I’m attempting to remove my transmission from my Kubota diesel and am not sure where the bolts are that attaches the trani to the motor, any suggestions? Anyone dealt with a Hurth?
HBW50 Hurth
- Thread starter Plymouth Sailor
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jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,174
Not sure about your unit.
If it looks anything like this the red arrows point to bolt holes. The bolts hold the transmission to the engine.
If it looks anything like this the red arrows point to bolt holes. The bolts hold the transmission to the engine.
My dad removed the transmission on our Universal (Kubota block) M12 years ago. I was a kid, but from what I've heard the back of the engine had to come off. I suspect the bolts for the transmission may be inside the bell housing?
Close up photos would be helpful.
On a Yanmar, the transmission is attached to a bell housing or adapter plate. The bell housing is attached to motor. Remove the bell housing and the transmission as a unit and then unbolt the transmission. In the photo below you can see some of the bolts that hold the transmission to the bell housing.
Here's the same unit with the transmission detached.
This is a ZF transmission made by Hurth. The transmission is bolted to an adapter plate with 6 bolt towards the center of the transmission. There are another 6 bolts connecting the adapter plate to a larger plate that attaches with 8 bolts (the outer most holes) The larger plate attaches to the engine. Bonus points to anyone who can identify the major mistake made in this assembly. The red cover is protecting the spline gear which engages with the crankshaft.
Same transmission from the aft end looking towards the engine. The bolts attaching the transmission are not visible.
On a Yanmar, the transmission is attached to a bell housing or adapter plate. The bell housing is attached to motor. Remove the bell housing and the transmission as a unit and then unbolt the transmission. In the photo below you can see some of the bolts that hold the transmission to the bell housing.
Here's the same unit with the transmission detached.
This is a ZF transmission made by Hurth. The transmission is bolted to an adapter plate with 6 bolt towards the center of the transmission. There are another 6 bolts connecting the adapter plate to a larger plate that attaches with 8 bolts (the outer most holes) The larger plate attaches to the engine. Bonus points to anyone who can identify the major mistake made in this assembly. The red cover is protecting the spline gear which engages with the crankshaft.
Same transmission from the aft end looking towards the engine. The bolts attaching the transmission are not visible.
Yes and no. The lever is in the traditional position which happened to be upside down for my application.
The actual orientation of the shift lever doesn't matter. The lever activates a cam within the body of the transmission, so that a clockwise rotation reverses the rotation of the engine so the boat moves forward with a RH prop (hence the name marine reverse gear), counter clockwise rotation engages the shaft in the same direction as the engine rotation. The cam is a basically an all or nothing engagement of the prop shaft. The orientation of the lever is dependent on the cable and the direction the cable attaches to the lever and the type of shift lever.
This all matters because the gear ratios when the transmission is reversing the engine rotation and not reversing it are different, in part to compensate for the inefficiency of a prop turning backwards (a RH prop turning L).
So why is all this necessary? When viewed from the front of the engine looking aft the crankshaft will appear to be turning clockwise or to the right. When viewed from the back it appears to be turning counter clockwise or to the left. For some unknown reason, tradition has it for props to turn clockwise when viewed from aft looking forward, the marine reverse gear (aka transmission) takes the counterclockwise turning and reverses it so that it turns clockwise.
Understanding reverse gears and shifting is, like marine electrical systems, one of the things that makes no sense until it does and then it becomes crystal clear and you wonder what the big deal was about.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,174
Bingo! I believe the bowl-like section of the back of the engine needs to be removed, thank you.
Yep, did mine last year. The bell housing has to come off. Then you can access the bolts holding the tranny to the bell housing from inside the bell housing. 
Here is the bell housing drawing for the M-25XP. As Ward said, you need to remove the bell housing because the bolts to the tranny are inside of it. It should be noted that the rear motor mounts are on the bell housing so you will need to lift the engine from the bed to remove the bellhousing.
