I am experiencing rapid corrosion of my aluminum Edelbrock heads on my 509. In less than 100hrs i'm getting water in #8 cylinder again. this happened the first time after about 4yrs with Felpro gaskets. this time I was using Cometics & the problem seems to be considerably worse. I also added an anode to the thermostat housing after the last repair. I had the heads welded & machined before going back with the cometics. I'm flushing the engine after every use & the boat runs in brackish water only except for a trip to Destin once a year. the Mercathode system is hooked up but i'm not sure if it's working. any idea whats making this happen so rapidly? many people in the area run aluminum heads for many years without a problem. most of my boating is in lake Pontchartrain so it's not very salty.

Replied to your other thread. In short, the heads are toast. If your running open cooling with aluminum heads and they are not hard anodized and your in saltwater the life expectancy will be 1-3 years. Your probably looking at a complete rebuild plus new heads. Exact same thing happened to me. I ended up repowering with all stock cast iron heads. After my experience I was not going to risk another $15K by relying on a hard anodized coating.

Well, sea water is an electrolyte and aluminum is electro positive to everything on earth, a BAD Combination.

I agree with the above statements but I know many people who are not having a problem running in the same area. I'm wondering if I have a ground problem & are the ss Cometic gaskets making the problem worse.

Stainless Steel + Aluminum + Salt Water = Galvanic Corrosion. Google it...

Are you flushing out using muffs on the drive? Some use the hose hookup on the engines starboard side & that doesnt do as good as the muffs.

I think I have a combination of problems. no battery switch so the engine stays powered up all the time. the stainless steel gaskets touching the aluminum directly. I need to verify the ground straps on the outdrive are good. I need to add water bleeds at the rear of the intake. need to add anodes in the heads. A good friend of mine has 10yrs & counting on his set.