zinc wear

G

gettinthere

.
Nov 26, 2008
1,970
Endeavour 42 Cruisin
I have a cone shaped zinc on my maxprop and a few inches away I have a collar zinc on my prop shaft.
Twice now I'm seeing the maxprop zinc show significant loss while the shaft collar zinc shows very little during this time. Time frame is 2 to 3 months.

If I lost the maxprop zinc, would the shaft zinc cover everything?

Both zincs seem to be set well. I did the last change on land and made sure contact was good for both.

Is this just a case of one zinc going first? I expected both to go at about the same rate.

The zincs are from different sources. Perhaps a different compound eats away faster?
 
thinwater

thinwater

.
Mar 26, 2011
3,671
Corsair F-24 MK I Deale, MD
Yup, there is VERY high probability that the alloy is different. Perhaps one is aluminum. Find out and report back.
 
JamesG161

JamesG161

SBO Weather and Forecasting Forum Jim & John
Feb 14, 2014
7,745
Hunter 430 Waveland, MS
This is an educated guess....

As long as your zincs are electrically connected to propeller and shaft then one will serve you well.

If I understand right, the cone one, which I have seen screwed on the thread of the shaft and caps the prop, then...

These types are in the "prop wash" area. Cavitation or just plain silty water will "erode" (not react) that zinc. If it is "pitted", then cavitation of prop. If it is "streaked", then silt wear.

Normal sacrificial zinc anodes will "react" away evenly as it does its job.

As to "enough protection".....

Your call...

Most check/replace annually. If there is zinc and it is connected to shaft, you are protected. Weigh the new one and weigh the old one for a percent loss over time. That is the right way to know.

Fact....
Only when different metals are connected electrically in water to conduct electricity, will the metal weakest (Nobel series) have galvanic corrosion.

Zinc is weaker than most metals so it reacts instead of the other metals like brass, steel, stainless... etc.
Jim...

PS: other factors can cause zinc to react faster. Stray currents caused by badly wired boats or harbor wiring can react away zinc very fast. I have a 10 lb zinc that I hang over the side, when transient berthing to assure i don't lose the key one.
 
All U Get

All U Get

.
Oct 2, 2008
3,810
Pearson/ 530 Strafford, NH
Same with mine so I reasoned the shaft is stainless and only needs a few electrons. The Max Prop is brass and eats more of them. I bought a set of zincs from Max prop to see if theirs would last longer than the ones from Camp. The boat is on the hard yet so I won't know for quite a while. I always have plenty of zinc left on the prop, but the studs are usually worn through. Stupid design.

All U Get
 
G

gettinthere

.
Nov 26, 2008
1,970
Endeavour 42 Cruisin
Definitely zinc

Hmmmm, cavitation. Hadn't thought of that. The shaft donut wouldnt see the same kind of turbulence.

The prop, prop zinc, shaft and shaft zinc are all connected within less than a foot of each other.
 
D

Don Lucas

.
Jan 12, 2011
930
Hunter 410 full time cruiser
My last boat had a Max Prop and my current boat a FlexOFold prop. Both have cone zincs on them and on both boats the cone zinc on the shaft corrodes faster than the shaft zincs.
 
JamesG161

JamesG161

SBO Weather and Forecasting Forum Jim & John
Feb 14, 2014
7,745
Hunter 430 Waveland, MS
Not to drive home a point without seeing a snapshot of it....
But...

You only need ONE zinc to protect your shaft/prop combination.

If and only if the Brass prop is NOT insulated electrically from the shaft.

Use a volt/ohm meter in Resistance setting of Ohms. Touch one probe to prop and other probe to shaft. If you get near zero resistance on your meter then you are electrically connected.

Now....

The zinc must do the same. Touch one probe to zinc and one to prop and then shaft. If you see near zero resistance then Wahh Lahhh you are done.

ZiNC is for all connected metals. Not a zinc for the brass and a zinc for the shaft.

I hope i am helping.
Jim....
 
Charles Erwin

Charles Erwin

.
Jan 30, 2012
1,140
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
This propeller is a remarkable assembly of moving parts - and surprisingly reliable. Considering how Maxi propellers operate electrical connectivity between shaft and prop parts is unreliable.

So the rule with Maxi is one anode for the shaft and one anode for the propeller. Change both at the same time - no later than when the first is 50% wasted.

Charles
 
G

gettinthere

.
Nov 26, 2008
1,970
Endeavour 42 Cruisin
The zincs I bought for my maxprop were specified as zinc, not aluminum.

PYI does offer aluminum anodes as an alternative for fresh water boats, I've had that conversation with the guy in charge at PYI when I was in fresh water. The standard anode from PYI is zinc.

Interesting idea that the mechanism of the prop might cause some resistance. But the zinc is attached to the hub which is press fit to the shaft. I could see resistance existing out on the blades since they are floating in grease inside the hub.

Someone keeps referring to maxprops as brass...they are bronze.
 
fstbttms

fstbttms

.
Feb 26, 2011
1,440
Achilles SD-130 Alameda, CA
JamesG161 said:
You only need ONE zinc to protect your shaft/prop combination.

