X-115 GT-115 gear case guts

[Mark75H]

Crazy Dave (who owns a highly profitable tick farm somewhere in the south) has been at it again ... he always wants to know what is inside things so he took this apart and figured out how it works.


DO NOT COPY PICTURES OR TEXT FROM THIS THREAD TO ANY OTHER WEBSITES

[Mark75H]

The double sided prop shaft gear that the red arrow points to has splines inside it and can slide front and back on the tube it is mounted on. That's right, its on a hollow tube, not directly on the shaft with the prop. The green arrows point to the tube. The prop shaft passes all the way thru it and is located and supported at the front by the tapered roller bearing.

[Mark75H]

Now the reverse gear gets some arrows. It is always engaged to the back of the rear driveshaft gear. It is mounted on a bearing spinning on the tube ... a tube outside of a tube, so it does not cause the tube with the double sided gear to turn ... in fact, it turns the opposite direction of the tube, because its on the other side of that back gear.

[Mark75H]

Next we revisit the first hollow tube that the double sided gear runs on. All 4 arrows point to different sections of one piece of metal ... the very long arrow points to "dogs" on it that will engage the shifter sleeve in a couple more posts

[Lars Strom]

Hmm..interesting..I did not know how a two pinion gearcase with reverse worked..and I raced that gear case 1973.. the Evinrude 65SS used the old X-115 lower unit.

Thank you..now I can sleep good..

[wolfgang]

Thank you for the lecture, Sam. I have never seen the inside of one of these, nor seen any catastrophic failure. Great OMC engineering! rgds.

[Mark75H]

2 views of the shift slider that engages one set of shaft dogs or the other.

That this shift slider is hollow and cup shaped is very important, as you will see later.

It has internal splines that are always engaged to the actual center solid prop shaft and always turns with it. As we see it here the prop would be to the far left and the rear bearing and seal areas are visible


In the bottom picture, Dave is holding on to the slider; with it pulled farther forward than it naturally goes ... just so we can see the splines on the prop shaft while they are engaged to the slider.

[Mark75H]

The hole in the prop shaft spline area is where a spring loaded ball goes to provide a neutral detent position. You can see the corresponding space inside the slider where there is a gap in the internal splines.

[Mark75H]

Now we will put the shifter slider on the prop shaft in position to run the boat forward.

The pink arrow is pointing to the splines on the prop shaft where they are slightly visible.

The white arrows point to the tangs or "dogs" that engage to some other dogs for the actual shifting.

The slider is moved all the way to our left, in its closest to the prop position, that's why we can see a little bit of the prop shaft splines down in the cup where the pink arrow is pointing. You can also see the empty space behind the bottom dog inside the cup.

This is the solid prop shaft at the center of everything; the area at the right will slide into the hollow shaft where the gears are.

[Mark75H]

Now we'll look at the hollow shaft again. Here is the end with the dogs for forward, all the way at the left side of the shaft where the black arrows are pointing. Pink arrow points to the hollow center of this shaft, that's where the solid center prop shaft goes .