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Possible To Manually Steer Motor

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  • #16
    Originally posted by boscoe99 View Post
    It was not moving because you were not being manly enough about it.

    It would not be harmful to the steering system to steer the motor manually. Enough fluid remains within the system to keep everything lubricated. The only harm may come to your muscles, which may quickly tire moving the boat in one direction, but as you note, not the other.

    What you were feeling is caused by what is referred to as "P" factor. If the propeller shaft is not perfectly parallel with the water line (say the engine is trimmed downward a tad) then the blade moving downward has a greater angle of attack than does the blade going up. The greater angle of attack will tend to move the back end of the motor around to the right. With a normal gear case that is. The front of the motor turns to the left. The boat then wants to turn to the right.

    If the motor is trimmed up such that the propeller shaft is not parallel, then the effect is just the opposite. Which is why motors come with anode trim tabs. Which is why the tab is normally turned to the right, to try and counter "P" factor.

    Do this in your own boat. Get onto plane starting with motor trimmed fully downward. Don't trim it us. Get up to speed. Turn right. Then turn left. It will be easier to turn to the right than the left. Now trim the motor up well beyond your normal trim angle. Turn right. Then turn left. It should now be easier to turn to the right than to the left.

    Now think of a single engine airplane having long long propeller blades. The turning force is much greater. On take off and climb out the crankshaft of the engine is angled upwards going towards the front. The propeller blade on the right hand side coming downward will try like hell to turn the airplane to the left. The pilot has to push like heck on the right rudder pedal to keep the airplane straight. If he has rudder trim then he can use that to move a tab on the rudder to do the work for him. Of course when he levels out in cruise he has to either readjust the trim tab or he has to stop pushing on the right rudder pedal.

    Awesome details, makes sense now. Dam rats, them sonsabitchs can chew through almost anything.
    Jason
    1998 S115TLRW + 1976 Aquasport 170

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    • #17
      Many of the WW2 fighters had this problem. Running a big prop with a lot of HP they could flip right over when they would get light on the gear on take off. Small rudder on them and not enough opposite aileron inputs could not over come the torque of the prop.

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      • #18
        Originally posted by panasonic View Post
        Many of the WW2 fighters had this problem. Running a big prop with a lot of HP they could flip right over when they would get light on the gear on take off. Small rudder on them and not enough opposite aileron inputs could not over come the torque of the prop.
        The story I always heard was that the P-51 had so much torque that the throttle could not be opened wide open quickly. Otherwise the airplane would not be con*****able. Throttle was added slowly until airspeed was sufficient to counter the propeller torque and P factor. An airplane being flown by an 18 year old. With less than maybe 100 hours flight time. Who's life expectancy was what, less than 25 missions?

        Here kid are the keys to the airplane. Try to kill someone before someone can kill you.

        Those were some tough dudes.
        Last edited by boscoe99; 06-27-2017, 08:19 AM.

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