Hydraulic Gearboxes - how to lock when sailing?

[Tim Good]

Ok this is a 2nd post on the subject but I'll try and be more concise.

On a boat with a hydraulic gearbox, Hurth HBW 250 in this case, when sailing how can it be locked? Can I just turn the engine off whilst in gear?

If i let the prop spin while off will that cause issues on a hydraulic box?

 

[sailorman]

fit a folding/feathering prop
i have a PRM 150 box

 

[Strathglass]

On my PRM hydraulic gearbox it is possible to lock it in gear and bypass all the hydraulics if it looses drive. Involves taking the top off it.
I don't know if the same with your box.

 

[Tim Good]

fit a folding/feathering prop
i have a PRM 150 box

Yeah I have one actually but boat had a shaft brake and basically I'm trying to figure out if I can get shot of it without any danger of damaging the gearbox if it doesn't fully feather / causes the shaft to turn.

 

[sailorman]

Yeah I have one actually but boat had a shaft brake and basically I'm trying to figure out if I can get shot of it without any danger of damaging the gearbox if it doesn't fully feather / causes the shaft to turn.

the box need lubing if freewheeling.
full PRM details online, even full drgs

mine drives a MaxProp

 

[RobbieW]

I think I'd keep the shaft brake. I have a Technodrive TM345 with a Brunton autoprop attached, if thats left to its own devices the prop freewheels and spins the shaft - heating the gearbox oil and making a row. In gear or out of gear makes no difference because theres no oil pressure to engage the box drive, I guess the pressure derives from the engine side of the box.

My solution is quite low tech - theres a piece of string that loops onto one of the coupling bolts to stop it turning and let the blades align. The string threads through one of the timbers surrounding the drive coupling. The prop freewheels in reverse so if you forget to remove the string before engaging drive it 'SHOULD' just drop off the bolt.

 

[Tim Good]

I think I'd keep the shaft brake. I have a Technodrive TM345 with a Brunton autoprop attached, if thats left to its own devices the prop freewheels and spins the shaft - heating the gearbox oil and making a row. In gear or out of gear makes no difference because theres no oil pressure to engage the box drive, I guess the pressure derives from the engine side of the box.

My solution is quite low tech - theres a piece of string that loops onto one of the coupling bolts to stop it turning and let the blades align. The string threads through one of the timbers surrounding the drive coupling. The prop freewheels in reverse so if you forget to remove the string before engaging drive it 'SHOULD' just drop off the bolt.

Not totally following but I think I know what you're saying.

 

[SAMYL]

Bear in mind that 'hydraulic' boxes are not really hydraulic in that the drive is normal mechanical and the hydraulic part only operates the clutches for the gear change.

PRMs can be locked as described above as a 'get you home' measure, but it does require removal of the top cover which is not ideal.

I don't think letting the prop spin will cause any damage, normal lubrication will still continue within the box with the shaft turning. Maybe someone will be along who thinks otherwise.

 

[Tranona]

You need to find out whether the shaft actually turns when the engine is off. Different props behave in different ways. My folder stays folded, but some feathering props may still turn slowly. Maybe the owner fitted the shaft brake because the shaft spun - you won't know until you try the boat.

 

[Barnacle Bill]

I had this problem for ages, with a hydraulic box and a Maxprop. The Maxprop just wouldn't fold because the shaft needed to be stopped and the box wouldn't do that.

Having tried all sorts of solutions - shaft brake etc -the answer is to switch the engine off while it is driving in forward gear. This will briefly stop the shaft and cause the Maxprop to feather.

 

[Tim Good]

I had this problem for ages, with a hydraulic box and a Maxprop. The Maxprop just wouldn't fold because the shaft needed to be stopped and the box wouldn't do that.

Having tried all sorts of solutions - shaft brake etc -the answer is to switch the engine off while it is driving in forward gear. This will briefly stop the shaft and cause the Maxprop to feather.

Thanks for this. Ok so bottom line is that I can disengage the shaft lock without risking too much damage to gearbox if it does end up turning the prop which will get the boat from purchase place back to mooring (200nm). Then I can try Barnacle Bills method. If that fails then I need to look at a new shaftlock.

That'll do as a solution.