Corroded prop and grounding sytem 3270-gctid371251

[Bodie]

When I pulled my 3270 last summer to adress an overheating problem, the port prop showed signs of corrosion (stbd was fine). The first thing I noticed was no anodes on the prop shafts so I added them to both. Afterwards, I was told by several people (here at BOC and by a fellow at the boat yard) that 3270's didn't normally have anodes on the shafts and that the boat's grounding system took care of protection from corrosion. I thought to myself that the football anodes I had added would take care of the situation, irregardless of what was going on with the grounding system. Not so, I've just pulled the boat again to replace the damaged prop and see that it is corroded even worse than it was when I looked at it last time the boat was out of the water. The stbd prop is still undamaged.I had a good look at the bonding wiring in the engine bay yesterday and see that from the main bonding wires running along the centre of the floor, forward to the engines, there are short lengths of wire T'd off near each of the dripless shaft bearings. One short wire has the remains of a ring or spade type connector at its end, and is long enough to have once been connected to the shaft bearing (or something else in that vicinity) in some way. The other short wire is devoid of any signs of a connector, but is also long enough to reach the area of the shaft or shaft bearing. There's no apparent way to attach wires to the shaft bearing itself, but there are signs, on both shafts just forward of the shaft bearings, that there may have been something, like a brush, touching the shafts at one time - there are light scratch marks, ringing the shafts, about an inch and a half forward of the shaft bearings.I vaguely recollect the PO saying something about the dripless shaft bearings being fairly new. Is it possible he just replaced the old bearings, which had some form of attachment for the grounding wires, with the new bearings and didn't bother re-attaching the ground wires? Replacing those bearings seems like a job for a professional, and it doesn't seem likely a professional would leave the grounding sytem incomplete.Four questions then:1. Is there supposed to be some way to attach the ground sytem to the shafts, or to the bearings?2. If both ground wires have been unattached, why did only the port prop suffer such extensive damage while the stbd prop remains unblemished?3. Why did the anodes I placed on the shafts not prevent further damage to the port prop? They have been doing some kind of sacrificial work, because they are pitted.4. Can badly pitted bronze props be repaired?I'm going to the boat in a while and will take some pictures of the dripless shaft bearings and wires and post them later today. Below are a couple of pics of the damaged prop:

[img]/media/kunena/attachments/vb/674656=26458-Prop1.jpg[/img]

[img]/media/kunena/attachments/vb/674656=26459-Prop2.jpg[/img]Here are a couple of pics of the shaft seals:

[img]/media/kunena/attachments/vb/674656=26517-shaftseal1.jpg[/img]

[img]/media/kunena/attachments/vb/674656=26518-shaftseal2.jpg[/img]

[boatworkfl]

What you need is a shaft brush on both props, you also need zincs on the shaft, I always use 2 zincs on each shaft, one near the strut, just close enough so if a shaft comes loose the prop will not hit the rudder, the other about 18" to 2' depending on the clearance, I always use the heavy duty zincs and use the ones with 4 screws, do not forget to use a hammer on the zinc to seat it, do this 2 times as you tighten.

That prop is dead, what size is it and LH or RH?

http://www.fisheriessupply.com/product/Pro-Mariner-20035-SHAFT-BRUSH-GROUNDING-DEVICE.aspx?cid=7590

[Bodie]

"That prop is dead, what size is it and LH or RH?"

It's 17X18 RH.

[boatworkfl]

Bodie wrote:
"That prop is dead, what size is it and LH or RH?"

It's 17X18 RH.

Search Ebay, there are a lot of props turning up, sometimes you can find a great deal, what is the shaft size?

Search Nibral propeller, bronze, and brass, sometimes inboard propeller.

[Guest]

I pay attention to any information I can find about galvanic corrosion, or what ever you want to call it. Partly because it relates to my trade, but more so because I own a boat. I've found that over the years, that there seems to be as many different opinions as there are publications. Most of which seem to have merit in some way or another.

I have come to the conclusion, that with fiberglass boats in particular, a common electrode and a secure bonding system is a good thing. The key here is "secure". If there are any poor connections in the system, it can create more problems than it can solve. Your bonding system is just one more system on your boat that has to be maintained to the highest level.

If you have a common bonding system, then shaft brushes are also a good way to go, but they do require a minimum amount of maintenence. If you use the boat a lot it's probably not an issue because they will "self clean" and keep the contact surface free of corrosion. If the boat sits for long periods then the contact resistance between the brush and shaft can become less than acceptable, introducing another problem.

It has been said before, but boats, like women, require constant attention, but with the right amount of attention they are certainly worth the effort.

