Gori or Flex-O-Fold

CCHer

.
Jul 7, 2010
230
Beneteau 37 Cranes Creek, VA
Going to a folding prop for next season. I like the folders over the feathering for my purposes and these two seem to be the leading candidates based on my research. Most likely need a three blade for my sized boat and engine. Hearing forum members opinions and experiences on these (or other brands) would be very welcome. 2 to 3 boat bucks makes for a big decision!
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Re: Gori or Foldoflex

Harry, I bought and like the Gori. Saw their display at a Beneteau Rendezvous. I like that (the 2-blade I bought) the 'meat'/width of the blade is out at the ends, not tulip-shaped like most. They have an on-line calculator, I believe.
 
Sep 8, 2013
71
Beneteau Oceanis 45 Rock Hall, MD
I'm going to order the Flex-o-fold for next season. I've already done the research and have the size and pitch selected. Also had a folder been provided by Beneteau from the factory it would have been the Flex-o-fold.
 

DougM

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Jul 24, 2005
2,195
Beneteau 323 Manistee, MI
I am using a 2 blade Gori and am happy with it. Better reverse bite than the stock fixed 2 blade. My primary reason for getting it was because Yanmar discourages locking the prop in gear, and I didn't like the rotation noise when the gearbox was in neutral.
 

CarlN

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Jan 4, 2009
578
Ketch 55 Bristol, RI
I've had both Gori and Flexofold (three blades) on separate boats. The trick with both is getting the right size/pitch. Try to find an identical boat who is happy with their size.

I would go with Flexofold because:

The Gori opened with more of a "bang" than the Flexofold. I worried about drive train stress.

If your Gori prop is correctly sized then you are overpropped when in "overdrive". This can hurt your engine and possibly void your warranty (although I haven't heard of Yanmar not liking the Gori). In my boat with the Gori, my top RPM was 300 below what it should be when in overdrive so I didn't use it. But without overdrive the boat felt a little underpropped.

My Gori was more troubled by barnacle growth than the Flexofold. I don't understand this and it may be an unfair comparison. These were different boats so something else may have been the cause. Several times the Gori couldn't open because of barnacles in the gears.

Both the Gori and Flexofold don't spin the shaft when closed.
 

Johnb

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Jan 22, 2008
1,302
Hunter 37-cutter Richmond CA
Re: Gori or Foldoflex

I have been happy with my Flex-O-Fold for 7 years now. The sailing performance was improved and the whole issue of in gear/spinning goes away.

One thing - if you just shut the engine down in neutral whilst sailing the prop will keep turning. It seems the centrifugal force from spinning is enough to keep the blades open and thus keep the prop spinning.

I don't know if it is the best, I have nothing to compare it to.
 
Sep 8, 2013
71
Beneteau Oceanis 45 Rock Hall, MD
I think most engine manufacturers are worried about over propping their engines if only for the loads at wide open throttle. Unfortunately with a fixed pitch prop this leaves a big sag in the load curve in the mid RPM range. At the RPM most of us would prefer cruising, the engine is under a lighter load than is ideal. I'm new to this sailing thing and displacement hulls, but I wish I had a dime for every person that has told me "Yanmars like to be run at higher RPM's". I'll bet this has to do with soot buildup in the lighter loaded RPM range because of the lower cylinder pressures and temperatures.

In my case I was told that the target RPM during sea trials for the OC45 and the 4JH5E was 3150, right about where I am at, a full 150 above the max rated 3000. This may provide a margin of safety regarding engine loading for the manufacturer but does the owner a great disservice as far as how it will actually be operated. For example If I added another inch of pitch I would probably drop down to about 2900. This should be well within the acceptable range of operation, and make for a more comfortable cruising experience. Instead I'm read the script of fear with regards to the manufacturer and warranty when considering a prop change. It's BS as far as I'm concerned.

