3 blade Max prop vs 3 blade fixed?

[Stumble]

Originally Posted by a64pilot

I use a cheap gun with a rubber hose as I'm afraid of snapping off the zirc fitting, it has survived a couple of years with nothing more than being rinsed off well and put it a trash bag.
I'd like however to find some 5mm SS zircs so that I can leave them in and not be taking out the internal wrenching plugs everytime.
The grease Autoprop specifies can be found on Amazon.com, it is a type of wheel bearing grease I believe.

As far as zincs, I believe if it is metal and connected electrically to your engine, you had better have a zinc on it, SS or not.
I don't know if SS is "better" than bronze or not, but I saw on EWOL's website that they have Titanium blades available for those who feel so inclined? Would cut down on weight considerably, I believe weight on these complex props is an issue with the driveline.

If it's metal it needs a zinc. A 304-316 connection can cause corrosion, not much to be sure but enough. Heck a stainless rod that penetrates the waters surface can corrode itself.

I do have a concern with a titanium blade though. As much as I like titanium stuff, it isn't terribly stiff, so if it isn't designed well it could have a lot of flex. The upside is that it isn't bad for the metal, the downside is it may rob performance.

[EWOL Props]

You are right, all stainless steels can be subject to corrosion, although much less than bronze alloys used for all other props.
By the way we mostly use Super-Duplex alloys which represents the highest level of corrosion resistance in steels, these alloys are used typically on offshore oil platforms on flanges where corrosion would represent a big risk.
In any case we suggest to have anyway zinc anodes installed (although we can supply a stainless steel nose to replace the anode).

As for Titanium alloys, the advantages are mostly on larger blades, where weight can be important and also inertia on rotation.
Titanium alloys have high strength, low weight and high corrosion resistance.

You can write me at info@ewoltech.com if you want to know more on that

Originally Posted by Stumble

If it's metal it needs a zinc. A 304-316 connection can cause corrosion, not much to be sure but enough. Heck a stainless rod that penetrates the waters surface can corrode itself.

I do have a concern with a titanium blade though. As much as I like titanium stuff, it isn't terribly stiff, so if it isn't designed well it could have a lot of flex. The upside is that it isn't bad for the metal, the downside is it may rob performance.

[jtsailjt]

Originally Posted by J Clark H356

I just got my 2003 MaxProp back from PYI reconditioning and will install this week. Cost was $731 to recondition plus shipping. I got new hub, cone gear, reconditioned blades and whatever else they recommended. After discussion with them, we also had them change the pitch from 22 to 20. That will give me 300 more RPM and I will be at my full rated 3600 versus 3400 RPM from my original 2003 installation. I have 1271 hours on the engine and 7620 NM. Although my fuel economy was good before, I think this will improve speed at same cruise setting and reduce fuel use some.

I can back my boat very well and really like the MaxProp.

Jerome from PYI was excellent to work with.

I'm looking forward to this coming weekend to see what happens.


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You might want to consider leaving the prop pitch where it is. Being "overpitched" by 200 RPM isn't going to hurt your engine when you so rarely run it at WOT and at normal cruise settings it is helping your engine run at a slightly higher temp which is a good thing for a diesel. I have a max prop and echo your appreciation of both the prop itself and the support the company offers.

But there are two schools of thought on proper prop pitch and there are some who say it's better for the engine to have it pitched about as you say it was before your reconditioning as opposed to being able to turn max RPM while in gear. I'm not sure how decreasing the pitch will help your fuel economy because it's like shifting your car into a slightly lower gear so you have to run it a little faster to turn the prop at the same speed. It won't increase your speed at the same cruise setting, it will decrease it. If you were grossly over propped, I could see that rationale, but I think what you are planning is more likely to very slightly hurt your fuel economy as well as decrease your speed at the same "cruising RPM" setting.

There is a very good discussion of pro's and con's of prop pitch who know a lot more than I do about it over at Attainable Adventure Cruising if you're interested.

One of the nice things about maxprops is we can always try different settings and change it back if we don't get the desired results. Good luck.

[EWOL Props]

Fully agree with you jtsailjt, I would have left the Max-Prop at 22°.
Decreasing the angle to 20° will reduce cruising speed at same rpm and increase fuel consumption.

[Cheechako]

Originally Posted by TacomaSailor

Clumsy use of any tool will result in problems and undesirable results!

22-years experience with a 40' / 23,000 pound long-keel boat and another 3-years with a 42' fin keel raceboat both with an 18" Maxprop. That experience tells me that Prop Walk is a huge advantage. I've docked both the boats and picked up moorings in horrible crowded conditions in cross winds and tailwinds from the North end of Vancouver Island to SW mainland Mexico. I'd never want a boat without a Maxprop or similar prop that provides full thrust in reverse.

