shaft size

[anaisdog]

i can't get to my boat for a few days - where the transmission shafts a standard size of 1 inch?  i'm 1986 hull 99 and i looked in the manual and can't find a diameter for it.  i want to get an magnesium anode for it, before i launch.

thanks

becki kain

[KWKloeber]

Prop shaft = 1"

[Ron Hill]

becki :    ........ and if it original it's bronze.

A thought

[anaisdog]

its not. the original, which was bent, is in my dock box

thanks!

[KWKloeber]

Ha!  Ballast?  A persuader?  Dock box theft deterrent?  Nunchuck?   

-k

[anaisdog]

well, i am in detroit....


do i need to use specifically "Tef-Gel electrical isolation compound" or is there a home depot replacement?  I'm not certain I can get it in time, to launch, to get it.

[Dave Spencer]

Becki,
If the Tef Gel is related to fitting your zinc, I've never applied anything to my zincs or shaft before i put them on.  I simply clean up the shaft with a scotchbrite pad or emery cloth where the zinc will be mounted to ensure a good electrical contact. I use magnesium "zincs" in the fresh water of Georgian Bay. If you've already bought a zinc "zinc", it will be fine for the year.  Magnesium is better is fresh water, zinc is better in salt. 
Good luck with your launch!

[KWKloeber]

do i need to use specifically "Tef-Gel electrical isolation compound" or is there a home depot replacement?  I'm not certain I can get it in time, to launch, to get it.

An anode MUST have great (not "good") electrical contact to be most effective.  We're talking millivolts difference in electrical potential between different metals that causes galvanic corrosion.

So, JTSO IIWMB, IW (others' mileage may vary)

1) Clean both surfaces well, w/ a wire brush on a drill for the concave of the anode (to bright metal), wet sand the spot on the shaft w/ say 800 grit.
2) Use SuperLube gel between them (more available than T-Gel).***  Or, possibly copper-based never seize between them, but SuperLube is a USCG mandated carry-aboard lubricant/protectant (found in any good hardware store) so everyone has that in their repertoire anyway.

Understand that, if the shaft isn't electrically connected to anything else the anode doesn't protect against galvanic corrosion due to dockside and boat electrical leakage (i.e., it must have electrical continuity to your 12v negative buss.)   It also doesn't protect the strut (due to the rubber cutlass bearing.)   So if you want to protect it, add an anode there -- there's recent posts (in last year) about doing that.

The shaft anode should be *close to* the strut, about 6", not in the middle of the span.


*** Just to clarify you aren't trying to "electrically isolate" the metals as T-Gel implies, you are preventing future corrosion between them.  The two surfaces cut thru the thin film of gel laid down and make electrical contact, and leave any open space with gel to protect the surfaces.


-k

[Noah]

Ken-Perhaps I am not reading you clearly, but I personally, wouldn't put SurperLube, Tifgel or anything between the zinc collar and the shaft itself, preferring unimpeded metal-to-metal contact. I can see where you could/would put it on the bolts/nuts that attached the collar and hold it tight to the shaft (and in the case of a prop, the bolts that attach anode to the end of the prop) but not to the mating surfaces between the metal that is to be protected and the sacrificial anode. Attached is a MaineSail discussion on this subject.

https://forums.sailboatowners.com/index.php?threads/anode-installation-best-practices.175835/

[KWKloeber]

Question Noah

What's the difference in this application vs using T-gel on an electrical installation?  e.g., a terminal on a post?  What's your reasoning to use it there but not here?

-k

Added:  check out the Tef-Gel product instructions and uses on the website, might be surprised.
Note that SuperLube is also the same, ptfe suspension, but I can't attest to the precise vehicle used in each product, just the HUGE cost difference.

[Noah]

I have never advocated "using it on a terminal nor a post", so I am not going to debate that one. I believe it is pretty standard best practices to leave the anode contact to protecting metal mating surface, free of any coatings. I do use Tifgel to isolate fasteners into dissimilar metals, such as stainless steel bolts into an aluminum spar.

[KWKloeber]

Then read the usage instructions on Tef-Gel, they speak to exactly this situation of "mating surfaces".
Many have advocated using it on electrical connections and it's absolutely proper.

[Noah]

Interesting that Mainesail, when describing "best practice " for fitting a shaft or prop zinc, mentions using Tef gel on the bolts/fasterners, but doesn't say use it on the mating surfaces, such as on the shaft or prop themselves...

[KWKloeber]

I agree.  So did you see the instructions?  tef-gel.com

I use the common sense test, step back and look at what is going on. 

1. The electrical connection is what's important.
2. The connection made thru the two faces is still an electrical connection like as made with a terminal on a post or on a terminal strip.   J and others have no issue using TG on an electrical connection. The fact is, the Teflon gets squeezed out of the "connection" but protects everything adjacent and fills any microvoids that occur and prevents future corrosion.  Same thing with the anode connection.

3. RC is slathering the bolts, and the TG remains there because there's space between the bolt thread and hole -- it isn't a pressure fit.  You could use anything.  Petroleum jelly, fill with epoxy and drill it out, bubble gum, whatever -- just so long as it isolates the two surfaces. 
4. with the contact surfaces, that's different -- you want the TG to squish out and leave fresh metal-to-metal contact.

5. 6 or 7 square inches of contact area on the shaft is unnecessary to make the electrical connection.  Not when the electrical connection to the negative buss is the area of a ring terminal.   My point being, even if there is a micro area (or even HALF of) where the faces meet that doesn't make contact due to TG, there's STILL WAY MORE than necessary.  And the remaining TG will fill microvoids and be a barrier to prevent weeping of corrosion into the interior faces of the shaft/anode and prevent deterioration of the electrical contact.  Same as it does on a circuit terminal strip or buss.

-k

[J_Sail]

Yes, you should get more than enough contact between a zinc and the shaft, even with Tef-Gel applied.

However, for some electrical connectors there is legitimate concern that the action of sliding the connector together, repeated enough times, can cause a microscopic smearing of the PTFE over a large enough area to cause a microscopic, but significant separation of the contacts, resulting in increased resistance.  That caused one manufacturer to reformulate their electrical contact lube to remove the PTFE particles.  I don't think that concern applies to most of your on-board uses.

I have a friend (we worked together as electronics engineers for years) in the contact lube business, so I tend to read the scientific papers from time to time. In most cases, for electrical contacts, a thin film of a very light viscosity anti-corrosion liquid is best, rather than a grease. The thin film protects fine and has less of a tendency to trap moisture or contaminants. That said, I have not seen any research on what works best below the water line, and hi-pressure/clamped connections are a different animal, anyway.  I suspect that Tef-Gel or most any marine-rated grease or anti-seize should be fine. 

Note that SuperLube makes a special anti-corrosion gel that does not use PTFE particles.  I don't know how well it protects underwater though. In turbulent conditions it might not stay in place around the attachment bolts as well. Anyone want to test it?

https://www.homedepot.com/p/Super-Lube-3-oz-Tube-Anti-Corrosion-Gel-82003/202932733