aluminum/brass fuel tank corrosion

[Seahunt]

Help I am looking for some ideas. I have my aluminum boat in saltwater usually 10 times a month on the average the last 4 years since new. About a month ago my fuel guage started reading 3/4 when full, then I saw a hole in the removeable aluminum floor plate over the tank and through this 1/4" hole I could see brass lightly touching it. I opened the floor plate, it had a peice of soft foam covering the brass fuel elbow. This super compressed foam wore through and the two were touching and created some corrosion which gummed up the fuel sender that was only 2" away.
I am planning to make a clay mold of the space between the floor plate and this brass elbow so I can know how much space I have to put a insulating spacer. Any ideas?
I also thought I might put slicone grease on the brass elbow and put 5200 over the top and in the hole in the floor plate. This would seal insulate and fill the hole in the floor plate. It just doesn't look as professional but only a small 3/4 plug would do it. What do dogs think?

[Metal Manipulator]

Your are right about the brass fitting Causing a problem. As you can see brass and aluminum do not do well together, combine them with salt water and you have created a battery. Electrolisis, corrosion is the results. I would find a way to remove the brass from the area mainly because moisture can still make the connection unless you can incapsulate the brass completly and permanently.

[Seahunt]

PM sent. I should have posted here. I believe replacing the brass is the best, these brass elbows on fuel aluminum fuel tanks always eventually cause problems. I am looking for ideas for reliable materials

[Pilar]

SS will work but you still have the dissimilar metals battery problem. The induced voltage is much lower and the corrosion rate much slower. Better than brass but still not perfect.

If you could find aluminum fittings that would be the permanent fix.

Brass has copper in it and that is what eats the aluminum.

[Seahunt]

Thanks for all the advise guys. I have decided to go with stainless elbow. My boat builder says aluminum for a fuel elbow scares him, if it became a victim of corrosion. Stainless with an annual check and dielectric silicone grease is going to be the fix till I hear something better. This brass elbow has been a problem for me on other boats with aluminum tanks. I guess it is a cheap way out for builders.

[smalldog]

Check the green grounding wire that goes to the tank also.
Make sure there is not more than one ohm resistance between the tank and battery ground.