Make sure your nuts are done up very tight - Salutory note with a dash of puckering on the side

[Lightwave395]

I fitted a PSS shaft seal over the winter with the boat in Cowes, excellent piece of kit, we were launched and then subsequently went to Roscoff last weekend where the boat is berthed.
Of the 26 hour voyage, around 8 or so were motor sailing, mostly during the night and being a bit paranoid I checked the seal several times during the trip – absolutely dry and working perfectly.
When we arrived, we re-fuelled and were gently motoring downtide into the marina looking for our berth when two little Merry Fishers came hurling out in front of us causing a serious emergency stop with full throttle in reverse.
Having exchanged pleasantries with them we nudged into our berth, secured the boat and my crew went down to put the kettle on followed by a shriek and the news there were 3 or 4 litres of water on the floor in the aft cabin. I went down below, lifted the floor panel and found that the shaft had moved backwards and had about 15mm left in the flange, presumedly due to the full throttle reverse manoeuvre and it must have been the anode preventing it from dropping out altogether. The rubber bellows is damaged being squashed hard between the rotor and the stern tube but thankfully the water appears to have come in during the incident and none subsequently appeared – the boat is out of the water now and I’ll be returning this week with the parts to repair

The propshaft flange is standard 3YM30 I believe, 4 bolts onto the gearbox flange, and the shaft fits in a clam like clamp with itself 4 Cap head bolts and 2 grub screws, one each side. The bolts were done up really tight ( I thought ) , the grub screws were too and threadlocked

The conclusion is they clearly weren’t done up tight enough – when I dismantled the clamp to fit the new shaft seal last November the Cap head of one bolt sheared as it was so tight. They’re all going to be bloody tight when I put it back together, I thought I’d maybe drill an indent where the grubscrews go too
Yes I know it was my own fault but any other hints / constructive comments welcomed

 

[andsarkit]

I had a similar incident with my 1GM. When I installed it a 'marine engineer' assured me that the standard 20mm coupling would be fine on a 3/4" shaft if I did it up tight. I wasn't sure and added a couple of grub screws.
About 20 years later when I reversed hard to dig in the anchor, the shaft moved back and the propellor bent as it took a chunk out of the rudder. That was a rather expensive lesson and I now have a proper 3/4" coupling from R&D marine.
I think a big indent for a grub screw would be a good solution.
The standard Yanmar coupling uses cap head bolts and you can't get much torque on them with a normal length hex key. The R&D one uses high tensile bolts that you can tighten with a long ratchet socket. R&D recommended torque is 54Nm (40 lbsft) which you would not achieve with a hex key in a Yanmar cap head bolt.

 

[[70521]]

I had a similar incident with my 1GM. When I installed it a 'marine engineer' assured me that the standard 20mm coupling would be fine on a 3/4" shaft if I did it up tight. I wasn't sure and added a couple of grub screws.

Rant

A fitter or a mechanic not an engineer I suspect. A professional engineer would have specified the correct size coupling.

Gosh is there still imperial kit about? I was 60 in March and was educated and worked wholly in metric. My late father a time served Clydeside apprentice then a merchant navy engineering officer welcomed the move to metric; although worked in both.

Rant over.

 

[Tranona]

Gosh is there still imperial kit about? I was 60 in March and was educated and worked wholly in metric. My late father a time served Clydeside apprentice then a merchant navy engineering officer welcomed the move to metric; although worked in both.

Rant over.

Yes. No reason why not, particularly for stern gear as nothing is interchangeable. That is if you have a 3/4" or a 1" shaft as most small older boats do nothing metric will fit. to change you have to change coupling, inboard bearing shaft seal and outboard bearing. I am fitting new stern gear to my GH and was originally going to fit an imperial shaft, but the coupling has a long delivery time in imperial whereas the metric is ex stock (and more expensive!). No functional difference, just convenience.

 

[Bilgediver]

Rant

A fitter or a mechanic not an engineer I suspect. A professional engineer would have specified the correct size coupling.

Gosh is there still imperial kit about? I was 60 in March and was educated and worked wholly in metric. My late father a time served Clydeside apprentice then a merchant navy engineering officer welcomed the move to metric; although worked in both.

Rant over.