I was not aware the Gori's had an overdrive feature, but it makes a lot of sense. My question is does it not drop out at higher RPM and loads? In which case the loading would be a non-issue. I also considered the Autoprop but the tests I read showed only a marginal improvement in the mid cruise RPM range versus a Flex-o-fold, with inferior performance in other areas, specifically slightly more drag while sailing. Since the primary purpose of my boat is sailing and not motoring I am leaning toward the Flex-o-fold, and it's about 2K cheaper.
 

DougM

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Jul 24, 2005
2,195
Beneteau 323 Manistee, MI
I seem to recall reading something about an "overdrive" feature awhile ago but I am not certain that it pertained to a Gori prop. Unless they have changed a design I don't know how the prop could change pitch to an overdriven configuration.

I have always been curious as to why people are so overly concerned about maximum RPM numbers.. A displacement hull will only go so fast. If it gets there at 2/3 throttle, more isn't going to make it go any faster anyway. I have been of the opinion, right or wrong, that it was easier on engine not to run wide open anyway. When I had powerboats, I would change props to higher pitch for more pulling power, and to lower pitch to gain more speed.
 

Mikem

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Dec 20, 2009
764
Hunter 466 Bremerton
Re: Gori or Foldoflex

I read all the studies and concluded that the flex-o-fold would be the best for my H466. I gained .2kt under power to 8.8 (WOT) and .7kt under sail. I can tell no difference in reverse from my previous fixed three blade.
 

CarlN

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Jan 4, 2009
578
Ketch 55 Bristol, RI
The Gori "overdrive" is engaged by going astern and then quickly going into forward gear without letting the blades close. This reverses the side of the blade that is "leading" and is designed to give 20% more pitch to the propeller.

The pitch change is across all RPM.
 
Oct 3, 2008
313
Beneteau 393 Chesapeake Bay
The Gori "overdrive" is engaged by going astern and then quickly going into forward gear without letting the blades close. This reverses the side of the blade that is "leading" and is designed to give 20% more pitch to the propeller.

The pitch change is across all RPM.
This is consistent with my experience on my boat with the Gori, as well as what their own literature says. I have a B393 with Yanmar 4jh3e engine (54hp). I have had no problems so far in 4 years (knock on wood). When I engage overdrive, I get the same boat speed for 20% fewer rpms, or a higher boat speed for a given rpm (up to a point when hull speed limits further speed increases). So in my case, I can do 7.5 kts or higher without revving the engine too much. The 54hp for my boat is pretty substantial, so the engine is not stressed much at all.

I have had good sailing performance with the Gori. About 0.5 to 1.0 kts better in light to medium air, and I can point a bit higher. I don't think that Gori is alone in this improvement; most folding props will do similar.

Annual maintenance is during haul out. I just clean the prop, grease the gears, and inspect. Also have a diver a couple of times a season. Seems pretty good so far.
 

CCHer

.
Jul 7, 2010
230
Beneteau 37 Cranes Creek, VA
Good discussion and thanks. I've been thinking that the Gori with overdrive might be adding a complication that has marginal benefit. Paul indicates otherwise though I wonder if the normal pitch is then a bit underpropped. Anyway, I'll be putting together some question for the sales people. They have winter discounts going right now.
 
Sep 8, 2013
71
Beneteau Oceanis 45 Rock Hall, MD
Winter discounts?:) Please share. I'm not sure I'm being offered a discount on a Flex-o-fold, but it is December now.
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Good discussion and thanks. I've been thinking that the Gori with overdrive might be adding a complication that has marginal benefit. Paul indicates otherwise though I wonder if the normal pitch is then a bit underpropped. Anyway, I'll be putting together some question for the sales people. They have winter discounts going right now.
Just to point out, not all Goris have overdrive.
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
I think most engine manufacturers are worried about over propping their engines if only for the loads at wide open throttle. Unfortunately with a fixed pitch prop this leaves a big sag in the load curve in the mid RPM range. At the RPM most of us would prefer cruising, the engine is under a lighter load than is ideal. I'm new to this sailing thing and displacement hulls, but I wish I had a dime for every person that has told me "Yanmars like to be run at higher RPM's". I'll bet this has to do with soot buildup in the lighter loaded RPM range because of the lower cylinder pressures and temperatures.

