Saildrive prop lost - but how?

[Thresher]

My prop fell off last summer when I went to reverse out of my berth, I retrieved it from the mud but the centre bolt and cone were long gone. There had been a knocking from the prop previously that I had been meaning to look into.
I have since bought replacements but how do I know it will not happen again?
I accept that I may not have tightened the whole assembly up enough before the boat went in to the water but as there is no split pin I sort of assumed that the action of the prop somehow stiffened the whole thing up. Assumed wrongly I think! Does anyone know how tight you should get it, has anyone had this happen to them?

 

[davierobb]

Same thing happened to me on a Jan 43. Drill hole and use split pin, the folded locking washer is not 100% guaranteed. Also I watched the marine engineer do this and he tightened the cone at least 1/2 to 1 full turn more than I would have. I would say he knows best. You can drill the cone and shaft using a cordless drill, just use new drill bit and a lubricant on the bit every few seconds, wd40 or similar works ok.

The prop has not fallen of despite the boat being used 10 months of the year for training and having covered tens of thousands of miles since.

 

[gianenrico]

IMHO there MUST be a locking pin through the central nut and slotted bolt: sorry folks, I annually greased my SD for 16 years during overhaul, and allways extracted and replaced the SS pin (streigthening and then bending its tips), /forums/images/graemlins/blush.gif

 

[Malcb]

We lost two props off a Sailing Association Warrior 40 with Volvo Sail Drive. Didn't like the way that the prop was, presumable, locked on. We would have preferred a hole drilled at right angles to the shaft and a split pin to lock the cone on.

Eventually, after a refit we changed to a feathering prop. This is fitted differently, I can't remember how as I didn't see the boat before it went back in the water, but I will tomorrow, as it is being lifted.

I suspect that what was happening was in how the prop reacted to the shaft when reverse was selected. We suspected that, as it is a boat which is 'chartered' out to members of the association, that they were none too carefull when selecting reverse. With the result that the prop 'slammed' backwards against the cone, and eventually loosened it to such a degree that the cone and prop eventually flew backwards when reverse was selected.

Of course, Volvo completely denied thatvthat was happening, however as the boat belongs to a saoling association it is out on the water more than it is moored alongside. So the engine got/gets a lot of use.

 

[Ross1]

It is not uncommon for props to fall of unexpectedly! If you read the small print on invoices etc from marine engineers most have a disclaimer against props falling off if they have fitted them. Otherwise it would cost them a fortune!

As mentioned above it is not helped with the 'slamming' of the prop back and forth through the gears, also snagging rope etc... can cause it to put strain on the nut and break the lock!

Not all props have the option of fitting a retaining split pin, you must make sure that thread lock is used. The thread lock must be used correctly and the nut tight! the thread lock then needs to be allowed to dry before the boat is put back in the water. Only takes a short while but I have seen it left until the last minute to change an anode or such and then pop the prop back on! This being said your prop should be fine as many hundred other yachts and their props.

 

[tom52]

It sound as though you are describing the standard Volvo SD fixed prop.
My understanding is that having hand threaded the cone on and tightenen up using a tommy bar, the central bolt is then inserted and tightened which means the bolt should act like a locking nut. Thats why there is no split pin arrangement.
Although whenever I replace my prop at the begining of the season I often think how re assuring it would be to have a split pin type arrangement.
Your story has now confirmed my worst fears and given me something else to worry about out of sight below the waterline !

 

[Thresher]

Yes it is exactly as you describe. I don't slam my boat into reverse and I haven't snagged any ropes this year but it occurs to me that when sailing, the constant flow over water over the prop locked in neutral must work against the cone and locking nut.
I don't know! I guess I'll just tighten the thing to buggery, I can't see loctite doing much with all that grease around.
Good thing I didn't lose the prop as well, the cone kit cost nearly £80 and I still have to buy the SS line cutting dish, that'll cost about £70 I think, god knows what a prop costs.

Thanks all.