If you are looking for a fiberglass lobster boat, you have come to the right place. About the only aluminum fabrication going on here is probably towers, masts, fuel tanks and so on, but maybe there is someone here who can help you. It's a pretty diverse group.
I can tell you that if aluminum has been around salt water, depending on the grade, it can be difficult to weld. I have a acid that cleans well into the pores of the alloy and makes it work better than just grinding. It can be found at any welding supply.
If you are interested in AL work boats you have to look to the Northwest US and Can BC, not the East. There are many places in northwest where AL is king and many builders. All types of AL work boats small and large are everywhere on this side of the rocky Mts Why AL? Its light-It's tough-It's low maint.-It's easy to clean with a power washer-It's easy to mount stuff on fasteners or weld-If you know what you are doing its easy to build a strong high performance durable boat unfortunately not as good looking as a DE.