I hope i am helping.
Click to expand
I wish you were. Anode protection is a function of anode surface area to metal being protected. The more metal being protected, the more anode surface area required to protect it. You cannot generalize and say one size fits all. It does not.
 
fstbttms

fstbttms

.
Feb 26, 2011
1,440
Achilles SD-130 Alameda, CA
Charles Erwin said:
This propeller is a remarkable assembly of moving parts - and surprisingly reliable. Considering how Maxi propellers operate electrical connectivity between shaft and prop parts is unreliable.

So the rule with Maxi is one anode for the shaft and one anode for the propeller. Change both at the same time - no later than when the first is 50% wasted.

Charles
Click to expand
Please, it's "Max Prop." There is no "i" in the name.
 
fstbttms

fstbttms

.
Feb 26, 2011
1,440
Achilles SD-130 Alameda, CA
gettinthere said:
Interesting idea that the mechanism of the prop might cause some resistance. But the zinc is attached to the hub which is press fit to the shaft. I could see resistance existing out on the blades since they are floating in grease inside the hub.
Click to expand
The anode on a Max Prop is attached to the end cap, not the hub. The end cap is screwed onto the spinner halves, which are screwed around the hub. Only the hub has any reliable contact with the shaft and its anode(s).

gettinthere said:
Someone keeps referring to maxprops as brass...they are bronze.
Click to expand
Nickel aluminum bronze, to be exact.
 
JamesG161

JamesG161

SBO Weather and Forecasting Forum Jim & John
Feb 14, 2014
7,745
Hunter 430 Waveland, MS
I wish you were. Anode protection is a function of anode surface area to metal being protected. The more metal being protected, the more anode surface area required to protect it. You cannot generalize and say one size fits all. It does not.
Click to expand
Sorry but I didn't generalize. Please read my entire thread. One zinc WILL protect all connected metals. We used to ask a question to show a point about an "unknown".

"How many balls of string does it take to reach the moon?" Ans:
"ONE if it is long enough"

Understanding Galvanic corrosions is not too complicated. Some metals corrode a different rates so the combination of surface area exposed and renewed "like prop friction" will change the rates.
So...

Experience for your boat, water salinity, temperature, scouring, metal types and zinc (mass and surface area) all affect the protection.

Which is why i said in my earlier thread.

As to "enough protection".....

Your call...

Most check/replace annually. If there is zinc and it is connected to shaft, you are protected. Weigh the new one and weigh the old one for a percent loss over time. That is the right way to know.
Click to expand
Jim...
 
fstbttms

fstbttms

.
Feb 26, 2011
1,440
Achilles SD-130 Alameda, CA
JamesG161 said:
Most check/replace annually.
Click to expand
Maybe where you do your boating. I can assure that where boats stay in the water 24/7/365, an annual check is considered poor maintenance by knowlegable boaters and boat mainteneance professionals.

JamesG161 said:
If there is zinc and it is connected to shaft, you are protected.
Click to expand
Yes, but is the protection adequate? A single anode protecting a long run of prop shaft and a large prop? Likely not. Certainly not for a reasonable length of time.

BTW- galvanic corrosion is only one of several types of corrosion from which anodes protect our underwater metals. It is not a catch-all term for all the corrosion that pleasure craft are subject to.
 
R

Rick486

.
Oct 1, 2007
1,865
Boston Whaler Super Sport Pt. Judith
As a general item for your use. I buy my MaxProp zincs from Defender because they are much more zinc for your money than the PYI supplied zincs. The PYI MaxProp zincs are hollow where the Defender MaxProp zincs are solid zinc.
 
Maine Sail

Maine Sail

.
Feb 6, 1998
11,701
Canadian Sailcraft 36T Casco Bay, ME
It could partially be different metallurgic makes ups of the zincs but also remember your Max-Pro zinc probably weighs half of what your shaft zincs do... Equal errosion of a cone zinc often looks worse than it does on a streamline shaft zinc... Weigh them when new then weigh them when you replace them and my guess is you'll find went down fairly proportionally...
 
All U Get

All U Get

.
Oct 2, 2008
3,810
Pearson/ 530 Strafford, NH
Sorry about the brass remark. Would if be fair to say the zinc closest to the more noble metal protects it better than one further away? Would it also make sense that a zinc in quiet water erodes slower than one subject to currents? Lastly moving your boat from salt water to brackish or fresh water, like the AICW, would really confuse the little zinc?

All U Get
 
Gunni

Gunni

.
Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Try cleaning the back surface of your MaxProp with emery paper, then loosely attaching your shaft collar zinc and tap it snug to your MaxProp. That should give you a larger contact surface. If your MaxProp has not been off the boat for a number of years, it is possible that it has a poor contact with the shaft. I switched to aluminum anodes a few years ago and note that they dissolve more uniformly and completely. My zincs were salting up and staying more or less intact. Not good.
 
fstbttms

fstbttms

.
Feb 26, 2011
1,440
Achilles SD-130 Alameda, CA
Gunni said:
I switched to aluminum anodes a few years ago and note that they dissolve more uniformly and completely. My zincs were salting up and staying more or less intact. Not good.
Click to expand
It sounds like you were using zinc anodes in brackish or freshwater. They are not suited for this.

 
Gunni

Gunni

.
Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
I spend time in all salinities and suspect that any significant time in brackish causes the zinc to "salt", effectively stopping it from working. That is not an issue with aluminum anodes. Aluminum being much more reactive.
 
You must log in or register to reply here.

Top Bottom