Gori Prop Problem

[hellosailor]

Kai Nui-
Your comments for some reason made me think there could be a simple reason behind these failures, assuming for the moment there is some truth in the accounts of them.
If the Gori installation involves a plastic part (rather than the conventional all-metal) and the installation involves BOLTING a bolt over that part...
This sounds an awful lot like the part could fail from improper torquing of the bolt, causing it to over-compress and fail. One of those simple real-world events that cause massive failures because folks (either the vendor or the installers) just forget to mention the use of a torque wrench is sometimes not optional.

I mention this because of the similarity to a common torque problem in the auto business: Wheel lug nuts. Here in the US, most shops put on lug nuts with air wrenches, which are usually preset to "Gorilla" and left there. Well, some years ago a couple of car makers traced a number of brake and wheel failures to over-torqued lug nuts, caused by the same authorized mechanics who used those gorilla guns every day.

By now every auto maker has documented this and even the indy shops try to make sure the torque is right by using torque-matched color-coded wrench fittings. But still...every year when my car is inspected, no matter who inspects it, they torque the lug nuts to over 125# when the spec is only 75#. And they *swear* there's nothing wrong because they do it the same way to every car.

Uh-huh.

Could just be something as simple and elusive with the Gori props, a poorly documented procedure "versus" an uncommon construction method. Of course, with Gori not posting any instructions, that's all just a guesstimate of one way that "all" parties could be "right". And wrong, at the same time.

Hellosailor, great point. That is one of the reasons I suggested Gary email the vendor. I would be very interested in their input on this.
Having worked in shops for many years, and knowing the proper way to install lugnuts (I was tought by a screaming foreman), I agree this is a common issue with torque sensitive connections. It alos is a great example of the issue. A prudent mechanic would be aware of the issue, and a prudent mfg would write their manual for dummies. If both sides failed, the product is fine, but both sides need to be aware that they share some responsibility. Listening to only one side does not give us that information. If Gori is contacted, and does not not respond, that is, in my mind, an indication of poor customer service, and would give me pause about buying their product regardless of quality. If they respond, and even if they blame it on the installation, I would consider that a clear indication that they are concerned about customer satisfaction.

[hellosailor]

A prudent mechanic?

I don't think I've seen any that have been certified prudent, yet.<G>

Guess I'll have to look for one with extensive marine aviation experience, and then rob a bank to pay him.

Memo: First, buy black ski mask.<G>

[senormechanico]

FWIW, I have a 2 blade Gori on my Dragonfly 1000 and it hasn't fallen off.
So there!

Steve B.

and it's been on there for 11 years!!!

[Alan Wheeler]

You see folks! so they are not ALL bad.
Steve, can YOU please explain to me, how are these things fitted. I have never seen the way they are attached and am very curiuose. Could you elaborate a little on what you need to do to fit them correctly and if possible, what you think may have gone wrong in the case of the original poster. Thanks heaps.

[senormechanico]

First of all, I bought the boat used, and the prop hasn't been off the shaft since I owned it. I did remove the shaft once for a different problem, and I also replaced the blades because of wear/damage to the gears which was there when I bought the boat. (I don't know how that happened).

When I replaced the blades, for each blade I undid an allen screw which locked in place a second allen screw. This allowed the removal of a short fat SS pin which is the hinge for the prop blade. After removing both blades and the integral gear on each one, this exposes the shaft nut. I didn't go any farther, but it looked to me like a normal type installation with a locknut or similar, and a tapered shaft with a key. I don't know for sure.


Steve B.

[hellosailor]

So there are three possible failure modes?
1-That the standard locking nut on the prop shaft let go, or
2-That the plastic part between the hub and the rest of the prop failed, or
3-That multiple allen screws came out (Loctite is your friend<G>) allowing a stainless pin to let go from a blade

In which case, two failure modes where the whole prop would be gone, and a third which would cause a bit of a failure. I could see assembly problems, material defects, galvanic problems and other ways these failure modes could begin.

Not to mention, attacks by giant Kraken, Narwhals, or intelligence agencies. (Can't rule that out, look what happened to Rainbow Warrior.)

Does that seem right?

And no one has been able to dig up installation instructions or diagrams? There's been no reply from Gori?

