Autoprop ?

[fstbttms]

Originally Posted by Benronpro

...we have continued on with our aged max-prop but observation has shown plenty of wear in the hub and cones which is revealed as play in the blades( I guess to be expected after 20 plus years of service) however it has proved very reliable thus far. Now the time has come to replace the prop.

You understand that you can have the Max Prop refurbished, yes?

[Benronpro]

Yes fstbttms, am aware of ability of maxprop to reconditioning their props. I am considering this option although have heard of cost to refurbish around $2000 plus cost of freight from Australia or Asia. At the end of the day the base metal in the prop is still twenty plus years old, food for thought. Would absolutely go with maxprop again if the price were not so prohibitive.

[Har2015]

Originally Posted by fstbttms

Not on the Autoprop. The manufacturer provides 3 really sh*tty plastic machine screws (called "Anode Retaining Screws") to hold a pyramid-shaped anode to the end of the body of the prop. Worthless POS- see below:



There is an aftermarket adapter that will allow you to install a standard U.S.-style prop zinc. The fact that such a product even exisits is indicative of the crappy design of the Autoprop:



Autoprop Adaptor page

Here's a good view of the plastic screws that fstbttms was referring to.


Sent from my iPhone using Cruisers Sailing Forum

[dkall]

Actually, with those 3 crappy screws I now know how to use them. Overtighten and I've never had a problem since. They act as a spring compressing the zinc to the prop. And if you search, I think Boatzincs.com has the anode quite reasonable.

[Yachts66]

HarborDiving, the link you posted does not work, could you fix it please?

[fstbttms]

Originally Posted by Yachts66

HarborDiving, the link you posted does not work, could you fix it please?

Autoprop Anode Adapter | Islers Diving

[Dockhead]

Originally Posted by dkall

Actually, with those 3 crappy screws I now know how to use them. Overtighten and I've never had a problem since. They act as a spring compressing the zinc to the prop. And if you search, I think Boatzincs.com has the anode quite reasonable.

Yes. Actually it's not the screws which are crappy, but the anode, which does not have enough "meat" around the screw holes, which allows the anode to fall off prematurely. The screws are fine -- plastic so that they are electrically neutral and plenty strong enough.

The anode problem can be solved by putting dabs of antifoul around the screw holes.

You need to change the anodes pretty often because all that surface area of bronze creates quite a lot of galvanic action. A shaft anode does nothing, apparently. So I do it every four months together with the 4.5 kg hull anode, which is also about half wasted by that time.

Once you get used to it, it's not too bad. I guess that most problems are caused by people not expecting to need to change them that often.

There are aftermarket sources of the anodes which make the cost somewhat acceptable; not like buying them from Brunton.

[fstbttms]

Originally Posted by Dockhead

Yes. Actually it's not the screws which are crappy, but the anode, which does not have enough "meat" around the screw holes, which allows the anode to fall off prematurely. The screws are fine -- plastic so that they are electrically neutral and plenty strong enough.

I disagree with this sentiment. Have you ever broken one of those flimsy POS off in the hole? I have, more than once. Without exception, every single other prop in the world that requires screws to attach an anode uses stainless or monel screws. Why? Because they too are corrosion resistant but unlike the Autoprop screws, are very strong. Like most aspects of Autoprop, the anode attachment screws are a poorly-conceived design for their intended purpose.

[hellosailor]

They look like standard [read: readily available] plain nylon screws which doesn't make then crappy plastic. I'd be concerned that plain nylon might not like the constant side torque on a spinning prop assembly, but as long as they are beefy enough to take that, nylon might not be such a bad idea. After all, if it does break off, it can always be unscrewed from the hole by pushing a hot screwdriver or other tool into it and instantly creating a new head. Guaranteed no galvanic issues. No way to damage the threads. NOT such a bad idea.


But the choice of installation location probably also means that as the zinc starts to sacrifice, it will get looser on the screw heads, which would allow more motion against the screw heads, which in turn has got to lead to problems. It just seems like putting the screws into a "thin" area has got to make that happen faster. Then it is just a question of whether the soft nylon or the soft zinc is going to fail first, isn't it?