Many boats still have imperial size drive items. Just have to identify which you have . Is it 25mm or 25.4 mm ? The latter is 1" so buy seals, couplings and bearings to suite. They are available

 

[Daydream believer]

Of the 26 hour voyage, around 8 or so were motor sailing, comments welcomed

Wondered how you averaged 6.45Kts. You never told us that bit. That was cheating
Glad you managed to save the day though. Not what you want. At least Roscoff has the facilities & ferries home etc. So not all lost.
Have to be aware of hidden costs. A friend of mine was hauled dead cheap in Le Treport & told that he could stay for a very cheap rate. However, when it came to paying the bill they charged a fortune for the hire of the cradle & the crane lift Back into the water

 

[Lightwave395]

Wondered how you averaged 6.45Kts. You never told us that bit. That was cheating
Glad you managed to save the day though. Not what you want. At least Roscoff has the facilities & ferries home etc. So not all lost.
Have to be aware of hidden costs. A friend of mine was hauled dead cheap in Le Treport & told that he could stay for a very cheap rate. However, when it came to paying the bill they charged a fortune for the hire of the cradle & the crane lift Back into the water

Yes, I get one free lift with my berthing contract but I hadn't planned to use it so quickly...
I think the bit that helped most was an ebb spring tide, we were sailing at 8 knots, occassionally 10, until past Portland when the tide changed which then pushed us down more towards Roscoff, we also got across the shipping lanes without hindrance, which hasn't happened the last couple of times I've crossed the channel.
I should add it still is a quick boat, even laden down in cruising mode and is certainly in it's element when cracked off a bit, the forecast Easterly never materialised, at least not in our bit of the channel, but the South Easterly we had was fine and the last few hours were more SSE

 

[[2574]]

I fitted a PSS shaft seal over the winter with the boat in Cowes, excellent piece of kit, we were launched and then subsequently went to Roscoff last weekend where the boat is berthed.
Of the 26 hour voyage, around 8 or so were motor sailing, mostly during the night and being a bit paranoid I checked the seal several times during the trip – absolutely dry and working perfectly.
When we arrived, we re-fuelled and were gently motoring downtide into the marina looking for our berth when two little Merry Fishers came hurling out in front of us causing a serious emergency stop with full throttle in reverse.
Having exchanged pleasantries with them we nudged into our berth, secured the boat and my crew went down to put the kettle on followed by a shriek and the news there were 3 or 4 litres of water on the floor in the aft cabin. I went down below, lifted the floor panel and found that the shaft had moved backwards and had about 15mm left in the flange, presumedly due to the full throttle reverse manoeuvre and it must have been the anode preventing it from dropping out altogether. The rubber bellows is damaged being squashed hard between the rotor and the stern tube but thankfully the water appears to have come in during the incident and none subsequently appeared – the boat is out of the water now and I’ll be returning this week with the parts to repair

The propshaft flange is standard 3YM30 I believe, 4 bolts onto the gearbox flange, and the shaft fits in a clam like clamp with itself 4 Cap head bolts and 2 grub screws, one each side. The bolts were done up really tight ( I thought ) , the grub screws were too and threadlocked

The conclusion is they clearly weren’t done up tight enough – when I dismantled the clamp to fit the new shaft seal last November the Cap head of one bolt sheared as it was so tight. They’re all going to be bloody tight when I put it back together, I thought I’d maybe drill an indent where the grubscrews go too
Yes I know it was my own fault but any other hints / constructive comments welcomed

Interesting. We have an Aquadrive unit on our new to us boat. Our very first pre-departure checks (heading around Mull of Kintyre in November) identified two of six bolts to be nearly falling out. Tightened up as best I could with an Allen key. Fast forward 18 months - we’ve now discovered that the loose bolts have done damage and we’re having to replace the Aquadrive unit, the propshaft, thrust bearing, shaft seal and cutless bearing. It’s a nightmare, keep those bolts tight! The Aquadrive bolts should be torqued to 50ft lbs, impossible with an Allen key. They should also have Loctite applied. There’s a full report on the Malo owners group if anyone is interested.

 

[Lightwave395]

Interesting. We have an Aquadrive unit on our new to us boat. Our very first pre-departure checks (heading around Mull of Kintyre in November) identified two of six bolts to be nearly falling out. Tightened up as best I could with an Allen key. Fast forward 18 months - we’ve now discovered that the loose bolts have done damage and we’re having to replace the Aquadrive unit, the propshaft, thrust bearing, shaft seal and cutless bearing. It’s a nightmare, keep those bolts tight! The Aquadrive bolts should be torqued to 50ft lbs, impossible with an Allen key. They should also have Loctite applied. There’s a full report on the Malo owners group if anyone is interested.

Indeed, I have bought an allen key socket so should be able to get it tighter but I'll be reversing gently for a while I think !

 

[oldmanofthehills]

I had similar incident after undo then redoing a prop shaft on a yanmar 10hp in order to get at cutlass bearing fitting.

