YAMAHA 8hp 2 stroke shift rod problem

[Sharkbait Steve]

Hello, Just changed the impeller. Apparently the shift rod slipped out of engagement in the foot of the motor. It moves freely with about 2 1/2" of up and down travel. When I turn the prop, the drive shaft rotates no matter what position the shift rod is in. It's definitely not going into neutral. My question is: How to "reengage" the shift rod???

 

[QBhoy]

You’ll need to take the gearbox off again, by the sounds of it. Or at least make sure the selector assembly is in properly at the linkage down the mid section of the engine. You usually have to loosen that off before you take the gearbox off anyway. You must have disconnected that to get the box off for the impeller surely ?

 

[Martin_J]

We assume you only dropped the lower gearbox assembly away from the leg to get access to the water pump.

Did you however take off the prop and remove the cover located behind the prop to see if the impeller was there first? If so you could have lifted the prop shaft out slightly and dislodged the connection to the gear linkage.

 

[VicS]

Hello, Just changed the impeller. Apparently the shift rod slipped out of engagement in the foot of the motor. It moves freely with about 2 1/2" of up and down travel. When I turn the prop, the drive shaft rotates no matter what position the shift rod is in. It's definitely not going into neutral. My question is: How to "reengage" the shift rod???

It sounds as though you have not re-connected the upper and lower shift rods together properly .
You do not give any detail or state the age but I believe newer models have a screwed connector while older models have a clamp.

.

 

[VicS]

,

 

[Martin_J]

I was also making the assumption that the shift rod was moving up and down a couple of inches (and that the prop was continuously rotating the drive shaft) prior to even putting the lower gearbox assembly back onto the outboard leg.

 

[VicS]

I was also making the assumption that the shift rod was moving up and down a couple of inches (and that the prop was continuously rotating the drive shaft) prior to even putting the lower gearbox assembly back onto the outboard leg.

Difficult to understand what is happening if that's the case.
The shift rod terminates in a cam which bears against a plunger in the en d of the prop shaft which pushes the clutch from engagement with the forward gear through the neutral position and into engagement with the reverse gear against a spring.. as the shift rod is pushed down
Perhaps he is not pushing the shift rod and cam down hard enough and far enough to move the clutch dog. It'll need a good shove.
Gear case assembly

 

[Martin_J]

I only asked about the partial removal of the prop shaft because if you pull it part way out, then push it back into place again, the spring #50 in the diagram can push the plunger #51 out of its hollow in the end of the shaft #52.

With a plunger rattling around in the gear casing oil, the shift rod fails to do what it's supposed to do.

 

[VicS]

I only asked about the partial removal of the prop shaft because if you pull it part way out, then push it back into place again, the spring #50 in the diagram can push the plunger #51 out of its hollow in the end of the shaft #52.

With a plunger rattling around in the gear casing oil, the shift rod fails to do what it's supposed to do.

The spring won't push the plunger out because it's the other side of pin # 48 but the plunger might fall out if the shaft is withdrawn far enough

 

[Sharkbait Steve]

It sounds as though you have not re-connected the upper and lower shift rods together properly .
You do not give any detail or state the age but I believe newer models have a screwed connector while older models have a clamp.

.

,

Thanks for the suggestions everyone. We removed the prop and bearing carrier to engage the shift linkage with the plunger in the end of the prop shaft in it's proper position. It was a stroke of good luck that we had this problem as we discovered the gearbox was full of water instead of gear oil. Replaced the prop shaft seals, "o"-rings and bearing in the bearing carrier. Need to make a test run but I feel confident that it will be okay. I would like to have replaced the bearing on the front end of the prop shaft but not sure how to get it out. Looks like it would require the removal of the gears. Maybe a big job? I know I should "bite the bullet" and do it as the other bearing was in pretty bad shape. Any suggestions???

 

[QBhoy]

Thanks for the suggestions everyone. We removed the prop and bearing carrier to engage the shift linkage with the plunger in the end of the prop shaft in it's proper position. It was a stroke of good luck that we had this problem as we discovered the gearbox was full of water instead of gear oil. Replaced the prop shaft seals, "o"-rings and bearing in the bearing carrier. Need to make a test run but I feel confident that it will be okay. I would like to have replaced the bearing on the front end of the prop shaft but not sure how to get it out. Looks like it would require the removal of the gears. Maybe a big job? I know I should "bite the bullet" and do it as the other bearing was in pretty bad shape. Any suggestions???

Hate to ruin your thoughts around resolving the issue. But oil, water or even nothing in the gearbox at all…quite sure that wouldn’t result in the issue you first reported. Best of luck though.