Propeller locking or not?

[dkd 3]

Been watching this conversation with interest.

 

As a Marine Engineer it has to do with design of the clutch arrangements and lubrication, but more with the lub of the thrust faces of the box more than anything else.

 

But design design and design are the controlling factors, ..... clutches, thrust "block" and lubrication arrangements. It does not matter whether it is recreational or commercial the requirements are the same

[alibaba 79]

ah-damn! I'm now feeling thick! The problem wasn't in the gearbox at all. I got into the water and found that the prop could be turned on the shaft. The shaft keyway had broken. I did consider that but couldn't see how the prop could turn one way and not the other.

I've finally got my head around it. When in reverse the prop was pushed off the taper and was free to spin. When in forward, there was enough friction to turn the prop slightly and that meant that it was pushed forward onto the taper, and the more power applied the more it tightened up!

that explains how I could have drive one way and not the other.

solution is to remove prop and replace the keyway. b......r!

[wheels 543]

Congrats on finding the problem

[alibaba 79]

The horse's mouth, aka the engineer at the Yanmar dealer, says that no gearbox should be locked while sailing, but that the shaft should be locked with a shaft brake.

I guess that's definitive then.

[Chewing Gum 17]

Not sure why that would be - did he give a reason?

Anyway if you have a feathering or folding prop putting it into gear momentarily will align the blades with the water flow and stop the shaft spinning and then you can return it to neutral and the shaft will not spin while sailing.

We have done this for years with a Yanmar 4JH2TE 60hp with no problems.

Of course this will only work with a mechanical box (not hydraulic).

[alibaba 79]

quite right, but I have a fixed three blade prop. Guess I had better save my pennies for a folder, but they aren't the greatest in reverse.

[Chewing Gum 17]

If you get a 3 blade feathering or similar eg autostream or kiwiprop they work well in reverse