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Johnson 1986 70VRO idle porblem

J

juhpel

New member
Hey everyone!

So, Im having this idle problem with my Johnson 70hp with a VRO pump.

Symptoms:

It only starts by using the choke (pressing down while turning the key to start). Even when warm, it needs the choke.
It won't idle in or out of gear. When not in gear, it will idle for 10 to 30 seconds and then die.
It will only idle for a couple of seconds when in gear.
The throttle works great, and it has good torque. Acceleration is very fast, and it runs great with more throttle.
I just put the boat on its trailer for a better look at the problem. When tested on the trailer using muffs, it idles great and does not die. This will, unfortunately, make my repair a lot harder.

Recent services I've done before the symptoms appeared include a VRO pump diaphragm check and replacing all the fuel lines for the VRO pump and choke pump.

I've now replaced all three spark plugs, but it did not have any effect.

I've only had this boat under year, that's why I did the preventive maintenance for the vro pump.
Thanks in advance!
 
The choke is NOT a pump.-----Trouble shooting on a 38 year old motor starts with a compression test,----Post the actual values here.
 
I did the compression test just now and everything seems to be in good condition by the manual.


9,5bars with very little variation.
 

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Reeds haven't been checked yet. Do you think they could cause this kind of problem?

I bought it very late in the summer and used premix fuel because the VRO wasn't checked. I bought it from a woman whose husband passed away, so she did not know anything about the boat or the motor.

I only rode it very little last season because of this. When I opened the VRO pump, it was clear that it's in excellent condition, so I only replaced all the fuel lines for it.
 
I do not own a rpm gauge. I need to dig in deeper for that. But idle speed in gear when submerged in water is very very low.
I mean that it will die very soon.

"How did it run for you last season ?----": it ran much better :). acceleration and max speed is pretty much identical exept idling
 
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