"Jim" wrote in message
ink.net...

"Claus" wrote in message
...
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

A couple other things that haven't been mentioned yet. Since you have the
lower off and it doesn't seem to be going into gear when you move the
shift shaft into Forward, the shift crank could be bent or worn, or
broken, or the shift spool could be worn or the spring fatigued. With
rounded cogs on the gears and or sliding clutch, you might experience the
drive popping into or out of gear. I can't imagine anything wearing to the
point of causing shift failure without you noticing the shift quality
gradually deteriorating.

Make sure you are turning the vertical drive shaft clockwise. Turn the
shift shaft clockwise to lock into forward gear. Alternatively you could
turn the propshaft counter clockwise as you shift into forward and watch
for the driveshaft to rotate.

There should be a maximum of 12 degrees play in the shift shaft while the
sliding clutch is held under tension by the forward gear. 6 degrees would
be ideal.

Another thing that could happen is that vertical shaft is made of two
different metels spun welded together. The shaft could have snapped at the
weld or at the very top where the o-ring goes.

I'd suggest you have a shop look at it. They could probably tell you what
is wrong without even taking it apart.

Good luck,
Jim

Check the lower shift cable as well. It can work in one direction even if
broken. The shift dog in the lower gear case will leave metal in the oil
most all the time, but lots if "gone".
Not as good a system as the Volvo clone "cone clutch" in the Bravo series.

Good luck! Dan