Trouble with Yamaha 150 outboard
 

I was out today fishing with the family and while heading home I hit a shallow area in the bay. I was running about 28mph and when we hit the shallow area we obviously slowed down and it pushed my outboard up as if I was trimming it up. The motor never shutoff and seemed to run fine during this whole process. Once clear of the shallow area the boat got back on plane just fine and ran home perfectly. When pulling into my marina I went to reverse into my slip but the motor would not shift into reverse. I tried multiple times and all it would do is rev up real high but no reverse. I could shift into forward and neutral with no issues. I tried doing a google search and have read anything from needing to replace the lower unit to it could just need a new hub inside the prop. I know I most likely need to have a mechanic check it out but was hoping someone on here may have some information for me as to what it could be. The motor is a 1993 Yamaha 150hp. I appreciate any help

Take the cowling off and make sure the cable is shifting into reverse

Hub not likely because yuo can go fwd but that can be checked with motor not running. Shift gears and spin prop by hand. Figure out if gear is shifting but prop spinning.

remove cowling and see whats happening when you shift. try to shift from there.
Get a sense of if it is shifting but not working or not really getting from N to R.

The linkage might have slipped or the rod down to the lower unit bent?

Another step would be drop lower unit and see if you can shift it.

Just an update. I went down to the boat today only had about 20min to check it out before work. The motor started up and ran fine and shifted into forward with no issues. I had the cowling of so I could watch the shift cables work. When I shift into reverse the cable moves as it should but most of the time it will not shift into reverse. I say most of the time because it did shift into reverse 3 times when I was trying today. The mechanic at my marina won't be able to take a look until later this week.

You did not say what year Yamaha. I know some of the older ones had shift shaft issues. Hopefully not your case, because fwd works.

disconnect shift cable and shift by hand.

If that works, you can readjust the cable until it works.

that is what I am thinking, just need to adjust the cable where it connects to motor

Okay another update. My father in law is a mechanic so he came down to the boat to see if he could figure it out. While at the boat it appeared the shift cable was not going all the way back into reverse so I helped and pushed it by hand and it shifted into reverse. After that it shifted into reverse everytime we tried. So we decided to go out for a quick cruise and while out I slowed down and went into neutral and when I went to get going again it wouldn't shift into forward. After multiple attempts of just going back and forth with the shifter it went into forward again and we went on our way. When pulling up to the dock I tried putting it in reverse and the motor rpm's went up real high and then it kind of slammed into reverse. I think it may be time for a new lower unit but I want to be sure before I purchase one. last thing I need is to order one and install it and find out it was the cables that went bad. Thanks for all the advice everyone I really appreciate it!

is the shift cable making full travel? Pull the cable loose on the engine end and see if it has any slop in it. If the cables have any age, go ahead and replace them.

Sound more like cables & linkage than your lower unit. Disconnect the cables and shift it by hand, that will eliminate half of the potential issues. If it won't shift (while running) then it may be the lower or the shaft but before I bought anything my next step (as other have suggested) is to simply drop the foot & check if it shift ok then, it's the only way to be positive it's in the gearbox.

Simple things first though, since it does shift, and the throttle is also part of the shifter I'd look there first.