Outdrive problem or motor?

[boaterdude83]

Coming into dock today, my engine was running perfect, smooth. Drove fine all afternoon. I was at around 1200 rpms, and it almost seemed like I hit somthing, or somthing tried to stop the prop. It happened twice more after that. My father also said he had it happen to him 2 nights ago while cruising at low speeds. He said it stalled the boat out, but it started right back up and continued on. The outdrive is used, but was in great condition. Oil was clean, and I just refilled it with synthetic oil. Could that possibly be the U-joints in the drive shafts? The outdrive had low hours on it, but sat for a while. Thanks everyone- Enjoy your boats!

Joe