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Discussion Starter · #1 ·
You're probably all avid prop nut checkers, but if not, read on...

Went out for a trip on the bass from Herne Bay, today, and after a few drifts and a couple of fish we suddenly lost propulsion when Simon put the boat into reverse. My immediate fear was that the gearbox had failed, as we'd lost forward propulsion too. My jaw nearly hit the floor when I raised the engine to discover fresh air where the prop had been...

Lesson learned-even if you don't check the torque setting at least check the prop nut visually each trip. The engine had recently been serviced and it hadn't even occured to me that the prop-nut might work itself loose. The hub is a torque flow, and maybe these need more regular checking??

Anyway, the upshot of this is that, regrettably, for the first and hopefully only time, we had to call upon the services of the Whitstable Lifeboat. We maintain the boat fastidiously, so it hit me hard to have to waste these good folks time, but they could not have been friendlier and complimented us on the state of the boat and safety equipment. They were with us within the hour and towed us back to the Neptune Jetty. It's a very strange feeling being towed in your own boat, and not one I'd care to repeat...

I appreciate this was not a life threatening emergency, but in different circumstances it certainly could have been more serious. I was very glad of my new Icom VHF and it's only when you're in a bit of a fix that the real importance of these things hits home. Broadcast clarity makes a HUGE difference when you're really depending on it. In 7 years of boating it's the first time I've had to use the radio 'for real', and the benefits of doing the radio course are now very apparent. I did forget to press the button a couple of times though...:headhurt:

Anyway, a big thanks to Dave Parry and his crew for their help and professionalism.

One important check now added to my list...
 

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The prop nut should be held on by either a split pin, a tabbed washer or both. If the engine has recently been serviced is it possible that these were not put back ?
That would allow the prop to spin the nut off in reverse.

headlight
 

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There is no way your prop can come off if it is fitted correctly unless the shaft was to shear. Have a serious word with whoever serviced it for you last. It is secured to the shaft as stated by split pin and castellated nut or lock tabs. Get a new prop from your service engineer then find a new one to do future maintenance on the engine.
 

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It's a very strange feeling being towed in your own boat, and not one I'd care to repeat...


..
maybe time to acquire an auxiliary outboard,,,,,,,,,,,,,,
 

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The prop nut should be held on by either a split pin, a tabbed washer or both. If the engine has recently been serviced is it possible that these were not put back ?
That would allow the prop to spin the nut off in reverse.

headlight
The prop can't "Spin the nut off in reverse" it's on a spline. If the nut was there and no splitpin, it would take some time for the nut to work off.
If the prop came off as soon as reverse was selected, it sounds as though the nut wasn't put back on after the service.
 

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I'm pleased you got back safely Steve. From the comments it sounds like your service engineer let you down badly, check the manual to determine if it should have been a split pin or castlated nut before you have that conversation with him.
 

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At least you got in safely and i agree 100% its not a nice feeling getting towed in by the Lifeboat.

I had a pulley wheel sheer off last summer 20 mile out and lost all hydraulics and could not run the Engine either, funny enough that was just after a dealer "service". I reckon (but i could not proove it) that a ham fisted mechanic over-tightened the belts.

Whenever i have work done on my boat/engine i allways double check it myself these days. Rob
 

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Discussion Starter · #8 ·
The mechanic who's done all the work on the engine since I had the boat has always done an excellent job in the past and it's difficult to believe that he would have messed up on something like this, as I remember actually discussing with him the torque setting of 55 foot/pounds for the nut. He's always discussed the work on the engine in thorough detail and done a very thorough job. I'll probably have a straightforward chat with him and see if he can shed any light on it.

It's not a nice thought, but it is always possible that someone was trying to pinch the prop and got disturbed before they could finish the job, leaving it loose. The other possibility is that the tab washer was left out or even broke. I'm still baffled TBH as none of the scenarios really fully adds up...

It costs nothing to check it each time though, and from now on I'll treat it as another part of the pre-launch routine.

Like most small boat anglers I did give the option of an auxilliary some serious thought and discussed it with a good few boaters. The conclusion I came to was that a 4 or 5hp would be of little use when 20 plus miles from land. It would though give me a means of getting out of a shipping lane say, and for that reason alone, perhaps we'll have to reconsider it. The twin engine approach is probably beyond my pocket at the moment, but a pair of 50s might be the best solution of all. I'm sure it would be juicier though...
 

