Lost propeller from saildrive

[eddystone]

What would cause a saildrive to lose its propeller? It appeared to be properly secured when surveyed a few weeks ago. We had no previous experience of saildrives and sailed with engine in neutral. It came off when motor sailing then put into neutral to test speed under sail alone and then back into forward gear.
Confirmed there is no propeller with GoPro taped to boat hook.

 

[Daydream believer]

Has not been bolted on properly. Just because it LOOKS Ok does not mean that it is. Lots of vibration in a prop. Some props have a system of locking to prevent nuts releasing. some do not & need torquing up. In spite of that I once found the screws laying in the void between the thread end & the anode when the boat was laid up as they had started to vibrate loose. The prop would have fallen off in a few more hours of running.
Typically the previous owner may have had a folding prop & swopped it for an earlier fixed one for the sale & only loose fitted the replacement. Host of possibilities - But sod's law prevails

 

[Halo]

It will not have been mounted prop- perly

 

[colhel]

If you were motor sailing the prop could have been pushed further up the spline and thus taking pressure off the prop nut causing it to loosen. When I had a sail drive I had to make a spacer to go behind the prop or it would rub against the anode. Possibly worn spline or a mismatch spline

 

[Dunx]

I was a member of a club that lost two props from Hallberg34’s. The diagnosis was that the bolts were reused anfter maintenance and had stretched, causing them to loosen and fall out. Apparently the recommendation is a new bolt each time. I’m no expert but could it be the bolts are similar to stretch bolts used on car cylinder heads which are also single use?

 

[eddystone]

Thanks. The aluminium fixed bladed prop had lost most of its paint so not a great loss. Its replacement will be more valuable so like to keep it!

 

[Tranona]

Almost certainly the locking bolt was either not replaced with a new Volvo one or not installed with thread locker. The bolt then tends to unscrew allowing the cone to unscrew and the prop slides off the spline. A folder such as a Flexofold or featherer such as a Featherstream will have a much more positive locking system for the nut. The latter would be a good choice for your boat.

 

[wonkywinch]

Our Flexofold (on Yanmar SD25 sail drive) is an engineering marvel! Just got to remember to pop the boat into gear when sailing to assist folding and less drag.



The securing method is good also - https://25334245.fs1.hubspotusercontent-eu1.net/hubfs/25334245/3-blade US SD33_2024-1.pdf

 

[PabloPicasso]

I had a volvo folding prop on my last boat. It was locked on with a two tiered bolt and nut system and a tab washer which was not supposed to be reused.

 

[Daydream believer]

Our Flexofold (on Yanmar SD25 sail drive) is an engineering marvel! Just got to remember to pop the boat into gear when sailing to assist folding and less drag.

View attachment 194781

The securing method is good also - https://25334245.fs1.hubspotusercontent-eu1.net/hubfs/25334245/3-blade US SD33_2024-1.pdf

View attachment 194782

Item 9 in that diagram is a real pain. A friend of mine cannot get one out. The thing has a damaged hexagon so He has removed the saildrive complete & put another saildrive on with his old fix bladed prop untill we can work out how to get the screw out & remove the prop for service.
The allen key became slack so I warmed it with a blow lamp & belted it out of shape over an anvil. This made it tight in the screw but it sheared off in the head so we now have a stuck allen key in the screw that is corroded in the prop. It is a case of dissimilar metals. It would be advisable to loosen & remove from time to time to avoid my mates problem of corrosion. His was jammed up with barnacles which happened regularly- Poor design

 

[Daydream believer]

It will not have been mounted prop- perly

I reckon the OP has been shafted

 

[eddystone]

Almost certainly the locking bolt was either not replaced with a new Volvo one or not installed with thread locker. The bolt then tends to unscrew allowing the cone to unscrew and the prop slides off the spline. A folder such as a Flexofold or featherer such as a Featherstream will have a much more positive locking system for the nut. The latter would be a good choice for your boat.

I chose Featherstream last time I bought a prop only reservation is daughter will have this boat in the Caribbean and I’ll have make sure she checks the anode periodically and change it in the water if required; and a big box of spare bolts, grub screws and grease nipples as most of them will end up on the seabed.
Might look at Bruntons Autoprop if less maintenance

 

[Birdseye]

Item 9 in that diagram is a real pain. A friend of mine cannot get one out. The thing has a damaged hexagon so He has removed the saildrive complete & put another saildrive on with his old fix bladed prop untill we can work out how to get the screw out & remove the prop for service.
The allen key became slack so I warmed it with a blow lamp & belted it out of shape over an anvil. This made it tight in the screw but it sheared off in the head so we now have a stuck allen key in the screw that is corroded in the prop. It is a case of dissimilar metals. It would be advisable to loosen & remove from time to time to avoid my mates problem of corrosion. His was jammed up with barnacles which happened regularly- Poor design

Heat is your friend - or could be. With a different system but the same problem I had to resort to using a blowlamp to heat up the alloy. Because its thermal capacity was big, the blowlamp was left on a block of wood , heating away for 10 mins. Do it at your own risk but its the most likely way of seperating the two.