Help! Need a new prop!

[dave_and_dd]

I have the boat (Catalina 309) out on the hard for bottom paint. there was a bit of 'chipping' on the prop (on the trailing edge). I thought it must've hit something in the water while in reverse.
They cleaned it up a bit and with just a (very minor) touch of sandpaper, a section about a 1 inch square just disintegrated out. There's even more just hanging like jigsaw pieces ready to fall out!

I don't have a pic of the prop after the pieces fell out. About 2 weeks ago, my diver said the zinc was OK, but if I didn't take the boat out for bottom paint, it should be replaced the next time he went down. When we hauled the boat (2 days ago), there was no zinc in sight...so unless he was wrong about it being there at all (which I don't think so), it somehow fell off after he last saw it.

Does this disintegration look like electrolysis? is there any way to repair...or no way other than a new prop?

Any ideas on best place to get a new prop quickly? Catalina doesn't have one, they can order one, but that will be weeks!

Any help will be most appreciated...Dave - Tampa, FL

 

[Ron20324]

Geeze. Are you plugged in at a marina?

 

[dave_and_dd]

Yes.... starting a couple months ago, I decided to keep the charger plugged in to keep the batteries 'tip-top'.

Dave

 

[SFS]

Dave, in the local area, try Don's Marine Salvage in Clearwater, General Propeller in Bradenton. Beyond that, do a google search for propellers in Florida. You'll need the diameter, pitch, shaft size, the number of blades you want, and whether it is right hand or left hand.

 

[LeoLambert310]

Too me this disintegration look like electrolysis as I had the same thing when I went 6 months with no zinc but not as bad. If the pitting area have a pink color to it that will indicate electrolysis. Before you spend any money on a new prop I would check to make sure that any electrolysis issue have been dealt with or it will happen again.

 

[The Garbone]

Get a solar panel and decent controller. I have a 50watt that I just sits on the housetop and we stow below when sailing. Our batteries are always at 13.4 ish when I get to the boat and no shore power for the last 2 years.

It may not be your boat. It could be a neighbors bad wiring finding a path thru your shore power cable.

 

[JamesG161]

Does this disintegration look like electrolysis?

Yes. Pitting is normally caused by rapid electrolysis. To all who read my post here...
Take the pictures of strut, shaft and prop from many angles BEFORE anyone touches them.

The outside edges of a prop start off new, thin, so expect the edges to thin, ding, erode, corrode etc.

Divers see what they CAN see. With cheap underwater cameras, my Diver will video my entire boat bottom, before and after his work, with close ups of thru hulls, keel, zincs and prop edges.

A zinc will appear OK, but loose and not electrically connected. The diver should try to move the zinc by hand, always.

My mechanic found a new prop and shaft (being repaired after purchase), in Tampa, for my boat within the 5 days of bottom paint, etc.

Lastly...
Just like what happened to my boat's previous owner, that had a reliable diver change zincs, 6 week before my Sea Trials inspection, we found major pitting on shaft, prop, and strut. It was hauled out with just a small piece of the zinc, dangling.

There was an electrical stray current in their marina. Buy a drop zinc to protect your new prop until you can resolve the rapid corrosion.
Here is the corrosion order, first to last...
1) Zinc
2) Bronze Prop
3) Steel strut
4) Stainless Steel Prop.

In short, if you have a Stainless shaft with NO PITS, then your prop was your "zinc"
Jim...

PS: If your diver dives, he should always change ≈$20 zinc, even if it is going to be bottom cleaned in a few days. Tip: Weigh the old versus new and record the time installed.

 

[dave_and_dd]

Hey thanks folks for the info. been busy getting this all taken care of. the mechanic working on it found a prop at a reasonable rate and put it on. the shaft looked to be in very good shape with no pitting/issue. added a pic of the old one after a quick sand-blast. the pic is in pretty low light, in other words, in real life it looks even more pink than it does in the pic! obviously electrolysis. i'll be sure to confirm my diver's zinc findings always in the future.

FYI, regarding electricity, i'm checking with the others in the marina. also - all the through hulls on the boat are marelon, so there's no bonding with them.

can one check with a multi-meter between the shaft and the water looking for a potential to see if there's an electrical issue?

 

[JamesG161]

can one check with a multi-meter between the shaft and the water looking for a potential to see if there's an electrical issue?

Perhaps using a pencil zinc clipped to one side of your DVM and dangling it in the water (about same depth of your shaft zinc). It would have to be significant stray. Plus you may have to move the spot in the water of the pencil zinc, kind of like a direction finder, to different spots around your boat.

What you would trying to do is detect a "electrical disturbance" between your shaft zinc and the pencil zinc. Worth a try.
Jim...

PS: I keep my old prop like yours for as emergency spare on board, with a nut and pin.

 

[Cayennita]

Pick up a discarded zinc from a powerboat. Buy large gage green wire 10'? Terminate both end with ring terminals and bolt one end o the hole on the zinc and the other to anywhere that you have ground wire. I used the turnbuckle on one side of my split backstay. In the water in the marina. In a bag still connected when sailing. It only takes on boat with a reverse polarity problem to mess up everybody.