Aluminum and Salt...and outboards

[CDMA]

I recently pulled the heads off my 150 yamaha and after 10 years I was amazed to see the waterjackets. It got me thinking my yamaha is now 11 years old with 2000+ hours on it. Always in salt and left in the water. Now when dealing with I/O's everyone is always saying how if you are going to run in salt water you can't have aluminum heads, intakes and so forth. I don't get it. When is the last time you heard of outboards failing because the block corroded through or the water jackets were clogged with deposits? I sure can't remember ever hearing that. On top of this aluminum when in contact with salt water oxidixes like steel but the difference is the coating that the oxidation of aluminum creates stays and prevents further oxidation. This is unlike steel or cast iron where once oxidation occurs you begin to see the formation of "scale" that eventually falls off letting more and more metal rust away. I started to give this some thought and looked into the outboards a little more. It apprears to me that my yamaha has no special coating or treatment on it and the properties of the aluminum used are similar to the properties of aluminum used in say automotive cylinder heads.

So basically why do we shy away from aluminum? Are we just being ignorant and going with " everyone says aluminum is bad in salt" so we just go on past precedent or is there reasoning? What am I missing here? Does the heat of the engine and the movement of the water inside cause the oxidation of the aluminum to be removed allowing for more oxidation to occur? And if so how do outboards get away with this? Or maybe dissimilar metals cause this in I/O's where in OB's they are almost exclusively aluminum therefore eliminating this variable.

Chris

Thinking too much

[harbormaster]

IT DOESNN'T STAY SHINY.

[CDMA]

????

[Woodsy]

Chris,

Check out this website. It explains the issues in plain english. I think you will find it very informative. I know I did.

http://www.diveweb.com/uw/archives/arch/uw-su99.04.shtml

Woodsy The Racoon :D :D

[Forrest]

Besides galvanic corrosion from dissimilar metals in an electrolyte (water) like in the case of an iron/aluminum inboard engine, an outboard power-head completely drains all of its cooling water every time the engine is shut-off. On the other hand, an automotive type inboard engine retains all of its raw cooling-water running or not. Also you will find that the aluminum an outboard is constructed of is a different alloy than that of aluminum automotive heads and intake manifolds.

[CDMA]

I see. Exactly what I was looking for. So say if you built an ALL aluminum inboard and drained the block every time you would be in good shape???

Forrest, I have been looking through my books and I don't think the alloy's are much if at all different. I could be wrong...It happens...every day...multiple times.

Ok back to my newest idea....

Chris

[Rootsy]

not being much of an outboard guru i wonder how many non-painted parts are clear anodized??? i have all of my aluminum tooling clear anodized because we use a lot of isopropyl alcohol sprayed in mist form to assemble most of our products, this gets on all of the tooling as well as grommets, etc and the alcohol causes serious corrosion issues with untreated aluminum...

[MOP]

Hi having gone to alot of schools on this stuff I have a little more input. Out boards are all aluminum and S/S parts which work well together also if you noticed they are coated with an epoxy type paint in the jackets. When you get the normal type automotive grade ( Cheap Cheap) aluminum you have to work at slowing down the mix of Galvanic/ Corrosion problems. Years back a buddy and myself stuck an aluminum V8 turbo Buick in a small flat bottom. We had the block acid boiled after we washed it alot we poured epoxy through the block and heads and all over hell in the shop. He ran the heck out of it for 5-6 years, he ate 3-4 turbos they would corrode and freeeze. When he blew it up we pulled one head to check it out and looked inside the hole in the block and it lloked real good inside. In salt you really have two killers, both can be tamed to a point. Any of you salt guys ever look inside a cast iron part that had water running through it. You will see the normal scaling and if you lok closely you will see what kind of looks like little volcano round bumps with holes in the top. I asked an istructor years ago what the heck that was. He said it was electrolis, I thouht BS. Well thinking about I decided to try an experiment, I took a large copper Tee with 3 inch nipples put in in my Formulars intake befroe the pump I screwed a big pencil zinc in it and grounded it to the block. I had that boat 4 years sold it to a buddy who finally after 3 years changed the exhaust elbows. That is 7 years on an item that 5 years is a real stretch in salt. That proved to me that incerting a big zink in the intake track slows the electrolosis down alot. I talked a few of my customers into trying it and the few I kept in touch with had the same results. Another point about electrolosis, is that flowing water produces more damage that still water due to the fact that you are constantly supplying fresh electrolite. BOY ALMOST RAN OUT OF WIND ON THIS ONE! Words from the Ole Fart!