1970 Mercury 20 HP Problem
 

I have a 1970 20 HP Mercury. The engine is running fine, but the last
time we had it out something seemed to break between the engine and the
prop. The prop will turn when the engine is running slow, but when
trying to run faster the engine revs and the prop won't turn any
faster. (Like a clutch is slipping.)
Any suggestions? .............. Thanks, John...

wrote in message oups.com...
I have a 1970 20 HP Mercury. The engine is running fine, but the last
time we had it out something seemed to break between the engine and the
prop. The prop will turn when the engine is running slow, but when
trying to run faster the engine revs and the prop won't turn any
faster. (Like a clutch is slipping.)
Any suggestions? .............. Thanks, John...


Duh! You either sheared a pin or spun a hub. On a twenty-horse, I'd guess you spun a hub. Time for a new prop as it will probably
cost you as much to rehub as to buy new.

CN

On 8 May 2005 14:35:02 -0700, wrote:

I have a 1970 20 HP Mercury. The engine is running fine, but the last
time we had it out something seemed to break between the engine and the
prop. The prop will turn when the engine is running slow, but when
trying to run faster the engine revs and the prop won't turn any
faster. (Like a clutch is slipping.)
Any suggestions? .............. Thanks, John...

You spun the prop hub, thus you need a new prop.

You may be able to get the old prop rehubbed depending on condition.

Later,

Tom

Spun prop hub.......... take it to a prop shop or get a new prop.

-W

wrote in message
oups.com...
I have a 1970 20 HP Mercury. The engine is running fine, but the last
time we had it out something seemed to break between the engine and the
prop. The prop will turn when the engine is running slow, but when
trying to run faster the engine revs and the prop won't turn any
faster. (Like a clutch is slipping.)
Any suggestions? .............. Thanks, John...

Clams Canino wrote:
Spun prop hub.......... take it to a prop shop or get a new prop.

-W

wrote in message
oups.com...
I have a 1970 20 HP Mercury. The engine is running fine, but the
last
time we had it out something seemed to break between the engine and
the
prop. The prop will turn when the engine is running slow, but when
trying to run faster the engine revs and the prop won't turn any
faster. (Like a clutch is slipping.)
Any suggestions? .............. Thanks, John...


Thanks for the inputs, but, what is a "spun prop hub"? I pulled the
prop and the hub splines look ok...

The entire prop has three layers - the inner metal hub that is in
direct contact with the engine's prop shaft, the outer prop itself, and
a middle layer which is made of hard rubber, is bound tightly between
the two layers, and is designed to break free if the prop impacts a
solid object - to protect the inner gears and such.

"spun prop" means there is slippage between the rubber hub and the
other part(s). Bottom line is, in the water, the engine will turn the
prop shaft, but the prop itself slips due to the load of the water.
That's why it will be more obvious at higher rpms in the water as
opposed to idling or on the hose.

Specialized prop shops have equipment to install new rubber hubs. This
is worthwhile on larger expensive props. Your 20's prop is probably in
the vicinity of $75 or so, so it may or may not be worth while -
especially depending on the overall condition of the prop. If it's
dinged up, it's probably smart and cost effective just to buy a new
prop.

On 9 May 2005 14:53:27 -0700, "
wrote:


Clams Canino wrote:
Spun prop hub.......... take it to a prop shop or get a new prop.

-W

wrote in message
oups.com...
I have a 1970 20 HP Mercury. The engine is running fine, but the
last
time we had it out something seemed to break between the engine and
the
prop. The prop will turn when the engine is running slow, but when
trying to run faster the engine revs and the prop won't turn any
faster. (Like a clutch is slipping.)
Any suggestions? .............. Thanks, John...


Thanks for the inputs, but, what is a "spun prop hub"? I pulled the
prop and the hub splines look ok...

Think of a double threaded insert - that is essentially what a hub is.
The hub is spinning properly on the driveshaft - what is happening is
that it is spinning inside the prop hub. The connection to the
driveshaft is fine, the connection to the prop isn't.

Later,

Tom

Rubber bushing in the prop spins freely............. should not.

-W

wrote in message
oups.com...

Clams Canino wrote:
Spun prop hub.......... take it to a prop shop or get a new prop.

-W

wrote in message
oups.com...
I have a 1970 20 HP Mercury. The engine is running fine, but the
last
time we had it out something seemed to break between the engine and
the
prop. The prop will turn when the engine is running slow, but when
trying to run faster the engine revs and the prop won't turn any
faster. (Like a clutch is slipping.)
Any suggestions? .............. Thanks, John...


Thanks for the inputs, but, what is a "spun prop hub"? I pulled the
prop and the hub splines look ok...

Good explanation...In 50 years of owning outboard motors, I have never
had this happen to me. A local Mercury dealer quoted a price of $102.50
for a new prop and a prop shop here said they would re-hub mine for
about $40. The prop is in good shape otherwise..................Thanks
for the help everybody...........

On 8 May 2005 14:35:02 -0700, wrote:

I have a 1970 20 HP Mercury. The engine is running fine, but the last
time we had it out something seemed to break between the engine and the
prop. The prop will turn when the engine is running slow, but when
trying to run faster the engine revs and the prop won't turn any
faster. (Like a clutch is slipping.)
Any suggestions? .............. Thanks, John...

Sell it, and use the money to pave your driveway.