87 force 125 won't engage from neutral to drive

I have a force 125 outboard, on a bayliner 18 fishing boat. this is my first real boat and I bought it about three weeks ago. first trip out it ran fantastic, just had to adjust carb slightly to keep idling. second trip out it was running great, ran out of gas, put gas and oil in it and it started right up but would no longer go into forward,motor would rev up, water bubbled and sprayed all over but we went no where. propeller seems to spin free in neutral and engages in forward, but only spins a very little bit even with engine running high. there is a slight clicking noise as the motor idles down but it is not coming from engine itself. also when it is running it dies almost immediately when you try and put it in reverse. almost as if the shaft locks up. any suggestions as to what this might be, simple or complex. like i said first boat and don't know where to even start.

Welcome.
First do a compression check then a spark check.
Check the gear oil for water/ rust or metal shavings.
On each carb is an air screw, it's for adjusting the fuel/ air mix at an idle.
Set both at 1 and 1/8th turn out from lightly seated.
Pull the screws out, they should be smooth and no cuts or grooves.

Not sure why the F gear won't engage but unhook the cable and try shifting by hand.
You can do this running but watch out for the prop and make sure there is plenty of water going to the unit.

Dying when going into gear: what's the idle set at? Should be about 1100 in N 800 in gear.
Drop the lower remove the pump and see if the shaft spins easier.

Where you located?

I had the same problem almost exactly as you described. After disassembling my lower unit I realized that my prop shaft busted in half.