shift shaft troubleshooting

[sti1471]

I got a alpha one stern drive. I have the lower unit off the boat and I can see the prop shaft, and the shift shaft. The guy I bought the boat from said that the shift shaft was most likely the issue the boat will go in forward gear, but not reverse.

I hope I can explain this right.

With the lower unit off the boat, I can turn the prop CW and I can watch the prop shaft turn with the prop. When I turn the prop CCW the prop shaft does not turn. Since the lower unit was taken off the boat in "forward" position, do I need to manually shift the lower unit into reverse to get the prop shaft to turn with the prop spinning CCW?

The teeth on the lower shift shaft are a bit worn but I want to make sure the shift shaft needs to be replaced before I replace it. When I put my fingers on the top of the lower shift shaft and turn it, I can turn it in either direction about 1/4" before it feels as though the gears are locking as it should I would think.

How do I manually test the lower unit with i removed from the boat to verify the shift shaft is bad or good? Are there any other tests I can do while the lower unit is off the boat to determine a possible cause if the shift shaft is not the issue?

 

[Fishermark]

Re: shift shaft troubleshooting

You can check the shift spool to see if it is worn out or not. Here's a video I made showing the test. If the splines are worn out, then yes, you will need to replace the shift shaft. But I would certainly check the shift spool as well. (The manual has a paper gauge that you can print out and use for the test).