Hurth Gear box noisy when changing gear

[Horace42]

My Hurth gearbox engages gear, forward or reverse, with a loud clunk. .

In fact it sounds as though it 'slams' into gear no matter how gentle the gear lever is moved. Once in gear it runs quietly.

I appreciate the gearbox has an internal thrust plate assisted by oil pressure that helps push the gearwheels fully home, but there is no adjustment as such.

It is partly to do with engine speed, that in neutral is set at a minimum for smooth running - about 600 rpm - I can't run any slower because the engine leaps about on the rubber mounts.

I just wonder if other boaters have this problem ? - and maybe a cure please?

[Tony Brooks]

Buy a hydraulic PRM

 

Seriously my Spanish built ZF box cluncks into gear and it has done for years with no apparent ill effects. I think it tends to be a feature of mechanical gearboxes, especially ones that use a cone clutch because cone clutches are notorious for either being disengaged or engaged with little in between.

 

Hopefully Richard will be along with better advice.

[Tiggs]

Our Hurth box made no more noise than any other. Are you sure its the gearbox and not a loose prop shaft coupling?

[Tony Dunkley]

My Hurth gearbox engages gear, forward or reverse, with a loud clunk. .

In fact it sounds as though it 'slams' into gear no matter how gentle the gear lever is moved. Once in gear it runs quietly.

I appreciate the gearbox has an internal thrust plate assisted by oil pressure that helps push the gearwheels fully home, but there is no adjustment as such.

It is partly to do with engine speed, that in neutral is set at a minimum for smooth running - about 600 rpm - I can't run any slower because the engine leaps about on the rubber mounts.

I just wonder if other boaters have this problem ? - and maybe a cure please?

 

Be grateful that it does, . . . when Hurth boxes start engaging gears smoothly and quietly it either means they're about clapped out, and on the verge of failing to engage drive at all, or if you're lucky, just very long overdue for an oil change.

The harsh engagement is due to both clutches incorporating an identical mechanical self-servo feature which operates as the driven plates begin to engage with the drivers.

There is no pressurized oil operation or lubrication in Hurth mechanical boxes.

Edited August 12, 2016 by Tony Dunkley

[vicafloat]

I agree, my Hurth 150 allied to a Lister TS3 always clunks going into gear; and I have been advised by those

engineers who know that this is normal. Quiet operation is not!! My gearbox has had this characteristic clunk since we bought

our boat in 1999. Don't worry about it but do change the Auto transmission oil once every year.