motor problems

[MR.T]

I have a 1982 mercury outboard 80 hp. I just changed the lower unit on it but as soon as I start the boat It looks as if it is in gear right away tried putting it into reverse and nothing happpens anybody here have a clue what my problem is??

 

[jfm]

I have a 1982 mercury outboard 80 hp. I just changed the lower unit on it but as soon as I start the boat It looks as if it is in gear right away tried putting it into reverse and nothing happpens anybody here have a clue what my problem is??

I've removed/replaced that lower unit many times and best guess from your post is that you have probably misaligned the shift shaft when you reassembled it. No big deal and easy to fix.

The FNR gear selection is done by a shaft (called the "shift shaft") that runs down the leg of the engine in front of and parallel to the drive shaft. At the top inside the powerhead there is a 3 inch long tiller arm on the shift shaft and your control cable pushes/pulls this tiller. That rotates the shaft +/- 45 degrees and in turn that selects FNR

When you drop the lower unit off, the shift shaft splits at a splined joint. The splines are coarse, only 6 of them. If you reassemble and you are one spline out, you get exactly the problem you describe. To cure this:

1. Remove the lower unit again, or at least drop it down 6 inches
2. Set the control lever and the tiller at the mid point of their travel ie neutral
3. Twist the stub of the shift shaft in the lower unit until you have selected neutral inside the gearbox - you can easily tell you are in neutral because the prop shaft can be turned and the drive shaft stays still and vice versa. You can also feel the full angular stroke of the shift shaft stub in the lower unit and then place the shaft at the midpoint. You have to do this a bit by feel
4. Then reassemble with plenty of grease on the spline, and it will be fine

The top half of the shift shaft and its tiller arm are at bottom of first pic below, part 14. The spline that you have misaligned is at bottom of that shaft.

Part 39 in the second pic below is the lower half of the shift shaft that has the spline at the top. Both pics courtesy of the excellent boats.net

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[MR.T]

thanks will try. I will get back to you if it works hopefully it does