Earlo
Well-known member
I have 1973 Johnson 20 hp that I thought I was having lower unit issues. When ever I opened the throttle beyond 1/2 it would rev really high and lose propulsion. When I would back off the throttle, it regain propulsion and run fine. I was convinced that it was the clutch dog and I opened the lower unit. The clutch dog alone retails for $142 & the forward gear retails for $327.
I was looking all over the country for parts, and I wrote a guy in Iowa with a parts request. He quoted the some prices that were better than the above, and the wrote:
What actually is going on when you run the motor? When you put the motor in gear & idling along then you go to rev it up or speed up, (going across the lake) Does the motor rev up, but you don't go anywhere & then you bring the throttle back to idle & then the motor automatically starts going forward again. This situation would probably be the hub slipping in the prop. But if you are at a higher rate of speed & rpm's & going along fine & you hear a bang or like you hit a log but you can keep going, then that would be jumping out of gear. Look at the prop face where the nut/cone goes on it & see if the paint is gone & the face looks like it has been ground into some. Which would be the prop shaft & nut spinning but not the actual face of the prop moving & that nut spinning against the face would wear into the prop. Then you definately have a slipping prop. Also look to see if the center brass hub in the prop seems to off set & not centered & that would probably mean it it slipping also.
I looked at the prop, and sure enough it was off center. There's a prop service shop nearby and they took one look at it and said it was a bad hub. They had a new prop in stock for it that was $115. I chose to do that rather than repress the hub into a 40 year old dinged prop.
I CANNOT SAY ENOUGH about the help I got from Dan Gano with gannotech.com. Rather than try to sell me something, he helped me figure out my misdiagnosis and hopefully get back on the water.
I was looking all over the country for parts, and I wrote a guy in Iowa with a parts request. He quoted the some prices that were better than the above, and the wrote:
What actually is going on when you run the motor? When you put the motor in gear & idling along then you go to rev it up or speed up, (going across the lake) Does the motor rev up, but you don't go anywhere & then you bring the throttle back to idle & then the motor automatically starts going forward again. This situation would probably be the hub slipping in the prop. But if you are at a higher rate of speed & rpm's & going along fine & you hear a bang or like you hit a log but you can keep going, then that would be jumping out of gear. Look at the prop face where the nut/cone goes on it & see if the paint is gone & the face looks like it has been ground into some. Which would be the prop shaft & nut spinning but not the actual face of the prop moving & that nut spinning against the face would wear into the prop. Then you definately have a slipping prop. Also look to see if the center brass hub in the prop seems to off set & not centered & that would probably mean it it slipping also.
I looked at the prop, and sure enough it was off center. There's a prop service shop nearby and they took one look at it and said it was a bad hub. They had a new prop in stock for it that was $115. I chose to do that rather than repress the hub into a 40 year old dinged prop.
I CANNOT SAY ENOUGH about the help I got from Dan Gano with gannotech.com. Rather than try to sell me something, he helped me figure out my misdiagnosis and hopefully get back on the water.
