125 hp Mercruiser engine

Question
I bought a cottage earlier this year which came with a 1989 Larson bowrider with a 2.5 liter 125hp Mercruiser engine.  I have used it a few times this year and it has run well at high speeds and a little rough at low speeds.  It often stalls when idling.  I took it out yesterday and it was running well as I was towing people on a tube.  I changed riders and had it moving slowly forward to tighten the line and when the line was tight I gave it some gas.  It started out fine but suddenly stopped moving forward and the engine changed to a much higher whine than usual.  It sounds like something came disengaged.  The engine starts fine and runs, but has a higher pitch than usual.  It will not go in forward or reverse.  I didn't hit anything and nothing is caught around the prop.  Unfortunately, I had to leave soon after we paddled back to shore and can't get back to look at it until next week.  Any thoughts?

Answer
Hi Steve...Thank you for selecting the undersigned to reply to your question.

Usually, when an engine doesn't run smoothly at low rpms/speed, the choke or air mixture requires adjustment. However, with no fwd/rev at all, there's likely a gear problem in the lower unit, and maybe its the pinion gear. You won't know till the lower unit is dismantled.

Safe Boating
Ron