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Johnson 50 (1996) increase revs without moving throttle

G

Gubi

New member
Hi,

I own a Johnson 50 outboard (1996) 2 stroke.
It starts without any problem. However, when I push the throttle to aprox, 3500 revs, the motor starts increasing revs (up to maximum revs in few seconds) without moving the throttle!

Can someone help me please?

Thanks
 
Gubi said:
Hi, I own a Johnson 50 outboard (1996) 2 stroke. It starts without any problem. However, when I push the throttle to aprox, 3500 revs, the motor starts increasing revs (up to maximum revs in few seconds) without moving the throttle! Can someone help me please? Thanks
Click to expand...

Is that engine in the water (launched) and in gear when this happens?

Is this engine new to you OR have you owned it for some time?

When was the last time it ran with no problems?

Have you or anyone else done any work on that engine since it ran okay last... and if so, what?
 
Thank you for your reply.

No the engine is in the garage. even when on gear (in the garage) increase in revs.

I've owned it for some time. At the first run was ok, then serviced by a mechanic (impeller and lubricated) he stated that the motor fuel intake was modified and he fixed it.

Another problem was with the stator motor and had to change it. According to the mechanic, this occurred since the main switch terminals were damaged.
 
That is called runaway and is caused mainly by revving it up in a no-load condition. Could also be caused by faulty link & sync, but your guy checked that (I assume). However you as much as admitted you are causing it yourself. Why in blazes are you revving it up to 3500 RPM out of the water?
 
Thanks for your reply

I am revving it up to 3500rpm out of water since this issue happened at sea.
The mechanic checked the link and sync and he told me that he have set them and I am checking the motor in the garage before trying the boat at sea.
 
Gubi said:
I am revving it up to 3500rpm out of water since this issue happened at sea.
Click to expand...

If you should have somehow opened up the throttle while in neutral.... at sea, you'll encounter this often.

What you are encountering in your garage is a runaway engine as Gator states. Eventually you'll encounter the scenario whereas the engine will diesel and by the time you figure out how to shut it down, connecting rods will be flying out the side of that crankcase. Don't do that!
 
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