X-115 GT-115 gear case guts

[Mark75H]

The reverse gear and its outer support bearing ... and the dogs made onto the back of the gear. The reverse gear is not attached to the outer bearing or the hollow tube inside the reverse gear, it floats in both.

[Mark75H]

Here are the positions of the dogs on the shifter slider cup for each shift function.


When the cup is in the middle position being held by the detent spring ... the dogs inside the cup touch neither of the other shift dogs.


When the cup is pulled back, its dogs engage to the dogs on the hollow shaft and the main double sided gear transmits power.

When the cup is full forward, its dogs engage the dogs on the back of the reverse gear ... in that case, power comes down the back double shaft to the back gear and power transmits off the back of the rear gear to the reverse gear.

[Mark75H]

The double sided gear, the reverse gear and the pinion gears are always turning. The reverse gear is always turning opposite to the hollow shaft.

[Mark75H]

Recap:


Forward: Power comes down from the motor and splits to the 2 driveshafts just below the water pump. From each driveshaft power goes to a pinion gear driving the floating double sided gear mounted on the hollow shaft. Power automatically positions the double sided gear so 50% goes thru each gear. Power transmits along the hollow tube, thru the slightly larger hollow reverse gear to the dogs at the back of the hollow shaft. The shifter slider cup is at the full back position and the cup is engaged to the dogs at the back of the hollow shaft. Power transmits from the slider to the solid center main prop shaft. The solid main prop shaft and the hollow tube are turing together.

Reverse: Power comes down from the motor, transmits to the rear lower driveshaft, to its pinion gear and off the back of that rear pinion gear to the reverse gear. Then off the dogs made onto the reverse gear - to the dogs on the shifter cup (which is now in its full forward position). Again, from the shifter cup to the solid center prop shaft. Now the hollow shaft is not connected to the prop shaft and they are turning opposite directions, one inside the other.


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[Lars Strom]

My gear case from 1973..

[brichter]

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.

These are good units for racing but shift parts aren't great as you can clearly see from these pictures. I don't recommend using them for fishing or skiing.
My dad and other guys that raced these always locked them in forward which was allowed after maybe 71 or 72.

I heard from one of the OMC race team guys that this unit was a joint venture project of Charlie Strang and Doc Jones.

[Lars Strom]

..not very good for shifting..but a very strong gear case..
Over in Sweden we took the Super Strangler V-4 without shifting..
put this gearcase on instead..installed the shift level on the mid section and raced local offshore racing..The role said..must have neutral/reverse..

Yes..this is the latest strongest ON V-4 race engine OMC raced before going V-6..

[Powerabout]

I wonder how the shimming was done?
OK pinion height by tool and feeler gauge but how do you set the back lash let alone the load per shaft, just with the timing gears?
How do you hold the double gear still?

[Mark75H]

The double gear is not held still, it slides on the shaft and self centers, automatically equalizing the load on each input gear and shaft.

[Powerabout]

Sam
thats my point, maybe lock the prop shaft load up main drive shaft and set the 2nd timing gear to a known backlash?