Gori Prop Problem

[svrevelations]

Originally Posted by Zanshin

You've revived this 5-year-old thread from a dusty grave!

I had a Gori on my previous boat and was actually quite happy with it. Greasing and inspection and replacing Zincs was all I needed to do and the overdrive functionality was great.

I was also very happy with my Gori props - until the one fell off for no reason. I only realized that the propeller was missing when we were in close proximity to other boats within the moorings - it could have led to a lot of additional damages. But it was when we engaged Gori about the problem, their reaction and silly blind responses that made us realize that we would be far safer with another manufacturer. At about US$5000 for the Gori props, anybody would be very pissed! And rightfully, so would you if this ever happens to you.

[Zanshin]

C - I used an underwater grease on the gears of the Gori, making the transition from reverse to forward quicker. I did this every time I had the boat out of the water. I'm fairly confident that it wasn't necessary but I did it anyway.

[Jurassicrock]

It's 2015 and guess what. My gori prop has come off. Been fine for 7 years. About three weeks ago had a metallic scraping. If the prop is keyed then it can only come off if the retaining nut comes unscrewed. My prop was fitted to a new shaft by the supplier. Two weeks ago same metallic scraping then no drive. Prop lost. It is my opinion there may be a design flaw and I will be notifying Gori. I fitted the internal split shaft coupler to the prop shaft but added a recess flat top the shaft and an M8 Alan socket screw through oneside of the coupler to stop the prop shaft dropping out. Kept the screw in place with tie wrap. Still fine.
So why have I lost my prop. Has the shaft sheared,by metal fatigue. Grub screw failure.
Seems rather small for the job. Have tried to find details on just how prop is fitted but not complete yet. If I find any more I will add it. One final point. It is in my opinion OK to express experiences with suppliers but agree that is where it must stop as opinion on such matters as have been expressed are certainly bordering on the libelous.

[Zanshin]

Far be it from me to defend a manufacturer, but...

It sounds like after 7 uneventful years with a Gori you have had the shaft replaced, and within two weeks of that happening the prop has fallen off the shaft. Yet you've decided that the prop manufacturer is at fault. I have to admit that I have trouble following your reasoning and I feel that Gori might have that problem as well.

[fstbttms]

Originally Posted by Zanshin

It sounds like after 7 uneventful years with a Gori you have had the shaft replaced, and within two weeks of that happening the prop has fallen off the shaft. Yet you've decided that the prop manufacturer is at fault. I have to admit that I have trouble following your reasoning and I feel that Gori might have that problem as well.

Agreed. How is any of this the fault of the prop manufacturer? Plus, I am always suspicious when the first (and in this case, only) post by any forum user is one that slams a product or service provider.

[nauticalnomad]

I had a gori prop that was 2 years old fly off from the rubber vulcanized bit that joins the inside shaft joiner to the outside propeller housing..
It just sheared off coming into berth.
Gori explained that this does not happen and they have not heard of it before and they will sell me a new one at cost price due to the warranty being not long out.

After accepting I then do some research and find on and offline from various people and fellow marine engineers that this is a common issue with Gori folding propellors....
I no longer have the boat. My new boat has a fixed propeller. I would not buy a folding prop..

[Jurassicrock]

Originally Posted by Zanshin

Far be it from me to defend a manufacturer, but...

It sounds like after 7 uneventful years with a Gori you have had the shaft replaced, and within two weeks of that happening the prop has fallen off the shaft. Yet you've decided that the prop manufacturer is at fault. I have to admit that I have trouble following your reasoning and I feel that Gori might have that problem as well.

.

I regret, my initial statement seems to be poorly written. The situation was that the prop and new propshaft were married together 7 years ago by a supplier from Poole so it was professionally mounted. Until I get the boat out I wont be able to tell if the retaining nut unscrewed or the shaft sheared on the thread. The threaded section seems very short. I make no accusations against Gori or the supplier. To replace to prop will be in excess of £600 pounds and I may need a new shaft. The purpose of my initial post was to show that there may well be a design issue with the mounting and to support those others who have lost their props. Personally I like the Gori prop. I have tried to find out as others have on just how it is mounted. I see the grub screw on the main hub that pins the retaining nut as a possible area of weakness.
I have mailed Steel Team, who I believe designed the prop for Gori and have asked them specifc questions wrt materal of key, the Torque requirement of the retaining nut ect.
The only othe thing I have to offer is that last year I heard a larg metalic bang whilst under power traversing Weymouth Bay. No marks on boat or prop. It could well be that it might have been the point of something breaking on the shaft. The prop would have stayed in place due to frictional forces present. All speculation but some analysis has to be done.
I have not decided that the manufacturer is at fault but I have proposed to them that there may be a design flaw/weakness in its mounting.