Went astern right outside the entrance to Cardiff Barrage and it slipped uncontrollably having shifted. Barrage wanted us to call the life boat or some nonsense, but we were really not in anyones way so I ferreted around for an allen key and pushed it back together and carefully tightened things using extension tube on the key. When back in home port bought a socket set 7mm allen key and did the proper job.

 

[jwfrary]

Such a common thing I have seen it quite a lot, a friends a boat nearly sank on its mooring the water was up to the top of the berths after the shaft slid out, was just resting on the rudder requiring a chilly February dip in the marina in the middle of the night to remedy!

It is a bit of a design flaw with the yanmar coupling.

I prefer the centa type AM couplings which fit with a taper lock, though they do suffer from being over tightened!

The R&D split coupling are good value for money though big torque wrench required!

 

[LadyInBed]

A pipe clamp (or two) on the shaft close to the stern gland is a good idea.

 

[Robin]

A pipe clamp (or two) on the shaft close to the stern gland is a good idea.

We have had 2 such seals on separate boats in both cases jubilee clips were added as extra security. However on the second boat the coupling was also drilled and through bolted but it was a 4JHE Yanmar with somewhat more grunt and with a bigger diameter shaft. Actually thinking about it now I remember it was fitted by the marine engineer at our then YC in Poole when the PSS one was fitted as a replacement for a failed DSS one which had leaked under load on the original delivery trip .

 

[Boater Sam]

The grub screws will do nothing unless you drill indents for them in the shaft. They will not self indent into steel, especially stainless steel.

A little engineering knowledge can be a dangerous thing.

 

[Concerto]

Yes, I get one free lift with my berthing contract but I hadn't planned to use it so quickly...
I think the bit that helped most was an ebb spring tide, we were sailing at 8 knots, occassionally 10, until past Portland when the tide changed which then pushed us down more towards Roscoff, we also got across the shipping lanes without hindrance, which hasn't happened the last couple of times I've crossed the channel.
I should add it still is a quick boat, even laden down in cruising mode and is certainly in it's element when cracked off a bit, the forecast Easterly never materialised, at least not in our bit of the channel, but the South Easterly we had was fine and the last few hours were more SSE

View attachment 133952

Reading you Marine Traffic Report, I was surprised your beam is only 3 metres. My Fulmar is 3.33m.

What happened to you is not uncommon. I remember talking to someone who has a similar experience, but he was off the coast of Brazil in rough weather. The coupling bolts holding the shaft had come loose. The shaft dropped aft and jammed the rudder on full lock. There was nothing he could do and eventually he started taking on lots of water and had to abandon to his liferaft. His yacht sunk and luckily he was rescued having lost virtually everything.

 

[Lightwave395]

Reading you Marine Traffic Report, I was surprised your beam is only 3 metres. My Fulmar is 3.33m.

What happened to you is not uncommon. I remember talking to someone who has a similar experience, but he was off the coast of Brazil in rough weather. The coupling bolts holding the shaft had come loose. The shaft dropped aft and jammed the rudder on full lock. There was nothing he could do and eventually he started taking on lots of water and had to abandon to his liferaft. His yacht sunk and luckily he was rescued having lost virtually everything.

I think I made a typo, the beam is 3.65M ! I think that must be mis-typed in the AIS config as there deson't seem to be anywhere I can change it on the website...

 

[roaringgirl]

The idiot who fitted our PSS didn't do the propshaft/transmission clamp up tight enough, with similar results. After emergency haulout, he swore blind it wasn't him who'd done it, until I produced the receipt for his work, at which point he told me I must have wrapped a rope around the prop to make it fail (I hadn't). I'd just finished a 1000 mile trip Edinburgh to Gothenburg and back with the family and told him it was lucky it had only failed in the final few miles. Then he got the hump and refused to put it right until I apologised!

 

[colind3782]

Reading this thread and after forty years of spannering light aircraft, I wondered "why are critical fastenings on boats not wire-locked?" I supose Nyloc nuts would help as long as the nuts are torqued correctly in the first place.

 

[[2574]]

Reading this thread and after forty years of spannering light aircraft, I wondered "why are critical fastenings on boats not wire-locked?" I supose Nyloc nuts would help as long as the nuts are torqued correctly in the first place.

The manufacturer of Aquadrive instructs that Loctite be used. Is that as reliable as wire locking?

 

[Lightwave395]

I locktited mine, unfortunately they just weren't tight enough in the first place...!

In a somewhat weak defence when I removed the old Orbitrade rubber seal ( fitted 4 years ago by a 'marine engineer' ) to fit the PSS replacement there were no indents for the grub screws so I carried on regardless. However, as mentioned above, the shaft clamp bolts were done up so tight one sheared when I tried to undo it