# I ain’t gotta clue lower unit? Linkage? Shift cables?



## Capt—matt (May 14, 2021)

alright boys help me out! So I got this 1980 70hp 2 stroke Johnson motor strong. First thing I tried 2 different props it’s not a spun hub. I take it out it’ll engage in forward reverse and neutral. Runs good before I try to jump out of hole and plain off, but once I start accelerating and try to come out the hole motor starts jumping and poppin away. Take it out of the water pit ears on it and it runs like a top in forward and reverse revd all the way up. I ran seafoam thru it drained the gas,replaced plugs, tried 2 different props thinking it was a spun hub still did it. So I pulled the lower unit off looked at the drive shaft and it has a couple cuts in it on the bottom end of the 4 spline, I engage the shift rod in neutral it spins freely, put the rod in forward and reverse hard to spin and sounds bad but turns pull the oil plug and got a good bit of metal on the magnet side of the plug and the recently changed foot oil is black and smells like gear oil. Do y’all think I have bad gears in the the lower unit and that’s what’s causing all this or do y’all think it’s something else I can’t find anything about it on any other forum or video. I just wanna try and make sure it is this before I go buy a lower unit.


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## topnative2 (Feb 22, 2009)

Capt—matt said:


> alright boys help me out! So I got this 1980 70hp 2 stroke Johnson motor strong. First thing I tried 2 different props it’s not a spun hub. I take it out it’ll engage in forward reverse and neutral. Runs good before I try to jump out of hole and plain off, but once I start accelerating and try to come out the hole motor starts jumping and poppin away. Take it out of the water pit ears on it and it runs like a top in forward and reverse revd all the way up. I ran seafoam thru it drained the gas,replaced plugs, tried 2 different props thinking it was a spun hub still did it. So I pulled the lower unit off looked at the drive shaft and it has a couple cuts in it on the bottom end of the 4 spline, I engage the shift rod in neutral it spins freely, put the rod in forward and reverse hard to spin and sounds bad but turns pull the oil plug and got a good bit of metal on the magnet side of the plug and the recently changed foot oil is black and smells like gear oil. Do y’all think I have bad gears in the the lower unit and that’s what’s causing all this or do y’all think it’s something else I can’t find anything about it on any other forum or video. I just wanna try and make sure it is this before I go buy a lower unit.


is the jumpin and popping in the top end as opposed to the gears?

If it is the lower unit, could be clutch dog

If it is in the top end, could be the a timing issue under the flywheel "magnets" could be getting loose after warm up


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## Capt—matt (May 14, 2021)

topnative2 said:


> is the jumpin and popping in the top end as opposed to the gears?
> 
> If it is the lower unit, could be clutch dog
> 
> If it is in the top end, could be the a timing issue under the flywheel "magnets" could be getting loose after warm up


If it was in the top in would do it when I have ut out of the water with ears on it right? As of right now it only does it under a load. I can let it run for 30 min in idle out of water with ears on put it in drive throttle up all the way and never does it but when I put it in the water and go to from idle to try and plain off it starts jumping and popping feel it all the way in the throttle box Makes the whole motor jump I have a video of I could figure out how to post thread on here.


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## topnative2 (Feb 22, 2009)

Capt—matt said:


> If it was in the top in would do it when I have ut out of the water with ears on it right? As of right now it only does it under a load. I can let it run for 30 min in idle out of water with ears on put it in drive throttle up all the way and never does it but when I put it in the water and go to from idle to try and plain off it starts jumping and popping feel it all the way in the throttle box Makes the whole motor jump I have a video of I could figure out how to post thread on here.


Ok....

Do one thing...run the motor in the dark like you just describe w/ the cowling off and look for fireworks....sparks jumping around from the plug wires etc.....we are trying to eliminate top end issues....

define popping?

if there are no sparks, I would say lower unit is the issue

does the motor go into gear smooth and crisp?


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## Capt—matt (May 14, 2021)

topnative2 said:


> Ok....
> 
> Do one thing...run the motor in the dark like you just describe w/ the cowling off and look for fireworks....sparks jumping around from the plug wires etc.....we are trying to eliminate top end issues....
> 
> ...


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## Capt—matt (May 14, 2021)

topnative2 said:


> Ok....
> 
> Do one thing...run the motor in the dark like you just describe w/ the cowling off and look for fireworks....sparks jumping around from the plug wires etc.....we are trying to eliminate top end issues....
> 
> ...


Yes goes into gear fine. Forward and reverse. When I say popping it’s more of like something is stopping the the prop from turning any faster and it’s feels as if a teeth on a gear somewhere is slipping when it does that. If you’ve ever messed with chains and sprockets it sounds and feels like a chain jumping on a sprocket because something is binding up


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## topnative2 (Feb 22, 2009)

spun hub is rolling around in my head except for the noise your describing.....just for grins.take the prop off and look at the hub from the motor side of the hub and see if it's messed up...if you have a spare prop try it..........money is on lower unit gears

all I got on it and will be off here for a few days...good luck w/ it


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## JC Designs (Apr 5, 2020)

Without seeing or inspecting, my first thought from your description alone is the clutch dog is worn and needs replaced. It will still engage but doesn’t have the bite to stay locked into the gears under load.


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## Capt—matt (May 14, 2021)

JC Designs said:


> Without seeing or inspecting, my first thought from your description alone is the clutch dog is worn and needs replaced. It will still engage but doesn’t have the bite to stay locked into the gears under load.


That’s what I’ve been thinking got someone that has a lower unit for sale been completely worked over and pressure tested for about $475 guess ima pick up a new one appreciate the input boys


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## m32825 (Jun 29, 2018)

Take the old one apart and tell us what you find. Inquiring minds want to know!


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## Capt—matt (May 14, 2021)

m32825 said:


> Take the old one apart and tell us what you find. Inquiring minds want to know!


I will for sure🤙


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