[delmarrey]

Originally Posted by Dockhead

Yes. Actually it's not the screws which are crappy, but the anode, which does not have enough "meat" around the screw holes, which allows the anode to fall off prematurely.

The anode problem can be solved by putting dabs of antifoul around the screw holes.

Out of context a bit here, but do you know for sure the paint works. Max Prop also has the same 3 screw configuration but with SS screws. I find myself replacing zincs long before they're used up due to the meat around the screws is gone before the center section is even half gone. I've been tempted to drill and tap a center hole just for extra wear. Once those holes are eaten away the zinc is no longer tight/bonded enough to do its job.

I'm tempted to design my own mold and pour my own zincs with more surface area around the holes. Or other wise mfg a center section (adaptor) similar to the Autoprop that will take a regular clamshell type for prop shafts.

[fstbttms]

Originally Posted by hellosailor

After all, if it does break off, it can always be unscrewed from the hole by pushing a hot screwdriver or other tool into it and instantly creating a new head.

Yeah, that's great. Unless the screw breaks underwater, which is where it is likely to happen if the boat stays in year 'round, which most boats do.

Originally Posted by hellosailor

Guaranteed no galvanic issues. No way to damage the threads. NOT such a bad idea.

As I mentioned before, every single other prop in the world that requires screws to attach an anode uses metal screws. And I can tell you from servicing many thousands of such props, galvanic issues are not a concern. So why did Brunton's feel it necessary to use nylon?

The bottom line with this is that the cons outweigh the pros.

[exMaggieDrum]

We put good quality electical tape around the circumference of the zinc base on our Maxiprop to help delay the erosion of the zinc at the mounting holes. I was very surprised that this would work. I thought the tape would not stay on (it did but clean the area well first). And I didn't think it would affect the metal as much as it did. It dramatically improved the useful life of the zincs.

I cleaned the zinc with acetone or alcohol first, used 3M 33Super electrical tape, and put it on tight and neat. Just two complete wraps.

[hellosailor]

fst-
You could still use a Yankee (push) drill to simply make a new hole in the nylon, and then bang in a slotted screwdriver, or a cut nail. (The Yankee version of a Robertson bit.(G) In any case, it still beats trying to chew a broken metal screw shaft out of there!

[Dockhead]

Originally Posted by delmarrey

Out of context a bit here, but do you know for sure the paint works. Max Prop also has the same 3 screw configuration but with SS screws. I find myself replacing zincs long before they're used up due to the meat around the screws is gone before the center section is even half gone. I've been tempted to drill and tap a center hole just for extra wear. Once those holes are eaten away the zinc is no longer tight/bonded enough to do its job.

I'm tempted to design my own mold and pour my own zincs with more surface area around the holes. Or other wise mfg a center section (adaptor) similar to the Autoprop that will take a regular clamshell type for prop shafts.

Yes, I've been using that technique for years. That way they last for the four months it takes for the rest of the anode to become fully wasted.

There might be better ways to do it -- with adapters etc. -- but I finally decided not to bother with it, since this method with the normal anodes works ok.

[Dockhead]

Originally Posted by fstbttms

I disagree with this sentiment. Have you ever broken one of those flimsy POS off in the hole? I have, more than once. Without exception, every single other prop in the world that requires screws to attach an anode uses stainless or monel screws. Why? Because they too are corrosion resistant but unlike the Autoprop screws, are very strong. Like most aspects of Autoprop, the anode attachment screws are a poorly-conceived design for their intended purpose.

No, I've never broken one off, in almost 20 years of using Autoprops. They are very tough. Monel or stainless would react with the anode and shorten its life, unlike the plastic. I don't have any complaint about the screws. What I think is stupid is the lack of metal around the screw holes. I've had anodes fall off (in my first year or two of Autoprop life), but never had a screw fail. The screws are left behind, mockingly, when the anode falls off

But this is cured with a bit of antifoul or prop wax.