Question about prop hub slippage
 

Hi...I have a 1979 50hp Johnson SeaHorse, model # 50RL79C, on a 15'
Hourston runabout. It's been running strong lately, no problems at all. I
took it out yesterday afternoon, and suddenly it is churning the water and
not much else at WOT. Its moving as I would expect at low throttle, but when
I throttle up it doesn't go much faster. The bow of the boat porpoises
upwards, ands thats pretty much it. I'm figuring the bulk of the extra
thrust is coming just from the exhaust. I've tried a couple more times since
then, same result.

The motor is fine, shifting in/out of gear is fine. The only thing I can
think of is that the rubber is slipping in the prop hub. I tried having
someone hold the flywheel still while in gear, but I couldn't make the prop
slip on dry land. I don't see any signs of shredded rubber or anything
either, but I'm guessing I probably wouldn't anyhow. I know I can't put the
kind of torque on it that it probably gets in the water at WOT either. The
propeller is older, and was going to be replaced this season, so...

Does this sound familiar to anyone? Am I correct in thinking its the hub
slipping? I cannot see any kind of a clutch in the exploded diagram of the
leg, so I'm thinking thats the only possible place for slipping.

p.s. None of the weights in the boat have not changed, nor has their
location. The bilge is bone dry, nothing is dragging, and the motor is
indeed aligned correctly with the keel. No rocker or hook in the keel
either.

Any tips or advice would be greatly appreciated, thanks!

Question about prop hub slippage
 

"Paul Browne" wrote
Does this sound familiar to anyone?

Sounds a lot like what happened to my merc prop last year. Nothing visible,
and it worked at very low speed, but above that speed it was like popping
the car out of gear. As I recall, I paid around $50-60 to have the hub
rebuilt.

Question about prop hub slippage
 

weird..
I had the same symptom happen to me... once I reached more than a few knots,
the engine would start to rev, like we /should/ be crusing right along, but
we were dead in the water.. we could cut the throttle, and then power up
again, and the same thing would happen.. we could stay underway if we didn't
go more than a few knots..
just like a transmission slipping out of gear... only *my* issue went away
on it's own.... very odd..

-j


"Joe Blizzard" wrote in message
...
"Paul Browne" wrote
Does this sound familiar to anyone?

Sounds a lot like what happened to my merc prop last year. Nothing
visible,
and it worked at very low speed, but above that speed it was like popping
the car out of gear. As I recall, I paid around $50-60 to have the hub
rebuilt.

Question about prop hub slippage
 

I had this problem. Solved it by having the correct transmission fluid
level in the Hurth transmission.


"Jay" wrote in message
...
weird..
I had the same symptom happen to me... once I reached more than a few
knots,
the engine would start to rev, like we /should/ be crusing right along,
but
we were dead in the water.. we could cut the throttle, and then power up
again, and the same thing would happen.. we could stay underway if we
didn't
go more than a few knots..
just like a transmission slipping out of gear... only *my* issue went away
on it's own.... very odd..

-j


"Joe Blizzard" wrote in message
...
"Paul Browne" wrote
Does this sound familiar to anyone?

Sounds a lot like what happened to my merc prop last year. Nothing
visible,
and it worked at very low speed, but above that speed it was like
popping
the car out of gear. As I recall, I paid around $50-60 to have the hub
rebuilt.

Question about prop hub slippage
 

Also Sprach Paul Browne :

The motor is fine, shifting in/out of gear is fine. The only thing I can
think of is that the rubber is slipping in the prop hub. I tried having
someone hold the flywheel still while in gear, but I couldn't make the prop
slip on dry land. I don't see any signs of shredded rubber or anything
either, but I'm guessing I probably wouldn't anyhow. I know I can't put the
kind of torque on it that it probably gets in the water at WOT either. The
propeller is older, and was going to be replaced this season, so...

Take a marker or a bit of paint and make corresponding marks on the inner
and outer parts of the prop hub. Take the boat out for a run. If the
prop is slipping, they will not be aligned anymore. From your
description, it does sound like it is slipping.

Dan


--
Ah... memories, memories. Where is that brain damage they promised us?

-- Hunter S. Thompson.

Question about prop hub slippage
 

"Paul Browne" wrote in message
news:Myrsc.9562$gx1.1484@clgrps12...

Does this sound familiar to anyone? Am I correct in thinking its the hub
slipping? I cannot see any kind of a clutch in the exploded diagram of the
leg, so I'm thinking thats the only possible place for slipping.


Yep. I have spun a couple of hubs, and each time it matched these symptoms
exactly. I could idle back to the launch ramp but couldn't get it to hold
above a fast idle.

Rod

Question about prop hub slippage
 

This leaves me still puzzled as to why my problem fixed itself...

-j


"Rod McInnis" wrote in message
...

"Paul Browne" wrote in message
news:Myrsc.9562$gx1.1484@clgrps12...

Does this sound familiar to anyone? Am I correct in thinking its the hub
slipping? I cannot see any kind of a clutch in the exploded diagram of
the
leg, so I'm thinking thats the only possible place for slipping.


Yep. I have spun a couple of hubs, and each time it matched these
symptoms
exactly. I could idle back to the launch ramp but couldn't get it to hold
above a fast idle.

Rod

Question about prop hub slippage
 

Thank you very much to all who replied, I'm feeling a lot more at ease now.
=) Had a small craft warning today, so I couldn't test the idea about
marking the inner/outer hubs. Hopefully be able to do that tomorrow and
confirm.