X-115 GT-115 gear case guts

**Mark75H** · 08-08-2011

I don't understand what you are trying to adjust

**Powerabout** · 08-08-2011

so how did they set them up?
Just raise lower pinions, run and check contact patch except you still need to do the set the timing gears or the 2nd shaft will do nothing and the first will force the driven gear into it?
Any other twin box you lock the propshaft and hence hold the driven gear(S) to do your timing gear backlash.

Saying that I have never worked on any OMC twin boxes only Merc

**Mark75H** · 08-09-2011

Whichever gear leads forces the driven gear to the second gear. All the set up has to do is not bind and be close. All the gears and splines are straight, there is no critical timing like a Super Speedmaster

**NERSTROM** · 08-09-2011

Most, if not all, of the OMC V4 and early V6 twin pinion gearcases were built by Ward Cox who was a member of the race team. The pinion gear vertical location was shimmed based on the distance from the propshaft centerline to the upper bearing carrier. The transfer gears, at the top of the driveshafts, were used to split the load equally between the pinions and into the floating bull gear on the propshaft. Transfer gear lash would be checked with the propshaft held solid and a load on the driveshaft. The transfer gears were then rotated until lash was 0.001" or less. Each transfer gear rode on a different spline which made this possible. If the transfer gears were not properly positioned the pinions would get uneven loads resulting in early failure. Ward built so many of these he was able to do all of this by feel. All OMC racing gearcases used this basic design, GT, 1:1, CC, CCC etc.

**brichter** · 08-09-2011

Jim, you mean the lash is checked with the shafts loaded vertically away from the propshaft, correct?
That way the pinions are against the thrust bearings which is the natural position when the unit is under load.
I made a tool out of a couple of valve springs and set screw collars for the purpose.

You can really tell when one of these units are not set up right, they will feel rough when you turn them almost like the gears are shot, then you pull the case apart and the gears look fine if not run too long that way.

I have 14 V4 race lowers that I have been tinkering with and still trying to get all the details.

**Powerabout** · 08-09-2011

how many different twin pinion boxes were made?
V8 (F1 and offshore)
SST100?
CCC
CC
X115
or did they make new ones each time a new engine came out?

Thanks

**Dave S.** · 08-11-2011

The back shaft has flats that you can hold to set the lash.....Who called me Krazzy......Ya be lucky to drop the top gears in place.... then try again and set them so the load is even...... SSM is harder as the top gears are hypoid,,,,, Nice pixs