Possible Hurth 50 gearbox problem

[atrman]

Helo,

I am new to sail boat engines and have what seems to be a problem with the gearbox, whilst the engine is off and the gearbox in neutral, the engine moves on its mount, it is as if the propeller is still engaged and turning over the engine. Can this be so?

The engine is a Kubota Z 600 B and the gearbox is a Hurth 50.

Any advice would be most welcome.

Steve

 

[rob2]

The reversal of the mechanicl advantage of your gearing means that a freewheeling prop will not turn over the engine. As you are in neutral, the prop will be turning, driven by the waterflow, and any movement in the shaft will be seen as movement at the engine mounts.

Consider how the shaft is supported. Many installation have a cutless bearing close to the prop, a flexible hose with sealing gland inboard and an engine bolted to the end on flexible mounts. So the two fixed points are the cutless bearing and the engine, you'd expect the engine to damp a lot of the movement, but it will move. If it proves to be excessive, i.e. the cutless wears too fast or shaft vibrations cannot be eliminated, then the two items which could be replaced are the cutless and the engine mounts. When out of the water check for side play in the bearing. Difficult to give any judgement on engine mounts but they do soften with age and may delaminate.

Rob.

 

[PlankWalker]

Its normal for the propeller to rotate if left in neutral while sailing,

Most people leave it in reverse gear to stop wear on the shaft and gearbox.

No way should your engine move though, I would check your engine mounts if this continues.

Plank

 

[atrman]

Thank you for the fast reply Rob, that has put my mind at rest and will look at the prop when out of the water soon.

Steve

 

[atrman]

Thanks for the reply Plank, I will try leaving the prop in reverse and see what happens.

Steve

 

[nedmin]

Sounds as if your engines out of line with the prop shaft,could be as mentioned ,mounts, or if not wants lining up.If its moving the engine your props not turning as easy as it should so you will be losing speed.Assuming your sailing.

 

[atrman]

Thanks for the info nedmin, I will have to ge that looked at when its out of water next.