0:00
The lower unit on any outboard is a key component to the boat because this item
0:08
is what converts the power from the engine to the prop shaft that spins the propeller, allowing
0:14
the boat to move through the water and take you from spot to spot. So what happens when this prop shaft breaks
0:28
Well, though this is a rare event, it does happen, and it is never a good time for anyone
0:33
And if you are lucky, you might be able to just change out the prop shaft and be back on the water without having to buy a new lower unit
0:42
Which is exactly what we will be doing today with this Yamaha 9.9 horsepower engine
0:49
I don't know how this happened, but the end of the prop shaft has been broken off right where the cotter pin goes through to hold the prop nut on
0:56
The first thing we need to do is get the propeller off of here and get the lower unit off
1:01
so that we can pull everything apart. The nice thing about these little lower units is that you don't need a lot of torque for the prop nuts
1:09
Just stick a piece of wood or some kind of a block in between the prop and the plate and
1:14
we can get the nut off and pull the propeller off the lower unit
1:21
Now we can really see how the end of the prop shaft has been broken. off
1:30
Pulling the lower unit off is also pretty easy on the little engines. We just need to get the four nuts off that go around the lower unit
1:40
And then in here you can see the shift shaft and how it connects to the shift shaft coming
1:44
from the engine. Most of these engines will have some sort of a nut or coupler system that connects the two
1:50
shift shafts together. Usually you have to unset the locking nut and then unscrew the coupler up or down onto one of the shift shafts
2:12
and then they will separate. Once the shift shaft is disconnected, we need to remove the locking nut from the lower unit shift shaft
2:24
and we can then pull the gearcase off of the engine, and once that's off, we can just carry the heavy little gear gear
2:31
the heavy little gear case over to a workbench. Where we can then stick it into a vise so that we can easily work on pulling out the old
2:45
broken prop shaft and installing the new one. Before doing anything else though, we will want to drain out all the gear loop that is in the
3:00
lower unit. Another nice thing about these little units is how easily we can move them
3:05
around and get out the vent and drain screws to drain out all the fluid
3:25
As we can see from the gear loop, it's just black and dirty so that is a good sign, meaning
3:30
that there isn't any kind of significant damage done on the inside of the lower unit
3:35
We have articles and videos that will be in the description in case you are curious about
3:40
what are all the different colors of gear loop that you will see when changing out your lower
3:44
unit oil and what these colors tell you about what's going on inside of your gear case
3:50
Once all the gear loop is drained out, we'll reinstall the drain plug. and stick the lower unit back into the vise
4:06
where all we need to do is loosen up these two 10 millimeter bolts from the carrier and then pull the bolts out With those out you might find especially when being used in salt water that the carrier is stuck in the gear case and is going to give us some trouble when trying to pull it out
4:23
So you might have to do a little hammering with a chisler punch and spray some oil on
4:27
the carrier to get it loose. Then we can pull the entire carrier and prop shaft out of the lower yule
4:39
unit and lay it on our rag where we can change out the broken prop shaft with the new one
4:44
There isn't much to these little cases, we just have to pull out the old shaft from the
4:48
bearing carrier and set the carrier to the side
5:00
Then we'll pull off the shim and pull out the shifting lobe that is in the front of the prop shaft
5:06
We can take a pick or something to get the spring off of the spring off. the clutch dog and push the pin out so that we can remove the clutch dog from the shaft
5:21
And get the shift lobe spring out of the old prop shaft. With all of these parts off
5:29
the old shaft we can open up the new prop shaft and begin the reassembly portion of this project
5:37
We just need to put the lobe spring. back in, reinstall the clutch dog, align so the pin will go back in
5:51
Once the pin is back in, we can reinstall the spring that keeps the pin in, keeping
5:56
the clutch dog in place, and then put the shift lobe in and slide the shim, and then put the shiflobe in, and slide the shim
6:09
back onto the other side of the prop shaft. We go ahead and clean up the barren carrier before putting it onto the prop shaft and then grease up
6:34
the O rings that are on the carrier. With everything greased up we can slide the prop shaft
6:40
assembly with the barring carrier back in the lower unit. and just reinstall the two 10 millimeter bolts that hold it on
6:57
Now for any of you that have seen our older video on rebuilding a lower unit, which was made
7:02
before we knew how to really edit a video, so it's pretty cringe-worthy in our opinion, but
7:08
you'll notice a huge difference in the complexity of rebuilding a larger horsepower lower unit
7:13
from doing this little 9.9 Yamaha gear case. There are a lot more tolerances and parts and pieces to be able to handle the torque
7:21
and stress that is put on a larger engine, so there is actually a huge difference between the larger gearcases and the little ones
7:29
Once the lower unit is back together though, we can reinstall it back onto the engine
7:34
As usual, we want to grease everything up and then slide the lower unit back up into the engine
7:39
where we can put the locking nut back on the lower unit shift shaft
7:43
Then we can shift the engine down to where we can put the shift coupler back on and tighten up all the bolts securing the lower unit
7:56
We'll want to make sure that the engine is shifting properly and that the lock nut is snug against the coupler
8:02
And we'll reinstall the propeller and ask you to make sure you've hit that like button for the good old YouTube algorithm and that you are subscribed to the channel
8:11
Also let us know about what kind of lower unit trouble you've had in the comments section below
8:16
Visit us at born againboating.com and check out some of these videos that you might have missed
8:22
We want to thank you for hanging out with us today and we look forward to seeing you next week
