DO LEGS DISSOLVE IN SALT WATER ?

DAKA

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Does any one have problems with legs in salt water ?
I have an old Corniche with 290 DP (1988), she is currently semi-retired berthed in a fresh water canal, only venturing into salt water for the summer season/holidays. The ZINC anodes on both the legs and engine are seriously depleted each year.
If I keep the old girl in salt water year round will I need to change the anodes every 6 months or does the corrosion slow down as the sea temperature cools in the winter?
Aluminum props also suffer will stainless help or speed up the leg problem?
Shore power in or out ?

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DAKA

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I used to use Magnesium on my last boat but you could actually watch them erode in salt water, it was like putting a cube of sugar in a pint of beer( I have a sweet tooth)
I dont think they would last a month in salt water, any one tried it ?
 

robind

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A certain manufacturer had a problem with the waterways in their legs corroding through and destroying integrity, necessitating complete renewal. so anodes are very important as is a suitable check of the wiring system for leakage etc.
 

oldgit

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Re Anode loss.

If the anodes are NOT corroding then you have a problem.Reckon mine lose around 3/4 of ring anode on outdrive leg and about 1/2 of bar anode on shield in 12months.Boat in water 51 weeks of year on half tide mooring.
 

tamarind

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Re: Re Anode loss.

Zinc anodes are used in salt water. If they are down to 50% they need changing. In some places corrosion is worse than others. Alloy props corrode alot quicker than s/steel, but usually it is electrolisis that gets to them ie pitted holes in the blades. Being plugged in to shore power will speed up the operation only a little but lots of boats around you all plugged in to power will increase the problem. My boat is in salt water all year round and have to replace anodes every six months
 

BrendanS

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A little more information required. If the boat is mainly kept in fresh water, you should have magnesium anodes. Zinc anodes will just get a coating on them, rendering them next to useless, so they won't erode, but are doing nothing

If you make short forays to salt water, ignore. If you make longer forays to salt water, they need to be replaced with Zinc for the duration you are in salt water.

You might consider using aluminium anodes whilst in salt water, take specialist advice, but while in fresh water, def need magnesium rather than zinc, or you will end up with possible damage.

If you end up in salt water year round, then zinc or aluminium are way to go. Mercury outdrives now come with aluminium anodes for sea water use, so as I said, take specialist advice on whether zinc or aluminium better for you set up
 

kingfisher

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What you could do is attach some heavy duty anodes, a true block of zinc, to a copper wire, and ground the wire to the les. When you leave the boat, chuck the block in the water, and let that dissolve, in stead of the expensive, tailor made, leg anodes.
 

tico

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Yup!
Mine is kept in a marina where its fairly brackish but used in salt water. Problem here is that the zinc anodes become covered with an insulating layer of zinc oxide and their effectiveness is reduced, hence electrolysis of props.
Cure was to fit a couple of aluminium anodes which protect in the brackish water alongside the zincs which give additional protection in salt water. Result........ props dont get electrlysis.
 

DAKA

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Thanks everyone for your valued input.
I will check my electircs, add a few extra alumninium anodes, throw a zinc anchor overboard and unplug all your shore power ( ok maybe not unplug 240v).
Thanks again. /forums/images/graemlins/smile.gif
 
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