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Old 12 October 2007, 14:46   #1
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Unexplained Corrosion

I have a 7 meter Rib tech with twin Mercury 60ph’s. Set up works like a dream after experimenting with the trim by using Bags of sand from Tesco’s, top tip I picked up on here!!

Any way I diverge. I seem to have some unusual corrosion to the sacrificial anodes by the props as norm. But one has corroded considerable but not the other.

I have heard a couple of interesting theories on this topic some more plausible than others. Can anyone help??
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Old 12 October 2007, 15:10   #2
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Is the boat kept in the water ?
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Old 12 October 2007, 17:26   #3
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Originally Posted by Timmmy View Post
Any way I diverge. I seem to have some unusual corrosion to the sacrificial anodes by the props as norm. But one has corroded considerable but not the other.

I have heard a couple of interesting theories on this topic some more plausible than others. Can anyone help??
Don't know if I can help or not, but there are a few things that could be checked:

Check the resistance from both engine blocks back to the battery negative terminal. You may find that one is not quite connected as well as the other.

Check all bonding wires, and make sure theyre tight (you may want to disconnect them and give them a good cleaning.)

Last, take the anode that is not disappearing, and make sure it has a clean connection to the base metal it's protecting.

jky
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Old 13 October 2007, 09:10   #4
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Rectifiers may be the cause

I have a 50hp EFI 2002 myself which suffered very bad corrosion; The motor was handed in for service after cooling failure alarm. The powerhead was taken off and there was severe corrosion on the plate separating the rig from the powerhead as well as corrosion to the rig itself. Altogether repairs should have cost about GBP 3000. Fortunately the importer picked up the bill for the parts(GBP 2000). I think it was caused by the weakness this engine has with the rectifier(there is a manufacturer recall on this). I had two batteries completely emptied and of course this electricity needs to go somewhere and it will create damage getting there. I think the electricity went through the powerhead and into the copper tube leading the cooling water to the powerhead and then to ground(seawater).
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