[boatworkfl]

One of the best articles I have found.

http://www.google.com/url?sa=t&rct=j&q=yachtsurvey.com+bonding&source=web&cd=2&ved=0CDUQFjAB&url=http%3A%2F%2Fwww.yachtsurvey.com%2Fcorrosion.htm&ei=YZ6LT6WRB4Gg8QTe2qS8CQ&usg=AFQjCNFWFGTise5e6kR7oN3ICG4ihUZJ6A

http://www.yachtsurvey.com/corrosion_in_marinas.htm

[Bodie]

boatworkfl wrote:
Search Ebay, there are a lot of props turning up, sometimes you can find a great deal, what is the shaft size?

Search Nibral propeller, bronze, and brass, sometimes inboard propeller.

Thanks for the info, but I've already replaced both props with the spare set that came with the boat. Now I'm trying to find out all I can about the ground bonding system, to stop this from happening again.

The props that I replaced were 17x18, the spares that are now on the boat are 17x17. How will that affect the boat's performance? My thinking is that the lower pitch will drive the boat at (whatever) speed with slightly higher rpms than it took to drive it at the same speed with the other props. Am I right?

[boatworkfl]

Bodie wrote:
Thanks for the info, but I've already replaced both props with the spare set that came with the boat. Now I'm trying to find out all I can about the ground bonding system, to stop this from happening again.

The props that I replaced were 17x18, the spares that are now on the boat are 17x17. How will that affect the boat's performance? My thinking is that the lower pitch will drive the boat at (whatever) speed with slightly higher rpms than it took to drive it at the same speed with the other props. Am I right?

About 100 to 200 RPM higher.

[smitty477]

Bodie,

This is not normal. Are you at a marina and plugged in to shore power? Do your boating neighbors have similar problems? Do you have any 120vlt sources attached to the engines? Do you have block heaters? Do you have aftermarket battery chargers wired against the engine ground?

Please check carefully to see if any line voltages and/or grounds are wired near or to the engines or batteries.

Hope this helps

[boatworkfl]

smitty477 wrote:
Bodie,

This is not normal. Are you at a marina and plugged in to shore power? Do your boating neighbors have similar problems? Do you have any 120vlt sources attached to the engines? Do you have block heaters? Do you have aftermarket battery chargers wired against the engine ground?

Please check carefully to see if any line voltages and/or grounds are wired near or to the engines or batteries.

Hope this helps

ADD: Did you have an aluminum boat next to you?

[Bodie]

Deleted double post

[Bodie]

smitty477 wrote:
Bodie,

This is not normal. Are you at a marina and plugged in to shore power? Do your boating neighbors have similar problems? Do you have any 120vlt sources attached to the engines? Do you have block heaters? Do you have aftermarket battery chargers wired against the engine ground?

Please check carefully to see if any line voltages and/or grounds are wired near or to the engines or batteries.

Hope this helps

The boat is in the water, plugged into shore power. I replaced the failed battery charger last spring and wired it exactly the same as the old one had been wired. What do you mean by "wired against the engine ground"?

No aluminum boats nearby, and I haven't heard of any others having similar problems. No block heaters. Normally the only things running are the battery charger and a small heater.

One thing that has concerned me is the fact that until a couple of months ago the boat was in a small marina with a pretty sketchy "power grid". Lots of extension cords running all over the place to some sketchy looking boats, some of them liveaboards. Now I'm in a high end marina with a very professional power system. Maybe that's where the problem began...

[Guest]

Are those black wires in the photos not supposed to be tied in via brushes to your shafts? Were they originally?

[boatworkfl]

Bodie wrote:
The boat is in the water, plugged into shore power. I replaced the failed battery charger last spring and wired it exactly the same as the old one had been wired. What do you mean by "wired against the engine ground"?

No aluminum boats nearby, and I haven't heard of any others having similar problems. No block heaters. Normally the only things running are the battery charger and a small heater.

One thing that has concerned me is the fact that until a couple of months ago the boat was in a small marina with a pretty sketchy "power grid". Lots of extension cords running all over the place to some sketchy looking boats, some of them liveaboards. Now I'm in a high end marina with a very professional power system. Maybe that's where the problem began...

The only way to check your bonding system after checking all the connections is to use a "silver/silver cloride half cell" you do not need the meater normally sold with it, just a good multimeter able to show mili amps, FLUKE meters online has instructions for this. This is the only proper way to check the corrosion status on a boat. We have even used this system on buried pipelines.

I keep one cell on my boat in Alaska and just bought one for here in Florida.

[boatworkfl]

Shallow Boy wrote:
Are those black wires in the photos not supposed to be tied in via brushes to your shafts? Were they originally?

Good catch!

I missed that one, the marks on the shaft look like that is what they were for, I cannot see where the brushes were mounted.

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