Gearbox problemo......HELP !

[bettyswollocks]

I changed the oil today and it was black !
After the new stuff was put in the box was actually worse so I pulled it out and rang the previous owner. He confirmed it was replaced about 4 months prior to me buying the boat, making it about 18 months old. Are these boxes crap or what ? Has anyone else had a bad experience with a ZF10M ?

I noticed in the manual they are only guaranteed for 12 months, or 2 years if supplied to a boat manufacturer. That really is a poor warrenty for something so simple.

[Rockter]

No, you should not have to slip the ship to change the gearbox., but 4" isn't much to play with.

Is this the gearbox?...

T. Norris Marine Equipment - Special Offers

Disconnect the final drive from the gearbox and push the prop shaft aft.

The gearbox should come away fairly easily and 4" should be enough.

That's not the most expensive of gearboxes, even for the UK.

[Rockter]

Something has gone wrong.
Gearboxes almost never fail if there is oil in them, and Hurth is a well-known box.

[bettyswollocks]

But what can go wrong, they are so simple. They just drive a prop. It makes no sense why a boat should go through 2 boxes in such a short time.

[rocinante33]

Bettys,

Your story has a familiar ring to it. I just bought and installed a new Hurth ZF10M. It cost over $1K. It is bolted to a Universal M25 engine in my boat. I did not have as much clearance as you do, with only 2 inches. I was able to do the job with the boat in the water, but it was a big PITA! I removed hoses from the aft engine, pulled the heat exchanger, then unbolted motor mounts and lifted the engine and trans to gain enough clearance to pull the trans and bellhousing. The trans and bellhousing are bolted together from inside on my engine. Thereare a lot of bolts on the bellhousing, including one from the opposite side of all the others. I kept the front of the engine on its' motor mount and did not have to disconnect hoses or wiring at the front. I lifted it with a 4x4 beam across my companionway , a piece of chain around it, then a come-along puller to provide the lifting force. After lifting I supported the engine on 2x4 blocks while I muscled the trans & bellhousing out, then back in.
When all done, re-align engine & propshaft, if necessary (mine was). I will test it all on Friday.

First, though, you may try flushing your trans with some diesel fuel.....run it at the dock, power up & shift it til warm, drain & replace with good Dexron II equivalent fluid. If you get lucky, that may help.

BTW, you know how to check the fluid in a ZF Hurth, right? Do not screw the dipstick in while checking the level. Use the correct fluid.

What can go wrong, internal clutches and the mechanism that presses the clutches together. See Nigel Calder's "Boatowner Mechanical & Electrical Repair Manual," 3rd Ed. It has a good explanation. My local library has it, or it is a good one to buy.

Good luck!