Rattly Technidrive gearbox, removal with boat in water...is it possible?

[Iain C]

I've got a noise coming from my gearbox (technodrive) which sounds like a bit like an inconsistent rattle...a nut in an empty bean can that gets louder with increased revs (but disappears in neutral regardless of revs so it's definitely the box). Golden Arrow marine say it's most likely to be the drive plate with some broken springs (sounds plausible) and they will need the old one before they can advise on a replacement cost.

Boat is a fin keel Sabre 27. Access to the gearbox is excellent, through a 500x500 Lewmar hatch in the cockpit floor. They advise that to remove the box, I will need to get the boat ashore, however that is a right PITA and also very expensive, especially if it turns out it's not the drive plate.

But thinking about this, surely if I dry the boat out on my club's scrubbing piles, move the shaft back a bit by undoing the drive coupling, get the box out, and then devise a method to hold the shaft in roughly the right place fore and aft, that should be OK when the tide comes back in?

Am I right in saying the shaft is uniform the whole way along, so provided it can't fall out (impossible due to prop and skeg) the boat isn't going going to sink?

I've never done this before so I just want to be aware of any potential pitfalls. Also, if anyone has any ideas on the rattle, please shout!

Thanks in advance.

 

[Steve_N]

I've removed a gearbox while afloat before - and left the boat afloat without gearbox for a month or so while the box was overhauled.
I just made up a wooden support to bolt onto the shaft's drive flange to hold it firmly in the correct position while the box was missing.
No problem in pushing the shaft back to get some clearance.

 

[Hadenough]

I've just taken mine out on in the water, on a pontoon I might add. I had to move the shaft back 100mm and keep it in the same position because of an ambasador rope stripper that needs to realign properly. Even that will be touch and go with a day of clear water and an underwater camera. But if you don't have that problem, other than making sure the shaft can't slide out (jubilee clip) I don't see a problem.

 

[prv]

I can't see why you'd need to even dry out on the piles. The only reason might have been the need to move the shaft a fair way aft to get the gearbox off, which on some boats wouldn't be possible due to the prop hitting the skeg or rudder. But a quick google suggests a Sabre 27 should have plenty of space to slide the shaft back.

We had this happen involuntarily on Kindred Spirit (gearbox output flange parted company with the rest of the box) and the shaft slid back until the prop was resting on the rudder. We spent most of the next day hanging through the hatch messing about with gearbox and shaft, and never a hint of a leak through the stern gland.

I guess if your stern gland is something fancy with face seals, you'll need to slide it along somehow and that might leak a bit while you're doing it. But a stuffing box or lip seals ought to be fine.

Pete

 

[vyv_cox]

I have disconnected my prop shaft and pushed it back several time when I had a packed gland. I have also repacked the gland when afloat and removed engine and gearbox. Even with a PSS it would not be too much of a problem. It is surprising how little water comes through the gaps, which a rag wrapped around the gland will usually arrest.

 

[Iain C]

Brilliant, thanks for the replies all.

 

[PuffTheMagicDragon]

(1) Removal of the box while afloat should not be a problem if there is enough clear space for the prop.
(2) You mention that "it's most likely to be the drive plate with some broken springs". As far as I know, Technodrive boxes use a double cone clutch. The only spring that I recall is the one that holds the selector fork in a groove between the two cones. Of course, I am not familiar with all the models so yours might well be different. See if you can find a diagram on the internet so that you will know what to expect.