I've learned:

- Use very little throttle in reverse because it is not needed

- Use short spurts of higher power in reverse to swing the boat without inducing sternward motion

- Use reverse throttle to gain momentum then put the transmission in neutral and steer the boat with it's momentum

- plan all your maneuvers to take advantage of Prop Walk

- Practise, Practise, Practise! I used to go out into open water and throw a life ring in. Then I'd spend hours backing up to the life ring from all wind and current angles. I learned how the boat and prop worked together in a wide variety of conditions.

- I learned I can easily back in a perfectly straight line at 6 knots and with a firm grip on the wheel I could precisely steer anywhere I wanted.

Yep. As I said earlier just get your boat moving in reverse slowly , not by gunning it. you gradually get moving well in reverse and don't need much reverse prop at all. If you gun your boat in reverse any prop will walk.

[groundtackle]

I just cleaned up my two blade max prop. It works great and I love the prop walk. I try to avoid situations where I need to make the stern go to port in reverse but I can turn in circles in the other direction while making essentially no headway at all which proves very useful.
My max is an older one with no built in zinc that I think newer ones incorporate. It relies solely on the shaft zinc for protection. It's badly pitted and I think I'm going to have to replace it in a few years. Or someone mentioned restoring it? Can new metal be added to the pitted eroded areas effectively returning it to great condition? At what cost? Any recommendations for who is good at this process? The gears and inner workings appear in great shape (I've had it apart a couple of times)
Or alternately should I just think about replacing it in the coming years ($3500ish....ouch) and getting the benefit of the incorporated zincs.

Thanks
Nick


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[J Clark H356]

Originally Posted by jtsailjt

You might want to consider leaving the prop pitch where it is. Being "overpitched" by 200 RPM isn't going to hurt your engine when you so rarely run it at WOT and at normal cruise settings it is helping your engine run at a slightly higher temp which is a good thing for a diesel. I have a max prop and echo your appreciation of both the prop itself and the support the company offers.



But there are two schools of thought on proper prop pitch and there are some who say it's better for the engine to have it pitched about as you say it was before your reconditioning as opposed to being able to turn max RPM while in gear. I'm not sure how decreasing the pitch will help your fuel economy because it's like shifting your car into a slightly lower gear so you have to run it a little faster to turn the prop at the same speed. It won't increase your speed at the same cruise setting, it will decrease it. If you were grossly over propped, I could see that rationale, but I think what you are planning is more likely to very slightly hurt your fuel economy as well as decrease your speed at the same "cruising RPM" setting.



There is a very good discussion of pro's and con's of prop pitch who know a lot more than I do about it over at Attainable Adventure Cruising if you're interested.



One of the nice things about maxprops is we can always try different settings and change it back if we don't get the desired results. Good luck.

I just put my prop back on yesterday and set it at 20 versus the original 22 degrees. I'm going to try it for a couple of tanks of fuel and see how it affects me. I was only able to get to 7.2 knots versus hull speed of 7.4 where I was. I can live with a little more fuel burn if my speed will increase. When going to Florida down the TennTom a half a knot is an additional five miles or about 3/4 hours per day less. My whole trip down and back in 13-14 only used just under 400 gallons (including full time generator while not at the dock) and my total cost including motoring and sailing in Florida was around $2,000 for 503 gallons. I averaged about $4.00 a gallon then. Today would be about $1,200 so fuel is not a significant cost, more about having enough range to avoid a lot of jerry cans and enough speed in the Gulf crossing to minimize weather impacts.

My prop had changed to a lesser pitch through erosion of the parts and when I took it off could only get 3100 RPM at WOT and so was very unhappy with the result and speed being very much lower. I had Ben cruising for years at 2750 at 6.2 knots. With my prop problem , I was at 2590 and 5.5 knots. That is a significant increase in time for the same distance. Since I cruise very loaded on a long trip, we are currently thinking the 20 degrees is maybe a better compromise. Up until I started having problems I was pleased with both fuel economy and speed. This weekend I hope to go out and compare speeds at 100 RPM increments and see where it shakes out.

It only took a couple of hours to put the whole thing back together and I should grease it every year anyway, so if I want I can keep it in the travel lift long enough to reset the pitch next year.




