Newbie Q - old Johnson 40 problem
 

I am a boating newbie and the new owner of a 1970-something Johnson 40hp
outboard. I have had it out for maybe 8 hours so far without any problems.
The other day it started acting up. When I push the throttle forward, the
boat moves, but then the engine just rev's up and the boat doesn't go
anywhere. The closest comparison I can make is that it seems like a clutch
is slipping.

I'd like to repair the engine myself. Where should I start looking?

Thanks for any info,

Pyro Dave.

Newbie Q - old Johnson 40 problem
 

P. Dave...

The prop hub is slipping. The shear pin on that engine actually connects
the prop shaft to a separate shaft/steel hub which is pressed into a rubber
hub/bushing which is then pressed into the propeller housing. It all looks
like one piece as mounted on the engine, but when you take the plastic prop
nut off with the cotter pin, and then slide the shear pin out and prop off,
it will become obvious on the back side (fore facing) as to the
construction.

Get a new hub pressed in at a prop shop, and get a spare prop too.

Good Luck!

Rob
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"Booms" wrote in message
news:Rj27b.9866$J6.639@pd7tw3no...
I am a boating newbie and the new owner of a 1970-something Johnson 40hp
outboard. I have had it out for maybe 8 hours so far without any
problems.
The other day it started acting up. When I push the throttle forward, the
boat moves, but then the engine just rev's up and the boat doesn't go
anywhere. The closest comparison I can make is that it seems like a
clutch
is slipping.

I'd like to repair the engine myself. Where should I start looking?

Thanks for any info,

Pyro Dave.

Newbie Q - old Johnson 40 problem
 

It's possible the shift linkage is not fully engaging when you shift into
forward gear. Does your reverse work ok? If reverse works and forward does
not, it's the linkage. If both don't work, it could be the rubber spline on
the prop or still possibly linkage but less likely.

Newbie Q - old Johnson 40 problem
 

Reverse works. Forward works too, except when I increase the throttle. I
pulled the prop off and it is not splined. It has a pin that holds the prop
in position on the smooth shaft. There is no rubber hub, but there is what
looks like a bronze one. I don't think there is any way for the prop to
slip on the shaft, being that is held on by a steel pin through the whole
thing. Is there a shaft coupler that could possibly be broken?

Thanks.


"AKPBrown" wrote in message
...
It's possible the shift linkage is not fully engaging when you shift into
forward gear. Does your reverse work ok? If reverse works and forward
does
not, it's the linkage. If both don't work, it could be the rubber spline
on
the prop or still possibly linkage but less likely.

Newbie Q - old Johnson 40 problem
 

On Wed, 10 Sep 2003 15:51:47 GMT, "Booms"
wrote:

Reverse works. Forward works too, except when I increase the throttle. I
pulled the prop off and it is not splined. It has a pin that holds the prop
in position on the smooth shaft. There is no rubber hub, but there is what
looks like a bronze one. I don't think there is any way for the prop to
slip on the shaft, being that is held on by a steel pin through the whole
thing. Is there a shaft coupler that could possibly be broken?

Thanks.

It could be that the "dogs" on the forward gear are worn, and
dis-engage under load. If it's not the prop (remember, there is much
less load on a prop in reverse than at WOT) I would buy a manual and
drop and split the lower unit and inspect all gears.

Newbie Q - old Johnson 40 problem
 

On Fri, 12 Sep 2003 16:21:03 GMT, "Booms"
wrote:

"Joe Here" wrote in message
.. .
It could be that the "dogs" on the forward gear are worn, and
dis-engage under load. If it's not the prop (remember, there is much
less load on a prop in reverse than at WOT) I would buy a manual and
drop and split the lower unit and inspect all gears.

I have a manual that addresses Johnson engines from 1956 thru 70-something
and 1.5hp-40hp. I will have to give that a try. If only one side of the
dog is worn, is it possible to change the direction of the dog so that
reverse will slip, but forward will be ok?

I don't believe the gears can be swopped. Worn dogs can however be
built up if you know someone with a welder, milling machine & a
dividing head......tricky at best. E-bay is a better shot.

If it were my motor, instead of speculating, I would inspect the
inside first, or at the very least, drain the oil an look for metal in
the oil. This comes from personal experience with a Johnson 15 HP.

Smacked a rock a high speed (never lock the motor down, even when
reversing) motor kicked up and no apparent damage. Next oil change,
metal shavings mixed in the oil flowed out too! The thrust bearing
let go and the rollers got ground up. The main drive gear was toast,
although there were no signs of it, the motor ran perfectly. This
shows that there could something really wrong inside, and it was just
a matter of time before "bad stuff" happened!!!

After replacing main pinion gear, seals, bearings etc. She now runs
fine. A good friend was able to "dress" the dogs (square them off) to
avoid what could be your problem. There is a small detent ball that
holds the gears together, if the dogs develop a "chamfer", they'll
kick the motor into neutral

I think there is a tendancy to "ease" an outboard motor into gear, I
noticed my son doing this and corrected him. It should "clunk" into
gear to avoid grinding the dogs away. Based on the age of your motor,
there have probably been a Hundred different people at the helm, many
of them, like me, new to boating, and grinding the dogs.

If everything looks OK inside the lower unit, check (and pray) the the
splines on the drive shaft are good.

Remember, just be patient and logical when you split the lower end.

Hope this helps,

Newbie Q - old Johnson 40 problem
 

P. Dave...

READ YOUR MANUAL under the "propeller" section. I still stand by the prop
hub slipping. I know that engine and prop up and
down, left and right, in and out. There IS a rubber hub between the bronze
hub (which is rotated/driven by the pin) and the aluminum prop. Just try
another prop and you will see the immediate difference. Forward, or
reverse, will NOT slip... it is a God-awful "chunking" sound and very
obvious.

The gears however, can be switched on this engine... the forward gear has a
bronze
bushing which must be pressed out and switched to the reverse gear (now
forward) first. They are otherwise identical, but the results are usually
less than satisfactory. The clutch dog can be used both ways on the shaft
too, but they are case hardened, and much more than a minor "dressing" will
cause a failure. The gears and dog are available in the aftermarket.

Rob
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"Booms" wrote in message
news:Pnm8b.125$VS2.101@pd7tw1no...
"Joe Here" wrote in message
...
It could be that the "dogs" on the forward gear are worn, and
dis-engage under load. If it's not the prop (remember, there is much
less load on a prop in reverse than at WOT) I would buy a manual and
drop and split the lower unit and inspect all gears.

I have a manual that addresses Johnson engines from 1956 thru 70-something
and 1.5hp-40hp. I will have to give that a try. If only one side of the
dog is worn, is it possible to change the direction of the dog so that
reverse will slip, but forward will be ok?