prop help needed

[RooSmith]

i have an early 70's 20hp johnson when runs great at idle but when i give it gas i get lots of vibration and starts to run rough revving and then slowing over and over, will not go fast or try to get on a plane, and i was told it could be prop issues, it appears to be slightly damaged, tips of blades bend in slightly, i was also told my prop hub could be slipping by someone, does this sound like what it could be......... it is on a 14ft malibu boat, and i recently had the carb cleaned,and foot oil replaced.

 

[steelespike]

Re: prop help needed

When a prop hub slips it is pretty much total.Once it slips it continues till you slow
and find the reduced power that allows movement before it slips.Surging sounds like a fuel delivery problem.Rough as you advance the throttle could be a link and sync problem.Timing advancing without the carb opening.The prop isn't likely to cause more than some light vibration and a slight reduction in performance based on your description.

 

[RooSmith]

Re: prop help needed

what do you mean by a link and sync problem? fuel problem was my first thought thats why i had the carb cleaned

thank you for your help and time

 

[bigrockets]

Re: prop help needed

link and sync is the term for synchronyzing the throttle linkage with the ignition timing linkage so that when the throttle control is moved from neutral to forward the ignition timing is in sync with the throttle linkage to make the motor accellerate smoothly. Its a routing maintenance proceedure that is in the service manual. It is also outlined in Johnson/Evinrude forum. Go to the Johnson/Evinrude forum and at the top of the forum you should find the information in the secret file or a stick at the beginning of the forum. I think you have an ignition or fuel delivery problem and not a prop issue. You might post the symptom on the J/E forum. That being said some damage to the prop will make it vibrate, bent blades will make it vibrate and a bent drive shaft will make it vibrate. You are not describing a vibration problem but are describing a performance problem. So if you put the symptoms on the J/E forum you will get lots of good advice but first read the "secret file" at the top of the forum and you may find the answers quickly.