[Alan Wheeler]

Not sure if anyone has asked Gori. Gord, you have any contacts there???
Sounds to me that this prop is pretty well attached and no differently to any other way any other prop can be attached. Sounds to me the "mechanic" fellow didn't know what he was doing and maybe that fellow is the one to blame.
I cam across a prop the other day, a mates boat was hualed out and I had volunteered to polish the prop for him. Well we found it very loose. On removale, we found the Key was made from a bronze, but must have been just ever so slightly a different make up of metal to that of the prop. So the key had all but gone and how on earth the prop was not simply spinning around allowing him to go no where beats me.

[senormechanico]

[/quote]
And no one has been able to dig up installation instructions or diagrams? There's been no reply from Gori?[/quote]



Well now that I think of it, I DO have the instruction sheet. It's in 4 languages, too. There's an exploded diagram as well. I haven't figured out how to post a pic, but it's pretty basic. It's just a hub, a couple of blades, a nut a couple of ss pins and some allen screws.

--------------
Installation Instructions:


1. Take the propeller apart.

2. Check that the hub fits the cone of the shaft and ensure proper seating without key interference.

3. Mount the hub on the shaft and tighten the nut (4) very tight.

4. Mount and tighten the allen screw (5). Secure the allen screw by smearing it and the threaded hole with the enclosed locking glue, e.g. loctite 242.

5. Grease the moving parts of the blades with a water resistant grease. Mount the blades (2) and the steel pins (3). Watch that the marks 1 and 2 are opposite each other.

6. Smear the allen screws (6) and (7) and the threaded holes with the enclosed locking glue. Tighten the allen screws (6) very hard. Countertighten the allen screws (7).

7. Check that the blades move freely from closed to open position.

8. Mount a zinc anode on your shaft.

So, we have a rather sparten account of the installation instructions. I notice "very tight" and "LockTite" in these instructions. No mention of torque specs. No mention of a plastic part.
Gary, was your prop locktited? And, with which Locktite? I see mention of 242, but in the same sentence, it mentions the "enclosed locking glue" Did your prop come with "locking glue"? Or did you have to purchase something seperately?
Also, is there any sort of accomodation for a lock pin on the assembly?

As per our guidelines, I have contacted Gori with an invitation to review and respond to this thread. Here is the content of the email:

Dear Sir/Madam,
My name is (Kai Nui). I am a site administrator at Cruisersforum.com.
Recently, one of our members related a negative exprerience with your product, and one of your vendors. In the interest of fairness, we are requesting that you review the concern, and respond as you feel is appropriate.
The following is a link to the posting. I ask that you read the concerns, and either sign up to post a reply, or email a response directly to me, and I will post it for you.

http://www.cruisersforum.com/forums/...?t=5537&page=1

It is our goal to provide a positive and usefull service to all cruisers, and as such we feel your participation in this discussion would be beneficial to all parties.

If the response is emailed to me, I will post it here.

[wind rose ll]

Not that one design is better than the other but the primary reason, as l see it, for purchasing a variable pitch prop is to assist in reversing and to try to eliminate the walk of the prop.
Personally l use reverse more as a brake and the inherant walk is used advantagously to asist in close quarter turning.
l sail a full keel Bayfield 36 and when new to the boat was very apprehensive about reversing...like most things the more you practice the easier it becomes....till at this point it is no longer an issue or concern.
Besides which, it will do you no good if under sail or the engine fails.

[yotphix]

On the gori site they mention that they make a prop for saildrives with a rubber dampener. Perhaps this is the mysterious plastic part. No need for the dampener on a regular engine driven shaft.

Well, despite the concerns, I decided a Gori prop was the right solution for my boat. I purchased one. Unfortunately, when I attempted to install it, the one dimension that I was not asked for, and did not consider, was the distance between the strut, and the rudder. The prop would not work. No problem, go to plan B, and buy a feathering prop. Unfortunately, before I could ship the Gori back (I still can not get an email response out of them), the boat leaked, and the box was damaged. Understanding that thi could be an issue, I spoke with the Gori rep at Stricktly Sail in Oakland, asking if he could give me any input. His response, I can only believe is SOP for Gori's customer service based on my experience to date, was, "I don't have time to discuss it. Call the store."
I understand these events are a busy time for vendors, and, quite frankly, hated to bother the guy, but since I was the only person within 20 feet of his booth, it seems he could have maybe taken a moment to understand my concern. I will be sending my prop back to Gori, and paying whatever restocking fee they charge, and I will not, under any circumstances, be using, or promoting their product. Not because it is a bad product, but because I find this kind of poor customer service completely unacceptable.

[S/V Elusive]

Scott - all you had to do was ask ... I've had some luck dealing with vendors at the Oakland Boat Show.