'71 model Johnson 20hp outboard jumping out of forward gear momentarily
 

Wondering if anyone can make some suggestions of where to start
looking. My 71 20hp johnson sometimes momentarily jumps out of gear...
usually it does it for literally a second and it almost feels like the
boat has hit something in the water but it always keeps moving and has
never caused a significant problem. It only ever happens as the boat is
building speed, when under high load, once the boat is up on the plane
then it never happens. Today, however, it did it again, but it didn't
go back into gear until i reduced throttle, put it in neutral and then
back into forward gear again. After that it was ok again.

Each time it happens the gear lever on the side of the engine does not
move at all so it is something internal. Obviously ther is something
slipping, etc. I have rebuilt many car and motorbike engines, however
this is my first boat and i don't know the internals on this engine
yet. Could anyone advise me on where to start looking before i pull it
apart. Are there any common problems with the engine?

Thanks Dave.

'71 model Johnson 20hp outboard jumping out of forward gear momentarily
 

On 10 Jan 2007 04:31:35 -0800, wrote:

Wondering if anyone can make some suggestions of where to start
looking. My 71 20hp johnson sometimes momentarily jumps out of gear...
usually it does it for literally a second and it almost feels like the
boat has hit something in the water but it always keeps moving and has
never caused a significant problem. It only ever happens as the boat is
building speed, when under high load, once the boat is up on the plane
then it never happens. Today, however, it did it again, but it didn't
go back into gear until i reduced throttle, put it in neutral and then
back into forward gear again. After that it was ok again.

Each time it happens the gear lever on the side of the engine does not
move at all so it is something internal. Obviously ther is something
slipping, etc. I have rebuilt many car and motorbike engines, however
this is my first boat and i don't know the internals on this engine
yet. Could anyone advise me on where to start looking before i pull it
apart. Are there any common problems with the engine?

Thanks Dave.

Dave, I can't help you. You may have to wait a day or so, but there *are*
some knowledgeable folks here who will give you advice. Hang in there.
--
******************************************
***** Have a super day! *****
******************************************

John H

'71 model Johnson 20hp outboard jumping out of forward gear momentarily
 

wrote:
Wondering if anyone can make some suggestions of where to start
looking. My 71 20hp johnson sometimes momentarily jumps out of gear...
usually it does it for literally a second and it almost feels like the
boat has hit something in the water but it always keeps moving and has
never caused a significant problem. It only ever happens as the boat is
building speed, when under high load, once the boat is up on the plane
then it never happens. Today, however, it did it again, but it didn't
go back into gear until i reduced throttle, put it in neutral and then
back into forward gear again. After that it was ok again.

Each time it happens the gear lever on the side of the engine does not
move at all so it is something internal. Obviously ther is something
slipping, etc. I have rebuilt many car and motorbike engines, however
this is my first boat and i don't know the internals on this engine
yet. Could anyone advise me on where to start looking before i pull it
apart. Are there any common problems with the engine?

Thanks Dave.

Sounds like the rubber hub for the prop is spun. They get worn out.

'71 model Johnson 20hp outboard jumping out of forward gear momentarily
 

Short Wave Sportfishing wrote:

You might also have a worn holes in the shift rod which is not fully
seating the gears. You might have a worn drive shaft, but that's
unlikely - a possibility though.

Agreed on the wear. Like the possibility of the hole being elongated
from where the cable fits into the shift lever, ether the hole is
elongated, or the cable coupler is worn.

Possible cable stretch? worth thrust on the forward gear, or shifting
fork worn internally, where there's too much lash and gears are barely
catching each other?

'71 model Johnson 20hp outboard jumping out of forward gear momentarily
 

wrote:
Wondering if anyone can make some suggestions of where to start
looking. My 71 20hp johnson sometimes momentarily jumps out of gear...
usually it does it for literally a second and it almost feels like the
boat has hit something in the water but it always keeps moving and has
never caused a significant problem. It only ever happens as the boat is
building speed, when under high load, once the boat is up on the plane
then it never happens. Today, however, it did it again, but it didn't
go back into gear until i reduced throttle, put it in neutral and then
back into forward gear again. After that it was ok again.

Each time it happens the gear lever on the side of the engine does not
move at all so it is something internal. Obviously ther is something
slipping, etc. I have rebuilt many car and motorbike engines, however
this is my first boat and i don't know the internals on this engine
yet. Could anyone advise me on where to start looking before i pull it
apart. Are there any common problems with the engine?

Thanks Dave.

Is that the all manual shift version?
If so it is likely the clutch dogs wearing out. You could try adjusting
the shifter to get a little more bite in forward gear. But that does
make it more likely that you will start to have problems with reverse
at some point in the future.

'71 model Johnson 20hp outboard jumping out of forward gear momentarily
 

david wrote:
before i pull it apart.

"basskisser" wrote:
Sounds like the rubber hub for the prop is spun. They get worn out.

I vote to check this first.
Just borrow a prop. Or buy a used one for a spare and run it. It might
not be the problem but, if you're serious about the "before I pull it
apart" part, eliminate this possibility first.

Rick

'71 model Johnson 20hp outboard jumping out of forward gear momentarily
 

wrote in message
...
david wrote:
before i pull it apart.

"basskisser" wrote:
Sounds like the rubber hub for the prop is spun. They get worn out.

I vote to check this first.
Just borrow a prop. Or buy a used one for a spare and run it. It might
not be the problem but, if you're serious about the "before I pull it
apart" part, eliminate this possibility first.

Rick

Easiest way to check the hub, is take a Sharpie and mark the inner and out
with a line. Run the prop and see if the lines still line up.

'71 model Johnson 20hp outboard jumping out of forward gear momentarily
 

Thanks for the suggestions so far... havent had any time to look at it
since first posting but i will try to follow some of the advice later
this week. Think i will start with the prop, as its the simplest thing,
then look at the adjustment of the gear lever (the cable which actuates
the lever is fine, and the hole it goes into on the lever is not
elongated at all), then look internally if that doesn't produce
results. Ive got a feeling that its either the dog clutch or the gears
not meshing fully... just by the way it suddenly jumps in and out, it
is quite a sudden, harsh action... although ill look at the propr first
i would imagine that this would be a much softer action if it was
slipping then re-gripping on the rubber boot.

Keep the advice coming and ill post any developments when they
happen...

Thanks Dave.