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The mechanic who's done all the work on the engine since I had the boat has always done an excellent job in the past and it's difficult to believe that he would have messed up on something like this, as I remember actually discussing with him the torque setting of 55 foot/pounds for the nut. He's always discussed the work on the engine in thorough detail and done a very thorough job. I'll probably have a straightforward chat with him and see if he can shed any light on it.

It's not a nice thought, but it is always possible that someone was trying to pinch the prop and got disturbed before they could finish the job, leaving it loose. The other possibility is that the tab washer was left out or even broke. I'm still baffled TBH as none of the scenarios really fully adds up...

It costs nothing to check it each time though, and from now on I'll treat it as another part of the pre-launch routine.

Like most small boat anglers I did give the option of an auxilliary some serious thought and discussed it with a good few boaters. The conclusion I came to was that a 4 or 5hp would be of little use when 20 plus miles from land. It would though give me a means of getting out of a shipping lane say, and for that reason alone, perhaps we'll have to reconsider it. The twin engine approach is probably beyond my pocket at the moment, but a pair of 50s might be the best solution of all. I'm sure it would be juicier though...
The twin engine approach will be more expensive, heavier, less powerful & dearer to service than a single main engine & aux. It will be of no use unless one of the pair can plane the boat on it"s own & in my experience this won"t be the case.
If for example the hull was rated to carry twin 40hp"s & 40hp was enough to plane the boat the likelyhood is that should the need arise the single 40 would not plane the boat as it will have been propped as a pair & the prop pitch will be to high. Unless you want to change the prop at sea all you will succeed in doing is get displacement speed whilst burning a lot more fuel than say a 5hp aux.
I have 2 friends with twin set ups & neither can plane on a single engine. Although theoretically one engine is powerful enough to plane their boats in both cases the prop pitch stops them.

headlight
 

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The prop is on a spline, the nut isn't. Without the locking mechanism, as soon as the nut loosened very slightly, engaging reverse would spin the nut off in seconds. The shaft would be spinning anti-clockwise and the nut would be undone by centrifugal force and/or the drag against the water.

Also sounds to me as thought the nut wasn't fully tightened and locked after the service.
With a Right Hand prop, the nut would spin off in forward, but the nut would have to be loose too start with. Then as soon as reverse was selected the prop would pull it's self back and off.
 

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Discussion Starter · #11 ·
Unless the prop had been tampered with it's the only real explanation...

Main thing is, no one was hurt this time. Thanks for all your input chaps.
 

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Unless the prop had been tampered with it's the only real explanation...

I thought that,it is a possibility.What model is the outboard and where is the boat stored (driveway ? compound ? storage ?).Some toerag could of been after your prop,pin out or lock tabs back nut 1/2 off then bottled it or got disturbed and left it :g:.

Ian
 

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Unless the prop had been tampered with it's the only real explanation...

I thought that,it is a possibility.What model is the outboard and where is the boat stored (driveway ? compound ? storage ?).Some toerag could of been after your prop,pin out or lock tabs back nut 1/2 off then bottled it or got disturbed and left it :g:.

Ian
My thoughts also, given the time the mechanic took to explain the torque. Most thefts are rekkied prior to the actual evant which takes place at a later time. Keep your trust in the chap, if he was at fault (seems unlikely considering your recolection of conversation) then he sure would make sure it would never happen again. We all make mistakes. I for one am not immune
 

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Discussion Starter · #14 ·
Thought I'd update you all, as I just had a chat with another boat owner in the same yard. It turns out that the S/S prop was taken from his Warrior, round about the time we had ours fall off at sea. It looks like our fears that it had been tampered with have been confirmed-it's just too much of a coincidence for it not to be related. Looks like they took his and then started on ours, perhpas getting disturbed before they had chance to finish the job.

In a way I'm glad to know neither myself nor the mechanic were at fault, but, had events taken a nastier turn at sea and we hadn't come back, there would have been a potential case of manslaughter, had it ever come to light of course.

It's sad but it seems everything has to be bolted down or removed these days and the fact that folk are prepared to endanger lives by loosening someone's prop just beggars belief.
 
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