Corrosion on 2007 Sea Ray

[Seattle Steve]

Hello all,

We made an offer on a 2007 Sea Ray 290 and have a few questions for this incredibly helpful community.

History: The boat has been stored in a freshwater slip, but has gone in and out of the salt water. The owner replaced BOTH outdrives in 2013 due to bad corrosion.

When we pulled it out of the water for inspection, it was surprising to see a fair amount of corrosion on the NEW outdrives. I don't seem to be able to attach images here for some reason, but the mechanic recommended that we replace some damaged parts (hydraulic block) and repaint, estimated at $1000.

The mechanic suspected that the marina may be "hot" and leading to the aggressive corrosion problems, but I wonder if there could be a problem with the boat itself in terms of how it's wired, for example, stray current that's leading to the issues?

I also wonder if the boat shouldn't have magnesium instead of zinc since it's 99% of the time in fresh water instead of salt?

I also found this article: http://www.boatus.com/seaworthy/magazine/2011/april/corrosion.asp

Any comments or advice would be appreciated, thanks!

Steve

 

[Lazy Daze]

There could be stray current from a nearby boat or the marina... there could be a neighbor that has poor anode protection and causing your anodes to pull double duty... there could be an issue with your Mercathode system... Hard to tell from here, you know? :smt001

All anodes pretty much look the same. It should not have 'zinc' on there - but just because they're grey doesn't mean they're zinc. Aluminum is always the safest choice as it works great in both types of water. Sometimes, Magnesium can over protect (even in fresh water) and cause problems. BUT - find a local (experienced) boater that has a similar setup as you and copy.

 

[paulswagelock]

I am docked in fresh water. When new, boat was shipped with aluminum anodes. I saw some mild corrosion by the end of the first year.
I switched to magnesium, and never saw any additional corrosion.
I agree with the above poster, ask local boaters at your marina what they are using, then look at their outdrives.

 

[CougarCruiser]

try to post up some pics (click Go Advanced) -- and you can add/upload photos then.

Surface corrosion should be expected if the boat got new drives 12-18 months ago. anything beyond surface level would be unusual. Bravo 3's can be a bit finicky as well because of the giant anode at the end of a stainless prop. Different metals can react differently sometimes. (not everyone will agree with me on that, I can just speak from my observations).

If it really is just the surface corrosion... I would have necessary parts replaced that sustained unusual wear from the corrosion, and ask the seller to discount the price enough to cover re-painting the drives. You should have the zinc's swapped for at least aluminum - but I'd say that's your cost as that is a future investment. You might squeeze in some extra dollars to have a mechanic go through and check all of your electrical grounding/bonding system. Does that boat have a galvonic isolator? If not, consider investment in one.

Lake Union is a little 'hot' just because of the number of boats in such a small area, the variety of boats that have a high risk of emitting stray currents, etc...

If the drives are really12-18 months, then I would expect you have ALOT of life left in them. If it were the original drives, you might faint with how much corrosion you would see had they not been exceedingly well maintained.

Not everyone who boats is crazy and maniacal about maintenance like us forum folks can be.

 

[BillK2632]

Definitely need magnesium anodes in freshwater and you have to stay on top of them. Make sure the Mercathode system is working. Inspect the bearing carrier, once corrosion starts there, in my opinion it is more than cosmetic. Without seeing pictures it's hard to know how much "a fair amount of corrosion is". I really like the way the BIII performs, but just hate the maintenance required to keep a BIII boat in the water. My 290 had them, it ran great, but Mercruiser also replaced both of them due to corrosion - they were the old style (2000) and the replacements were the new style with additional anodes (2003) once I had the upgraded drives with magnesium anodes, the corrosion was held to a minimum, but never totally eliminated.

 

[BillK2632]

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[Lazy Daze]

Guys, PLEASE don't recommend to someone that fresh water MUST EQUAL magnesium anodes. You cannot make this a "blanket" statement. As I mentioned above, sometimes Mg can CAUSE corrosion in fresh water. It all depends on the water. The best way is to check with locals. And the local you check with should be someone who has been in those waters for at least a few years and has had a good track record (no corrosion).

 

[BillK2632]

Dennis - Good point, magnesium anodes are not a blanket item for all freshwater applications.

In my case the issue was:

1. Wrong anodes
2. The Mercathode system was not working properly.

Mercruiser sent someone out to test the hull potential and check for stray current etc. at my slip. The recommended switching to magnesium anodes and they replaced the mercathode system and both outdrives. This pretty much stopped the corrosion issues.

 

[CougarCruiser]

I know lots of boaters in Steve's area (myself being one of them). most folks end up with Aluminum anodes if they stray from zinc because they do use their boats in the saltwater. I think that's a good switch to consider.

And i think the appropriate resolution would be to repaint the drives, replace any parts that are particularly corroded, and have the mercathode/electrical/bonding system checked out. Seems pretty manageable.

Steve -- was the estimate you received to repaint both, or per motor? if it was for both, then the corrosion must be very light. I think when I got some estimates on a Volvo DPS drive a few years back, it was about 2000 per side to pull them,blast them, repair them, and repaint them.

Where did you haul out? Gallery Marine or CSR?