Yamaha 40-HP Gear Shift
Posted: Fri Feb 05, 2021 3:38 pm
I bought a 1988 Yamaha 40-HP two-stroke-power-cycle for use on a Boston Whaler boat I am restoring. The engine seller ran it [for] me in his driveway with the lower unit in a barrel of water, and it seemed to work fine. I'm am almost sure he shifted it into forward and reverse during the test.
Later, at home, I noticed the engine steering arm [tiller] was rusty, and thought about replacing it. It's a complicated job involving removing the power head and the lower unit. I got as far as partially removing the lower unit, and decided that this was more work than I wanted to do. So, I sanded off the rust and painted it.
When I re-connected the lower unit, I may have screwed up something. I have only tested it on the stand, without firing up the engine. The symptom is that when shifted into forward, the prop spins freely by hand and there is a "clacking" rotational sound. When I turn the crankshaft by rotating the flywheel clockwise, the prop turns clockwise as it should. But, I can also turn the prop clockwise by hand easily, as easily as I can turn it when it is in neutral. With the addition of the clacking noise. When this is going on, the crankshaft is not moving and the engine is not turning over. In forward, the prop will not turn counterclockwise by hand.
Neutral seems normal. [Something, possibly the propeller] turns freely without any noise.
Reverse seems normal. The propeller will turn counterclockwise when the flywheel is rotated in a clockwise direction. It will turn by hand if you overcome the resistance of the compression of the engine, but does not turn freely, and doesn't make the clacking noise. When in reverse, will not rotate clockwise by hand.
Hard to tell if the sound is coming from the mid-section or the lower unit. Sounds like both.
Just to be sure, I took the lower unit off completely and then re-attached it, following the manual. The problem problem [that is, the observed behavior] did not change.
I don't know if this is likely that the problem is upper, where the driveshaft connects to the crankshaft, or lower, where the shift into forward gear may be not happening fully.
[Apparently is soliciting advice on "the problem" and its remedy.]
Later, at home, I noticed the engine steering arm [tiller] was rusty, and thought about replacing it. It's a complicated job involving removing the power head and the lower unit. I got as far as partially removing the lower unit, and decided that this was more work than I wanted to do. So, I sanded off the rust and painted it.
When I re-connected the lower unit, I may have screwed up something. I have only tested it on the stand, without firing up the engine. The symptom is that when shifted into forward, the prop spins freely by hand and there is a "clacking" rotational sound. When I turn the crankshaft by rotating the flywheel clockwise, the prop turns clockwise as it should. But, I can also turn the prop clockwise by hand easily, as easily as I can turn it when it is in neutral. With the addition of the clacking noise. When this is going on, the crankshaft is not moving and the engine is not turning over. In forward, the prop will not turn counterclockwise by hand.
Neutral seems normal. [Something, possibly the propeller] turns freely without any noise.
Reverse seems normal. The propeller will turn counterclockwise when the flywheel is rotated in a clockwise direction. It will turn by hand if you overcome the resistance of the compression of the engine, but does not turn freely, and doesn't make the clacking noise. When in reverse, will not rotate clockwise by hand.
Hard to tell if the sound is coming from the mid-section or the lower unit. Sounds like both.
Just to be sure, I took the lower unit off completely and then re-attached it, following the manual. The problem problem [that is, the observed behavior] did not change.
I don't know if this is likely that the problem is upper, where the driveshaft connects to the crankshaft, or lower, where the shift into forward gear may be not happening fully.
[Apparently is soliciting advice on "the problem" and its remedy.]