In my case I was told that the target RPM during sea trials for the OC45 and the 4JH5E was 3150, right about where I am at, a full 150 above the max rated 3000. This may provide a margin of safety regarding engine loading for the manufacturer but does the owner a great disservice as far as how it will actually be operated. For example If I added another inch of pitch I would probably drop down to about 2900. This should be well within the acceptable range of operation, and make for a more comfortable cruising experience. Instead I'm read the script of fear with regards to the manufacturer and warranty when considering a prop change. It's BS as far as I'm concerned.

I was not aware the Gori's had an overdrive feature, but it makes a lot of sense. My question is does it not drop out at higher RPM and loads? In which case the loading would be a non-issue. I also considered the Autoprop but the tests I read showed only a marginal improvement in the mid cruise RPM range versus a Flex-o-fold, with inferior performance in other areas, specifically slightly more drag while sailing. Since the primary purpose of my boat is sailing and not motoring I am leaning toward the Flex-o-fold, and it's about 2K cheaper.
I would encourage you to speak with the technical folks at Mack Boring regarding your Yanmar and prop pitch. Over-pitching a yanmar prop effects all portions of the power curve /fuel mix ratio and contributes to the carbon build from overly rich mixes. Don't think you have the max engine rpm correct either. These engines like to spin up, but you can run them efficiently at less than cruise, or max rpm. You just don't want to do so with an over-pitched propeller. The ability to make max rpm is a test to make sure your propeller is properly pitched. Can't make it, you are over-pitched. You might want to consider an adjustable pitch prop for maximum tuning.
 
Sep 8, 2013
71
Beneteau Oceanis 45 Rock Hall, MD
I would encourage you to speak with the technical folks at Mack Boring regarding your Yanmar and prop pitch. Over-pitching a yanmar prop effects all portions of the power curve /fuel mix ratio and contributes to the carbon build from overly rich mixes. Don't think you have the max engine rpm correct either. These engines like to spin up, but you can run them efficiently at less than cruise, or max rpm. You just don't want to do so with an over-pitched propeller. The ability to make max rpm is a test to make sure your propeller is properly pitched. Can't make it, you are over-pitched. You might want to consider an adjustable pitch prop for maximum tuning.
3000 RPM is MAX RPM in the manual for the 4JH5E, with a max sustained operation of 2900. I've only ever operated at these speeds to confirm what my max is. The manufacturer shoots for something higher. My normal operating range is 2100-2600. Ideally I would like to target 2100 always. An Autoprop can achieve this comfortably and seems to do so with Yanmars acceptance, yielding speeds nearer what the fixed prop would need 2500 to accomplish.

I understand the concept of using Max RPM to confirm prop sizing, I just don't agree with the high target. The Turbo Charged version is rated at 3600 RPM so indeed I'm sure 3000 is no problem mechanically. I guess the question is what is over-pitched? Is in fact being able to reach max the true measure or is it something slightly less. As for fuel mixture in a diesel, it will probably be at it's richest under max torque load for a given RPM. On a boat with a displacement hull and fixed pitch prop this will likely coincide with max
RPM, a region we are not likely to operate. I suppose there are folks out there that will run at wide open throttle without much thought for the engine, and those are the ones likely driving the logic.
 

CarlN

.
Jan 4, 2009
578
Ketch 55 Bristol, RI
I remember some years ago there were complaints that Gori was sizing props based on the overdrive configuration. There were complaints that this resulted in poor performance when not in overdrive.

Also, I've heard of multiple situations where a new prop vibrated badly. This seemed to come from the interaction of the prop with the nearby hull. While a larger diameter prop is an obvious reason, it seems that different designs but the same diameter can still cause troubles. Propeller manufacturers specify a "minimum tip clearance" as a percentage of the propeller diameter (like 15%) but in one case the vibration was quite severe even with double the recommended clearance.

So many factors effect propeller performance that talking to someone with the same boat/prop combination you're considering is the only way to be confident of the right size and pitch.