Damage fron charging batteries incorrect and not Saltwater

I just bought a used 1984 Ranger 373V and it had a 1984 Mercury 150 on it that looked as though salt water had eaten away at the lower unit. It has white pock marks eaten into the lower unit. The mechanic that is checking out everything on the boat and motor for me says this is actually from something the previous owner did wrong when he charged his batteries.
Has anyone ever heard of such a thing?

I'm nervous now because I just purchased a 3 Bank Minn Kota on-board charger and I want to be sure I have no issues. I only paid $1200 for the boat, motor,trailer, and custom cover so I think I made out pretty well.

Thnx

Foodeefish

Re: Damage fron charging batteries incorrect and not Saltwater

He charged the batteries with the boat in the lake, and there was current flowing between the ground wire on the battery charger and the water, through the motor. No safety grounding and an internal fault in his battery charger. Through some strange stroke of luck, or maybe divine intervention, nobody got fried.

hope it helps
John

Re: Damage fron charging batteries incorrect and not Saltwater

i got that before. mechanic told me it was from the boat dock not having somthing grounded out properly. electrolisis. my anodes were all ate up too.

Re: Damage fron charging batteries incorrect and not Saltwater

flatcat77 said:

i got that before. mechanic told me it was from the boat dock not having somthing grounded out properly. electrolisis. my anodes were all ate up too.

Click to expand...

Depending on how bad the fault was, faithful anode maintainance might have saved the LU. If in fresh water, anode erosion is a sign of electrolisis caused by a ground fault.

hope it helps
John

Re: Damage fron charging batteries incorrect and not Saltwater

I am also aware of the "grounding" issue with a motor left in the water and regular battery charging maintenance is performed. The motor anodes should take care of this problem but alas are only as good as the maintenance they receive, i.e. periodic removal of the crusty deposit formation on their surfaces. This Merc is like mine and has two anodes. The main one is the one that is attached below the power trim lift ram and bolts to both sides of the transom bracket. The other is actually the trim tab itself. Normally, the main one will coat out with deposit and must be wire brushed down to the base metal again (zinc is the metal for the anodes and should be bright silver when clean). Also, when the main anode has coated out with corrosion, the trim tab itself will begin to corrode out more. When I perform maintenance on mine, I pay particular attention to the underside of the anode mounts for any corrosion. The anode success is only as good as the contact it can make with what you are protecting.

Some friends on Toledo Bend have had this electrolysis phenomenon also occur and came up with a couple of things that seem to minimize this problem severity. The first is the obvious one, take the boat out of the water on some frequency and perform maintenance on the motor anodes. The second is to install a safety main electric switch called a Perko switch to completely isolate the motor from any battery charging.

Hope this helps.

Jim

Re: Damage fron charging batteries incorrect and not Saltwater

A simple modern technique would be to use a GFI circuit to power the chargers. A small amount of current escaping to the water would trip the breaker.

just my 02
John

Re: Damage fron charging batteries incorrect and not Saltwater

Thanks everyone and the GFI sounds like a great idea.