Thank you.

Now let me explain the way I understand it: grin

No, it's not unique to your motor - most all of them do that.

Think of it just like a ratchet - it'll spin - but under drive it's an
absolute connect. If the ratchet pawls slipped under high load - your
ratchet needs to back to Sears. Now if the prop is somehow immobilazed
AS you put it into gear - then it may not engage - accompanied by a very
loud grinding noise as the thing tries to drop in but kinda "can't".

What really happens is the the one way "pawl action" of the prop allows the
propeller "in all cases" to spin forward faster than the motor is turning.
That menas when the motor is stopped you can turn it clockwise and it will
click click click. I assure you that if for some reason you were cruisong
along with the prop at 2000 rpm and "the hand of god" reached down with the
ability to turn it at 2004 rpm - it would still go click click click. In
other words the prop can always turn ahead. What this action does is allows
the prop to "free wheel" a bit when the boat is moving along at WOT and you
decide to chop the throttle. Try it and listen, you'll hear the prop
clicking away till the boat slows down. This protects the drivline from
"trying to turn the engine" - something it was not meant to do.

I assure you, that in a case where the engine is driving the prop (assuming
all is tight and correct)that the connection from the engine to the prop is
pretty much absolute and non-negotiable. What happens when something tries
to stop a prop under power is: A) the prop gets damaged. B) the driveline
gets damaged. OR C) The prop spins on it's rubber hub.

Trust me that I've seen props (aluminum and stainless steel) get torn up at
every RPM and boat speed imaginable.

NOw, in your case, I'd bet money that your prop has a rubber hub separating
the splined part that goes over the propshft, from the prop itself. This is
visible only from the rear of the prop as a general rule. So, what happened
is your prop "spun on the hub" when it was engaged with the rock, and later
with the rock removed it functioned normally again.

On a bigger motor, the prop may well need to get "re-hubbed" after such an
episode. In your case you got lucky and the low torque of your 25hp motor
was not sufficiant to exploit the (somewhat)weakened condition of your
pressed in prop to hub rubber bushing.

The ratchet was not in play saving your prop. If it was, you would have
heard a hell of a grinding noise - and not reved the motor at all out of
fear.

-W


"Paul Dougherty" wrote in message
om...
Sure, on my outboard if it is in forward, with the motor not running,
the prop will spin clockwise but not counter-clockwise. There is a one
way clutch in the gear box that causes this to happen. Now when the
motor is running in forward gear the gearbox will turn the propeller
to move the boat forward. But, if the prop hits something it will stop
turning but the motor and the gearbox are protected because the one
way clutch will allow them to spin freely.
My outboard is a 1985 25 hp Mariner so this might be unique to them. I
do not know. It also does not have a shear pin because the clutch will
allow everything to turn free.
I can tell you first hand that this work well because I had a rock
stuck between the prop blade and the cavitation plate the motor would
rev up and the boat would not go anywhere until I got that rock out.


Paul


"Clams Canino" wrote in message
news:HaDdb.613735$o%2.286517@sccrnsc02...
Can you explain *exactly* how this "protection" works?

-W

"Paul Dougherty" wrote in message
om...
Careful the prop is supposed to spin freely in one direction when the
selector is in forward. it protects the prop if you hit something.

Paul


(Brian Silver) wrote in message
. com...
Hi,

I am new to boating and screwed up my lower unit.
I think I stripped the gears because at one position the prop will
rotate
freely while in gear (forward).
I removed the 5 bolts below the anticavitation plate and the lower
unit
has dropped an inch but is being held by the shifting linkage rod.
Am I looking for trouble or can I remove the lower unit easily.
I think the shifting rod can be freed up from under the
carburator(s)
Would I then slide the whole rod out?
Would I mess up the shifting setup?
I have all winter to work on this and so far it has been
interesting,
Thanks for the responses in advance,

Brian Silver, Little Long Lake, Ontario, Canada.