Can a hydraulic gearbox have a fixed prop?

[david36]

I am thinking of replacing my rubbish mecanical gearbox (MS25A, failing for the second time after 1200 hours) with a hydraulic one (HS25A) on my Volvo D2-55 engine. I keep getting conflicting advice as to whether or not I need to also change my existing fixed 3 blade prop for a folding/feathering type. Aside from the matter of the vast cost of a new prop and its subsequent maintenance, I would prefer to keep the fixed one as I find the instant, strong pro- walk in reverse quite useful now that I have sort of got the hang of it. Do I need a new prop to go with the new gearbox?

 

[Deleted member 36384]

No you dont need to change the prop. However, the prop can not be locked by placing the gear lever in reverse. The spinning prop has the potential to wear out the gear box because the lubricating oil is distributed when the engine is on and causes the gearbox to pump oil.

It is likely though that the gearbox instructions will say that you need to run the engine every so often to redistribute the oil around the gear box. Alternatively you can instal a shaft break. There are plenty of home made jobs from simple mole grips on the shaft to disk brake devices that can be purchased off the shelf, to adapted motorcycle disc brakes.

The above is a general comment on Hydraulic Gearboxes and is my experience from my own Borg Velvet Drive hydraulic gearbox. I have a large 3 bladed prop which spins the gearbox when the engine is off if the boat speed is above 3 kts.

Your particular gearbox may be different so best to ask the manufacturer. Hope this helps.

 

[michael_w]

Depends if the characteristics of the new gearbox suit...It's no good having a RH prop if the gearbox needs a LH one!

When I repowered I used a PRM 150 gearbox because it was rated to work in either direction. Owing to an offset P bracket and other stern gear it was essential that I used a LH prop. All modern mechanical gearboxes are RH!

Within reason, any gearbox will fit any engine. The mounting holes are to an SAE standard.

 

[david36]

Thank you for the helpful comments. I think that I will try keeping my existing prop and see how we progress.
Fair winds.

 

[JoSaDro]

Within reason, any gearbox will fit any engine. The mounting holes are to an SAE standard.

Does this mean I can use(almost) any gearbox for my D2-75?
I have trouble finding a reasonable priced gearbox (HS25A). There are a lot of other gearboxes for sale secondhand.

Hope you can help me with this.

Thanks