turbulence across the blades behind these rough edges will result in low pressure areas that will allow small pockets of water to boil. These pockets of steam later collapse releasing a large amount of energy that erodes the impeller surface. Such damage spots are referred to as cavitation burns.

NOTE:
Your jet drive is equipped with a shear key to protect it in the event of a rock jam. This key can be located by removing the water intake housing and the drive shaft nut. Before replacing the key, note the position of the impeller shim washers, and replace them in the same order as removed. Tighten the impeller nut as described in the assembly section of this manual.

Occasionally, when either holding or proceeding slowly upstream in a fast-moving, shallow area, you will lose power. This is usually caused by suction holding flat rocks, lily pads, paper, or other debris against the intake grille and restricting water intake. If you quickly stop the motor and restart it, this sort of material will fall away and full power will be restored. If rocks have been jammed between the grille bars, turn off the engine and pry them out with a suitable tool.

If you tie your boat up at a sandy beach, where the action of waves causes the boat to rise and fall, be sure to tip the motor up out of the water. Failure to do this will result in the buildup of sand inside the intake housing and around the impeller. It is advisable to tie the boat up and shut off the motor any time it is likely not to be used for a sustained period of time.

As with any outboard, you will get maximum econo my by not running at full throttle. Running at one-third to one-half throttle, with the boat at a steep angle, leaving a large wake, will also waste fuel.

It is important for you to learn how to use the Power Trim and Tilt function properly, on those models equipped with this feature. The Power Trim and Tilt function is convenient for use while drifting, and when operating at low throttle in very shallow areas. When under power, however, the engine should not be trimmed out in an effort to gain speed as is done with conventional propeller-driven motors. When planing, the engine drive shaft should be either vertical or tucked under, toward the boat in order to provide a good scoop angle for the water intake grille. Tilting the motor outward, beyond a vertical position, reduces the scoop angle and can cause impeller slippage, as well as cavitation burns on the impeller blades. Manual-tilt models should be adjusted with the tilt pin to provide a vertical engine position while planing.

General

Occasionally, check all mounting bolts, intake screws, linkage connections, etc.; to be sure they are tight.

Bearing Lubrication

The need for frequent lubrication of your Yamaha Jet Drive Outboard cannot be overemphasized. Yamaha recommends lubrication after each day's use and every 10 hours of operation. Make greasing a regular part of your cleanup. Use only Yamalube Marine Grease or NLG1 greases.

CAUTION:
Do not use a pneumatic grease gun. Overpresurizing the grease chamber may cause the seals to move out of position.

The lubrication fitting for the drive shaft bearing is located at the top-left-front of the jet drive casing (see