cleaning and bottom painting my aluminum Starcraft Islander

[rolmops]

This summer I slipped my boat in  Sandy creek near Lake Ontario. This boat has always been on a trailer and I did not really consider growth and scum. Before too long I will have to pull the boat and I am painfully aware that my nice white boat bottom is no longer white. 

I have to clean the stuff off the hull to get it nice and white again and then I will have to put some type of bottom paint on it so I will not have the same problem next year.

Now this hull is aluminum, but it is covered with the original factory paint. So what material should I use to clean it up with and what type of paint can I use as a bottom paint?

Thank you.

Edited August 27, 2025 by rolmops

[MCF]

It has been a number of years since I have had a boat in the water so I am sure someone will respond with the latest to clean it.   As for bottom paint, I had a 22 Sylvan aluminum and there is special paint with a different base ingredient in it.    I think it was a name brand called Micron but can't recall.    There is a base coat to apply first.   I got it at West Marine at the time.

[Salty Nut]

Slimy Grimey is the best cleaner i have ever seen. The warm water mix per the instructions does matter too.

I got this from a friend a few years ago, its a little pricey but its worth it!

[SamonSez]

How does it compare to Mary Kate?

[Salty Nut]

Dont know anything about that product.

I had a fiberglass hull that had crude on it for a couple years, not just a water line but crude.

Mixed this up sprayed on with garden pump spayer and 10 minutes, gone. 

Had a few spots that needed a second hit but i was shocked at how it worked

[Slimer]

I keep a 19ft aluminum polarkraft in a slip from end of April to middle of October. The first year was a disaster. I let the buildup dry when I pulled the boat out and cleaned it a few weeks later. Since then, I pull it out once in the middle of the summer for mid year oil change and give it a scrape while it’s wet. At the end of the slip season I use this star brite hull cleaner https://a.co/d/3LwgpsN. My boat is unpainted below the waterline. 
 

I dilute it, spray it on, and let it sit for a couple of minutes. When it’s done foaming I take my push broom and scrape. For tougher spots I use a painters multi tool. 

[Bad Habit]

Is the Slimy Grimey good for the buildup on and outdrive too? I've tried many things over the years but haven't found anything that works very well. I usually use On-Off but it still leaves a lot of buildup.

[Salty Nut]

Slimy Grimy got that too

I think i brushed that with a scrub brush though too

[AnglingAddict]

Absolute first thing to do as soon as it's pulled and the growth is still wet is to power wash as much of it off as possible - it will make the rest of the job exponentially easier....