Without constructive opinion how can the manufacturer improve on its design. Im not intending to make a claim so my reasons are honourable.
Suggest we should aim to work together to improve where we can the equipment we use.

[Keen Sailor NL]

I have read through the entire thread, because I just lost my 2-blade Gori folding prop after 5 seasons of operation. I did not hear or feel the loss of the prop... I can only surmise that the allen srew locking the shaft nut would have backed out and allowed the shaft nut to gradually back out... or probably that the hardness of the steel of the shaft nut may be less than that of the allen lock/set screw and the shaft nut hexagonal section would have been gouged and worn to then allow the shaft nut to back out. I did not hear or feel any additional shaft vibrations lately. I did not hit anything, my prop being tucked in between the keel and the rudder...

I'll see if insurance covers such a loss... I am considering Flexofold... What's the scoop on Flexofold these days....?

Thanks,

Hubert

[Cheechako]

Max Prop. .....proven, proven, proven!

[Jurassicrock]

Hi Hubert,
It is clear to me that folding props have issues. I will keep this thread going as I just dismantled my old folding prop which has been on the boat since at least 1986(When I bought it).

Some folding props(Two blade) have rubber shock pads to reduce the shock when the blades come out in forward. My twin blade Gori did not neither did the old folding prop but on the old one the impact damage is clearly visible. The condition of the barrel nut was poor suffering from corrosion faliure at the hex head but the barrel part was OK. You need a lot of heat to free up parts.

In conclusion this type of prop should have regular maintenance checks. I am building up information of photos and will pop them in a Web Site and let you have the reference.

Brendan.

[fstbttms]

Originally Posted by Jurassicrock

It is clear to me that folding props have issues.

As someone who has spent the last two decades earning their living maintaining all manner props (be they fixed, folding or feathering) on pleasure craft, I disagree with the above statement wholeheartedly. I have preformed over in-water 25,000 service events and have never found folding props to be more prone to problems than any other type. Yes, they have moving parts that wear and therefore require maintenance. But your inference that this type of prop is somehow inferior to others is simply not what my professional experience has taught me about them.

[Jurassicrock]

Thank you for your input on this issue. My intention is to try to find out why people like myself and other have lost their folding props. I have no intention to question anyones professional judgement but the threads about people losing them and my own experience seems to show otherwise. Maybe, you, in your twenty years know of owners of folding props who have lost them and the possible reason for failure. I have not said that a folding prop is inferior to any other prop. What I dont wont to do is to fit something that I may worry about.
This morning in the fog and drizzle I went searching for the lost prop wth a Diver but no luck.
I shall be contacting the supplier later to see if he can supply information on the Taper for a Gori 12/14 inch prop and the length of thread they normally put on the shaft for 25mm dia because mine seems very short and I believe it has sheared.
I agree with you that any propellor with intergral moving parts requires maintenance and my Diver friend takes off his Volvo prop every year. Strips it down,cleans it etc. I did check mine at the start of the season. No impact damage. The blades did have some minor wear on the swivel pins but not excessive when compared with others. Cleaned up the gears and greased them. Its the shock issue and the retaining issue I have concerns about. I dont want to go to sea with concerns that I may loose it again. So if you have any information on failure modes would you like to share them with the community.

regards
Jurassicrock

[fstbttms]

Not sure how a broken shaft end equates to inherent, chronic problems with folding props. Again, folders are no more prone to loss than any other type. Every lost folder that I have come across (and I can remember three of them) can be traced to improper installation or corrosion issues.

[Yury]

I don't want to comment anything, just look what the seller AB Marine replied to me and what information he asked from me...

"We can ship the Shaft Shark by US Intl priority mail. To order, Please provide the ship to address, priority(UPS ground/red/3 day, etc.), your full credit card info(Visa or MasterCard only), including card #, expiry date, name on the card, card bill to address with zip/postal code & the 3 digit security verification # from the back of the card. Ican also send you our wire transfer instructions."

[bethsail]

I have a new to me Tartan 4100 and just lost a gori prop in Cape Cod while leaving a mooring. Didn’t run over anything etc. previous owner lost two Goris on this boat in 16 years. I’ve been sailing for thirty years, owned 7 boats with both fixed and folding props, (never a gori until now ) and Have never lost a prop. The boat speed and boat handling with the Gori, especially in reverse, are second to none. While I will buy another one for racing, I am going to carry a backup fixed prop and prop kit. It seems that these props have a tendency to fall off much more so than other types of props. Not bashing them but there is definitely an issue.