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[J Clark H356]

Originally Posted by groundtackle

I just cleaned up my two blade max prop. It works great and I love the prop walk. I try to avoid situations where I need to make the stern go to port in reverse but I can turn in circles in the other direction while making essentially no headway at all which proves very useful.
My max is an older one with no built in zinc that I think newer ones incorporate. It relies solely on the shaft zinc for protection. It's badly pitted and I think I'm going to have to replace it in a few years. Or someone mentioned restoring it? Can new metal be added to the pitted eroded areas effectively returning it to great condition? At what cost? Any recommendations for who is good at this process? The gears and inner workings appear in great shape (I've had it apart a couple of times)
Or alternately should I just think about replacing it in the coming years ($3500ish....ouch) and getting the benefit of the incorporated zincs.

Thanks
Nick


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Look on PYI's website and call Jerome. He gave me a range for mine of $400 to $1200 plus shipping before I sent mine out there. It cost $731.50 for repairs and new parts plus the return shipping. They can add metal to,the old parts. They were first class to deal with and I highly recommend working with them.


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[groundtackle]

Originally Posted by J Clark H356

Look on PYI's website and call Jerome. He gave me a range for mine of $400 to $1200 plus shipping before I sent mine out there. It cost $731.50 for repairs and new parts plus the return shipping. They can add metal to,the old parts. They were first class to deal with and I highly recommend working with them.


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Thanks I'll do that although I won't pursue it until my next haulout as I'm back in the water now
Nick


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[fstbttms]

Originally Posted by groundtackle

Thanks I'll do that although I won't pursue it until my next haulout as I'm back in the water now

So? You don't have divers in BC?

[jtsailjt]

Originally Posted by fstbttms

So? You don't have divers in BC?

While it's theoretically possible to remove and replace a maxprop under water, just one fumble fingered moment and you'll watch a critical part sink into the deep. This can be helped by rigging a sheet of fine netting below the prop to catch any falling parts, but I still wouldn't bet against having fewer parts when you finish than when you begin. Also, on the old fashioned ones where you adjust the pitch by carefully lining up the gears in a certain way, I think it would be pretty hard to see those small markings through a dive mask and through a foot or so of water. Since he'll have to haul out within a year anyway, and there's no big problem with leaving it as until that haulout, I think he's wise to wait and do it on the hard where it's easy and you're a lot less likely to lose any parts.

[fstbttms]

Originally Posted by jtsailjt

While it's theoretically possible to remove and replace a maxprop under water, just one fumble fingered moment and you'll watch a critical part sink into the deep. This can be helped by rigging a sheet of fine netting below the prop to catch any falling parts, but I still wouldn't bet against having fewer parts when you finish than when you begin. Also, on the old fashioned ones where you adjust the pitch by carefully lining up the gears in a certain way, I think it would be pretty hard to see those small markings through a dive mask and through a foot or so of water. Since he'll have to haul out within a year anyway, and there's no big problem with leaving it as until that haulout, I think he's wise to wait and do it on the hard where it's easy and you're a lot less likely to lose any parts.

I have personally installed, removed, repitched, lubricated etc., etc, etc, many dozens of Max Props of every model and type. 100% success rate, zero lost parts and many thousands of dollars saved (versus hauling out) for the boat owners. Don't attribute your fears due to lack of experience in doing this work to a professional diver.

But hey, it's his dime.

[jtsailjt]

Originally Posted by groundtackle

Thanks I'll do that although I won't pursue it until my next haulout as I'm back in the water now
Nick


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I think it's very worthwhile to have PYI recondition it. They'll return it to you with any pitting gone and all the gears in original condition even if it means adding metal. I had mine done a few years ago and when it came back it looked like new and worked like new. As long as they say your prop is still in good enough shape to be "reconditionable" I can't imagine replacing it instead. Not cheap but it's a lot less than a new one and they do a really nice job and are very straightforward to work with.

[jtsailjt]

Originally Posted by fstbttms

I have personally installed, removed, repitched, lubricated etc., etc, etc, many dozens of Max Props of every model and type. 100% success rate, zero lost parts and many thousands of dollars saved (versus hauling out) for the boat owners. But hey, it's his dime.

After your previous post, I pretty well knew this one was coming. You may well have the vast experience and high success rate you claim, I don't doubt it, but what percent of the divers he might end up hiring have that same level of experience with max props and installing them underwater? I doubt if he wants someone learning on his $3500 propeller. I've repitched and installed a couple of maxprops on land, and I dive recreationally and know a couple of commercial divers in my area that would be available if I needed to hire a diver in our local area. They seem very competent but I wouldn't let them take my maxprop apart underwater and I certainly wouldn't try it myself. With your extensive resume dealing with maxpprops, I might consider hiring you to do the job if you worked in my area, but I wouldn't hire just "a diver."

[fstbttms]

Originally Posted by jtsailjt

what percent of the divers he might end up hiring have that same level of experience with max props and installing them underwater?

PYI will happily recommend a qualified diver.