Hurth Gearbox problem...

[dickh]

I have a Hurth HBW 50 gearbox mated to a Perkins Perama M20 engine(18HP).
Reverse gear works fine, but in forward the gearbox engages OK at idle speed but when revved up the propshaft stays at idling speed. If you play with the throttle it eventually goes fully into gear after a few seconds with a faint clunk and you get full drive being transmitted.
There is oil in the gearbox, I have measured the recommended travel and it's OK, have even tried adjusting the cable travel each way but with no success. It seems like the gaerbox is sticking internally as it usually goes in after a few seconds. Not sure of the internal arrangement as I only have the handbook which of course tells you nothing about the internals etc. are there dog-clutches or friction plates internally?
Any idea what the problem is?

dickh
I'd rather be sailing...

 

[miket]

Why not call Hurth/ ZF and ask in their technical department.
I found them extremely helpful.

 

[airbubble]

sorry to say that if indeed the cable-lever adjustment is correct, (best tried with the cable unclipped, move the lever by hand) its the clutch mechanism (plates) that have worn out.
Take it out and ZF will have to renew the plates.

 

[Guest]

My memory suggests that the sintered bronze thrust washer may have worn out. Long time since I have worked on Hurth boxes because to be brutally honest they are best avoided. Repairs may be expensive and it is often the case that, if the box is well worn anyway, a new box may be the most sensible option. Talk to Bill Carver in Manchester (0161 480 0320).

 

[dickh]

Thanks for all the info, I have spoken to the agents in Norwich who basically say that by the time the gearbox is repaired, with the cost of spares and labour it is cheaper to fit a new box.
Apparently Hurth only sell individual parts whereas ASAP Supplies do a Clutch Plate Kit and Thrust Washer for about £100, which sounds a realistic cost for me to rebuild it, but I don't have a Workshop Manual.

It was interesting that he said the boxes only last about 1000 hrs on Broads boats(mine has done 600hrs)and that Perkins always fitted undersized gearboxes!!

Does anyone have a Workshop Manual for the HBW 50 Gearbox that I could borrow and photocopy? or buy if you no longer have a need for it.

dickh
I'd rather be sailing...

 

[billywilliams]

I have recently suffered the same problem with a Hurth Velvet Drive box mated to a Perkins Prima 50 engine with less than 500 hours from new! I also received and accepted the same advice (parts unobtainable/expensive - cheaper to replace) and renewed the box at a total cost of £900!!! Billy Williams

 

[dickh]

Thanks for the reply, as a new box is £550,(SHMBO spotted my spreadsheet which detailed what I had spent this year on the boat and was horrified! - glad she didn't see last years, that was almost double!!)
I will first strip the box and find out what has gone and repair it if I can - hence my request for a Workshop Manual... ASAP Supplies do a 'copy' clutch repair kit at a reasonable price and this is probably the route I will take.

dickh
I'd rather be sailing...

 

[Johnjo]

Dick
Had same problem, was brass spacer worn causing clutch plates
to slip, Easely reconisable problem, Could see where the heat
build up caused by the slipping clutch had blued the metal,
Bought all parts seperatly from local agent, they also supplied
a assembly sheet, straight foreward job.
Mike

 

[dickh]

Mike27, thanks for the reply, it sounds as though it won't be a horrendous job. Could you send me a copy of the assembly sheet if you still have it? I will PM you with my address and put a donation in the RNLI box.

dickh
I'd rather be sailing...

 

[dickh]

Mike, can't seem to send you a PM - says you are not accepting PM's - can you PM me with your phone no and we will talk.

dickh
I'd rather be sailing...