prop lock

[kunyang]

I am looking at a new (to me) moddy 42. It has a Perkins engine, and a prop lock. There looks to be a problem with the prop lock. It basically looks like a car disk brake, but the hydraulic pipe has become disconnected. Is this system ok, what else could i use. I understand that you do need this for a hydraulic gear box?

Any advise is apprciated.

Dave

 

[RobbieW]

I'd agree that its necessary having a hydraulic gearbox too, combined with an Autoprop which freewheels over about 5 knots. My lock is simply a bit of line from a floor member above the drive coupling that loops over a coupling bolt, it can be a bugger to remove at speed but fortunately the prop freewheels backwards so if I cant shift it no damage is done by motoring forwards. Most of these devices that I've read about suggest that the boat needs to be going slow to engage, which fits with my experience - perhaps the previous owner doesnt understand the constraints of the installed system?

I think I'd ask how long its been disconnected and how many hours run without it. If left to run free, my gearbox gets hot as the oil cooler is inoperative without the engine running; it also puts more hours on the prop bearings than would otherwise be the case, that can be a factor if you spend a lot of time on the boat.

 

[pcatterall]

I plan to fit a lock to my perkins 4108 ( which has a Thames marine hydro box) I hope to just use an adapted Cycle brake as I can stop the prop with my hand on the shaft.
however if yu have the disc allready on the shaft then it would seem logical to just get it working properly as I also understand that you should stop this gearbox.
You may worry about forgetting to unlock the brake before engaging gear or there may be some clever over ride on your system to prevent this. In my set up I think I would just have burning brake blocks!!
It only above 4knots that my prop starts to spin but the noise is distracting if nothing else

 

[kunyang]

if I replace the prop with a feathering type, would that suffice?

 

[Tranona]

if I replace the prop with a feathering type, would that suffice?

You may not get it to feather if you cannot lock the prop. It is often necessary to select reverse to stop the shaft turning, prop feathers and then back into neutral.

 

[ghostlymoron]

'It only above 4knots that my prop starts to spin but the noise is distracting if nothing else'
The noise is very annoying in your aft cabin!

 

[Tim Good]

I have a Perkins M90 witha Velvet Drive and yes the old prop would spin because of the hydraulic box unless the Shaft Lock was engaged. Pain in the arse so we now have a Variprop which feathers. I recommend you go down that route.

If you turn the engine off which in gear then there is enough hydraulic pressure left to feather the prop before it tries to free wheel.