Painting on aluminum question

Okay I've done alot of reading on how to prep/repaint an aluminum boat but there seems to be alot of different answers. Here's my situation. I plan on using steelflex on the bottom exterior hull and up to the waterline. I want to repaint above the water line exterior and possibly the inside (although I may just go w/ Durabak for the inside). There is already an old paint job on this boat that is fading. Should I sand and strip to get down to bare aluminum and then apply a self etching primer or should I sand and then just paint over it. I'm confused. Do you need primer if you are painting over an old paint job?

if the paint is just good, I would go over it with sand paper and while you don't have to primer over it again - it will make the paint last longer so you wouldn't have to repaint for a few more years. You can also get by not using self-etching primer although I recommend it. I used a zinc chromate primer over an existing factory paint and that paint job turned out great

thanks for the quick reply Russ. How much time do I have to put the new coat of paint on after I apply the primer?

I've done both with great results. But if taking down to the bare aluminum I would use the self etching primer. I just did a deck on my boat and used a self etching primer over existing paint and so far so good. As far as how much time you have I'd say that you have a day or two to paint over the primer with out having to sand it. After that I'd say that you'd have best results by lightly sanding the primer.

I painted my boat the day after I put the primer on... I did it outside in the Georgia heat in August... if you look for my old boat, I posted the entire process there.... forget it - I'll do a search and post the link back here

Here's the link... painting starts on page 2

https://tinboats.net/forum/viewtopic.php?f=13&t=4493

Here's the process I would recommend - it worked for me and the paint still looks good on that boat a year later (I don't have it anymore, but see it every tournament we have since a guy in my club bought it).

1 - sand it down with a wire wheel from walmart (goes in your regular drill - get 2.. like $5 each)
2 - let it dry and wetsand it with 300 grit sandpaper at night (if you paint during the day).. if you paint at night, you'll probably have to wait til next morning
3 - put a light coat of paint on - multiple light coats will last much longer than 1 big one... and the finish will be better too. Let the first coat of paint dry completely (maybe 5-6 hours depending on your location and the temperature).. wetsand it again and then put a light 2nd coat on (little thicker than the 1st). When it's tacky and not shiny-sticky, put on the 3rd coat a little lighter than the 2nd coat. When the 3rd coat is completely dry (maybe 24-48 hours because that 2nd coat has got to dry too), you can lightly wetsand it again to take out any blemishes if there are any with the paint (runs, drops, etc.)

Now if you're brushing it on, it's a completely different story, but still the same process. Either way you do it I suggest getting a medium reducer (available at parts stores that sell auto paint). Mix it at a paint to reducer ratio of 5 paint to 1 reducer (get a mixing cup at the parts store too, it will come in handy). The reducer will make your paint go a lot farther, and if you have some paint left over after the 3rd coat, put another coat on the bottom - you'll be glad you did!