I've lurked a long time, and finally need to post and use the vast
experience here. I had my 85 Chris Craft Scorpion (200 HP Mercruiser
Alpha) out for the last time Friday before winterizing it.

We were towing the kids on the tube, and on the last go-round, the wife
shut off the boat to let a little one in, started it up, dropped it into
forward, and we had no thrust. Reverse was a no-go either. We tried
to go just barely above idle to limp us back. I immediately thought
spun prop. We had encountered deep mud about 3 weeks ago and were stuck
for a short spell in it. Nothing doing on limping, and one tow later we
were back on dry land. (Thanks to the two fishermen who helped out if
you read this)

Back on land with muffs on, we started it up. The wife moved the gear
lever forward, and the prop did turn at proper speed for the engine (it
appeared). After returning to neutral and trying again, the prop did
not spin. Same for several attempts in forward and reverse. I drained
the oil (have to winterize it anyways sometime) and took the lower unit
off. I did have the gear selector in forward for the removal.

With the lower unit off, I turned the lower driveshaft. No prop shaft
spin. I manually turned the gear lever to reverse and tried. No spin
either when appropriate turning applied. If I manually hold the shift
shaft in as far forward it can go in forward, I can sometimes get the
prop shaft to spin, but I feel a slight 'tug' backwards as if the shift
shaft doesn't want to stay in that position. Sometimes the prop shaft
will spin, other times it will 'catch' a few teeth, and sometimes not at
all. Mostly not at all.

Problems/observations that may or may not have exacerbated this situation:

1) Tendency to shift 'slowly' from neutral to a drive gear. (I know,
I've since learned this is a bad habit)
2) About 5-10 sec of good engine throttle with the prop not spinning in
the water. (First time we noticed the problem.)
3) Do not know last time any gear work was done. Engine of boat has
1200 hrs. Drive fluid changed yearly.
4) Fluid had no water and no chunks of metal.
5) Water pump impeller housing looked used, but not spectacularly worn.
6) Encounter with shallow mud about 3 weeks ago, which abruptly stopped
engine. Lower unit flushed and prop cleaned out of clay based hard
packed mud. No other visible external damage.
7) Boat operated total of 7 hours from mud until now.

Questions:

1) Is it possible (better if someone has actually seen the lower unit
pinion and forward/reverse gears to be the weak link/problem here? I
would have been sure the prop would give first, but not sure here...prop
splines and hub look good.

2) Will I need to haul the upper off and check for damage? The only
thing I've done so far is peek under the upper housing cover, and the
gears/bearings are intact and looking good.

3) The other thing that I question is the engine coupler. Since the
engine did spin at 1500-2000 RPM that 5-10 seconds the first time we
noticed the problem, I want to make sure I didn't hurt it. Also, if the
answer to removing the upper is yes, I'll be closer to it. Can you
check it without running the engine?

Thanks for your help. Sorry for the wordiness, but wanted to give the
group a clear description. I have plenty of follow up questions
regarding its repair, but let's start here. Thanks for your help.

Claus Fasting