Is My Gearbox On Its Way Out??

[makingplansfor]

I have a Hurth HBW 100 which I normally leave in neutral when sailing to allow the prop to spin. Whilst pottering in the engine bay while sailing I needed to lock the shaft so engaged the gearbox: when engaged forward, the shaft continued to spin but when engaged aft, it locked. This doesn't seem quite right to me as I would expect that when engaged the shaft should be locked irrespective of direction. There is no sign of clutch slippage when motoring so am I missing something or is the gearbox on its way out?

 

[30boat]

Mine , on a Beta 20 ,does that. And the previous Yanmar too. That's quite normal I'd think.

 

[Caer Urfa]

I have a Hurth HBW 100 which I normally leave in neutral when sailing to allow the prop to spin. Whilst pottering in the engine bay while sailing I needed to lock the shaft so engaged the gearbox: when engaged forward, the shaft continued to spin but when engaged aft, it locked. This doesn't seem quite right to me as I would expect that when engaged the shaft should be locked irrespective of direction. There is no sign of clutch slippage when motoring so am I missing something or is the gearbox on its way out?

I had the same gearbox a few years ago and had to change it for a ZF10M which is an exact replacement but with a very slight gear ration difference, however on both I also leave it in neutral when under sail and have not
had any problems, if it works ahead/astern ok when the engine is running be happy and leave it !

 

[Tranona]

Yes, quite normal. It is the prop turning the gear. If you want to stop it, put it in reverse.

 

[Salty John]

On a Hurth HBW box, when the engine is stopped and you are sailing, you should not put it in forward gear when going forward - use neutral or, to lock the prop, reverse. If you are sailing backwards you should put the box in forward gear or neutral

 

[Hydrozoan]

With a two blade folder (and a Hurth) on switching off I put it briefly into reverse to fold the prop. I'd expect forward to allow continued rotation and not force a fold.

 

[Salty John]

I'd expect forward to allow continued rotation and not force a fold.

And Hurth says this will damage the gearbox.

 

[Hydrozoan]

And Hurth says this will damage the gearbox.

Yes, I always leave it in neutral when sailing.

 

[makingplansfor]

Thanks for the responses, sounds like all is ok - I still don't get it though......

In gear surely means shaft attached to engine whether in reverse or forward - unless the clutch is direction sensitive and designed to slip in one direction?? Of course I could be overthinking it always a danger...... thinking!!

 

[ex-Gladys]

Try it when the boat is out, engage either gear and rotate the prop. Will go one way but not t'other...

 

[30boat]

There's a servo action in these conical clutches. That's probably what keeps the gearbox engaged in reverse when sailing and in forward or reverse when motoring.

 

[PabloPicasso]

There's a servo action in these conical clutches. That's probably what keeps the gearbox engaged in reverse when sailing and in forward or reverse when motoring.

That sounds plausible