From The Forums

Published in the September 2011 Issue September 2011 News

People join the forum at for a variety of reasons. Sometimes they just want to chit chat with people who share similar interests. Sometimes they have information to share, and sometimes they're looking for help with a tricky problem. Longtime member, infrequent poster VOLintoon approached the group with an issue about corrosion, and quickly got the help he needed. Let's see how it happened.

VOLintoonVOLintoon said: Pulled my 2006 `toon out for yearly motor maintenance-plugs, oil, filters and this time, the water pump impeller. The inside of the impeller casing had what looked like a calcium buildup. It was wearing away at the impeller. Cleaned and replaced okay, but the bottom had the same hard buildup and even after hand scrubbing in the lake and pressure washing at 3100 psi, it still left a rough surface below the waterline that felt like 80 grit sandpaper. Two questions: does this happen to everyone and is there something besides ablative bottom paint as a cure? I did leave a battery trickle charger on for a while (electrolysis?). There is a zinc on the motor that had corrosion also. I wire brushed it for a fresh surface, but it wasn't really eaten away. The logs don't have zincs, should they? Any suggestions are greatly appreciated.

BigKahunaBigKahuna suggested an article he'd read: Hey VOLintoon! Check out this article I've attached:
What I'm getting from this article is that the zinc protection you have on your outdrive is inadequate and you must add more zinc or additional sacrificial anodes to protect the metals on your outdrive and the underside of your pontoons. Hopefully this will solve your problem.

VOLintoonVOLintoon came back with what he'd learned: Thanks BigK, I checked out your reference. Looks like zincs are a minimum requirement. A marina maintenance guy told me there are zincs attached to the motor raising assembly on my boat. Could not find them, even checked the Yamaha service manual for the engine, but no joy. Besides the little fin under the cavitation plate on the engine (that I assumed corrected for torque steer) I don't think the Bennington has them. Can't afford to take it back out to add zincs, maybe a zinc on a wire would be adequate until next year? Also, I found this aluminum bottom paint site that looks promising:

BatmanBatman shared his experience: I replaced my anodes with magnesium last year, and that stopped the corrosion.

VOLintoon had further questions: Hey Batman, where did you get magnesium anodes and where on your boat did you put them?

To read this thread in its entirety, visit the forums at and search for the "Fresh Water Corrosion" thread.

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