Hurth gearbox - loss of drive in ahead but fine in astern

[GrahamW]

A friend of mine has a 1993 29HP Perkins Perama with a Hurth HBW100 gearbox.

On taking her out one day at the end of last season we noticed a marked drop in drive while going ahead. Revs were fine but there was not enough power to make more than a knot or two. However there was masses of power when going astern.

We have carefully checked the gear shift cable and the lever it connects to on the gearbox and can see no problem or difference between forward and astern modes.

The boat is still in the water but we have checked the prop ( 3 blade fixed ) and can see no problem there.

At the beginning of last season we did top up the fluid in the gearbox which appeared to be very low, i.e. there was no level showing on the dip stick when we checked it. The manual called for "ATF Type A" but we could not find that so used Castrol ATF Dex II. The engine and gearbox worked perfectly all summer until " out of the blue" the loss of drive in forward gear occurred - it did not occur while underway / in use - so far as we can tell it was fine when she was moored up at the end of one trip but then short of power at the start of the next.

Does anybody have any suggestions as to what the problem might be?

A few years ago the boat was being moved by a yard in Scotland and one of their engineers felt that the clutch was slipping. The yard drained the transmission fluid, replaced it with diesel and then ran the engine for a brief period, which apparently solved the slippage problem. Is that maybe worth a try?

Thanks for your help.

[GrahamW]

In my original post I should probably have made it clear that the yard in Scotland only ran the gearbox with diesel in for a short time, after which the transmission fluid was reinstalled/replaced.

[highseas]

Is that a 1993 transmission also?If so probably time for a replacement.Clutches are toast.Dextron 3 or synthetic ATF

[GrahamW]

Not sure about the age of the box. But do know that the whole set up has been lightly used throughout it's life.

[MarkSF]

They say most issues are with adjustment of the selector.

If you are sure that is not the issue, it's likely that a rebuild is in your future.

I think I would also look at the prop shaft, check that it's rotating slowly and it's not just the prop spinning on the shaft.

[highseas]

Once its used for some time not engaged in gear fully,damage is done.You can buy brand new HBW100 for $1200. One of my boxes did same,reverse, but no forward.Some use 10-30 motor oil instead of ATF.

[MarkSF]

You can buy re-conditioned ones, I don't think you can new Hurth boxes. You can replace with a (better) new ZF, but there are some installation complications.

[highseas]

Hurth is ZF.Check out Marine Parts Express.

[DeepFrz]

There are a number of threads on the HBW 100. Some have called it the $1.00 per hr. box. If it needs replacing check out Velvet Drive or PRM.

[Sailmonkey]

Originally Posted by MarkSF

You can buy re-conditioned ones, I don't think you can new Hurth boxes. You can replace with a (better) new ZF, but there are some installation complications.

The ZF10M is the hurth HBW 100. No install probs whatsoever. In fact the twin disc mg340 is also an almost exact drop in replacement.

[SailorHarry]

Sounds like your forward clutches are worn out. Also, ATF-A is Dexron III not II. Latest replacement for ATF-A is Dexron VI. The Dexron II maybe what caused the clutch failure, and if that is the case, look for a replacement transmission as your most cost effective solution if you have to pay someone to overhaul the transmission. You will have to be a very skilled mechanic to rebuild it yourself, and also have the necessary tools. Good Luck!

[Uncle Bob]

Originally Posted by GrahamW

A friend of mine has a 1993 29HP Perkins Perama with a Hurth HBW100 gearbox.

On taking her out one day at the end of last season we noticed a marked drop in drive while going ahead. Revs were fine but there was not enough power to make more than a knot or two. However there was masses of power when going astern.

We have carefully checked the gear shift cable and the lever it connects to on the gearbox and can see no problem or difference between forward and astern modes.

The boat is still in the water but we have checked the prop ( 3 blade fixed ) and can see no problem there.

At the beginning of last season we did top up the fluid in the gearbox which appeared to be very low, i.e. there was no level showing on the dip stick when we checked it. The manual called for "ATF Type A" but we could not find that so used Castrol ATF Dex II. The engine and gearbox worked perfectly all summer until " out of the blue" the loss of drive in forward gear occurred - it did not occur while underway / in use - so far as we can tell it was fine when she was moored up at the end of one trip but then short of power at the start of the next.

Does anybody have any suggestions as to what the problem might be?

A few years ago the boat was being moved by a yard in Scotland and one of their engineers felt that the clutch was slipping. The yard drained the transmission fluid, replaced it with diesel and then ran the engine for a brief period, which apparently solved the slippage problem. Is that maybe worth a try?

Thanks for your help.

Box needs to be rebuilt. Same thing happened to mine, cost of rebuild worked out slightly less than replacing with a new PRM, perfect drop in replacement.
Marine mechanic's advice was don't waste your money, engine supplier's advice was "we don't use that box anymore" so a new PRM it was.
Good luck.

[DeepFrz]

There was a thread on the forum about repairing the HBW/ZF 100 transmission. Also there were links to a blog with pictures and information on repairs. It seems that it was really a quite simple procedure and anyone that is handy with tool and has the patience could perform the necessary repairs. Unfortunately I don't remember the thread name or the blog but some google searches should be able to turn them up. Good luck.

[Jim Cate]

Originally Posted by SailorHarry

Sounds like your forward clutches are worn out. Also, ATF-A is Dexron III not II. Latest replacement for ATF-A is Dexron VI. The Dexron II maybe what caused the clutch failure, and if that is the case, look for a replacement transmission as your most cost effective solution if you have to pay someone to overhaul the transmission. You will have to be a very skilled mechanic to rebuild it yourself, and also have the necessary tools. Good Luck!

G'Day Harry,

Are you implying that Dexron VI is an improvement over D-III when used in a Hurth tranny? That is, should we be using it in ours?

Our HB100 failed shortly after we purchased this boat, replaced it with a ZF10 and have faithfully changed the Dexron III every 200 hours or less. Don't know what the PO used or how often it was done. We've now got around 3000 hours on the tranny and so far, so good. Would like to keep it that way, too!

Cheers,

Jim

[SailorHarry]

Hi, Jim, I can't say Dexron VI is an improvement over III ( it probably is), but if you have tried to buy any III lately ( in last couple of years) you may have a hard time finding any, as the latest spec is VI. The point of my message was that Dexron II and III aren't interchangeable and could have been the cause of failure. But it could have also been caused by partial engagement (allowing the clutch to slip and overheat) or just plain old wear.

Google Dexron III and VI and see for yourself. Don't take the word of any stranger on the internet.

Happy Sailing
Harry