Went out today and at slow idle right when you get ready to take off (fast idle) there is a knocking sound that sounds exactly like your hitting small stumps. A someone loud knock and jerk. Once you punch it and get on plane it stops. Never had this problem before and have no clue what it is. Any ideas would be helpful.

Have you changed your lower unit oil? I would check that before taking it out again.

Yes it was just changed when we had new water pump put on it back in October.

And then about 3 or 4 months before that too. Change it regularly.

shift cable adj ?

2nd adjust the shift cable toward forward.

I developed what sounded like the same problem with my 150. At first I thought the lower unit might be going away. Then I checked the prop shaft for excessive play and that was OK. There was a clunk going into gear and a second clunk as I added throttle. In addition a high-idle had developed. I was told the high idle could be a module on the engine. It started to give me that SICK feeling of seeing dollars go away.
Fortunately I was able to figure out how to adjust both the shift cable and the throttle cable at the engine. It wasnt that difficult and solved both problems.

Thanks guys. Gonna run it to the shop tomorrow. Hoping that's all it is. Makes me cringe when I hear it. I want it fixed.