Bottom Paint on Aluminum Boats

[jrogers]

What do you guys think about bottom paint on aluminum boats? My Keani River boat sits in the fresh water all summer long, and I just pressure wash it off a few times, and use some acid cleaner on occasion (I forget what the chemical is, but it is clear and diluted with water). My new boat will be 31' and I will have a slip. I expect that it will be in the water for 5 weeks at a time, and will live on a bunk trailer otherwise. Is bottom paint worth the time/hassle/money?

Remenber the salt water here in Alaska ranges from maybe 34-50 degrees F, so I assume the buildup will be slower than what you Florida guys see.

Jim

[Chaps]

You might be fine if 5 weeks is it. However, though you might not get much growth the bottom will get kind of raunchy looking with a significant stain at the waterline. If you don't like that then painting is always an option later.

There is an earlier post somewhere about painting alloy boats that might provide more help.

[peterbo3]

Avoid the bottom paint. I have left a previous alloy boat in the water for a month & pressure washed it clean afterwards. And the water temp around here is similar to FL.
That is the beauty of alloy. You can use a really powerful water blaster with no ill effects.

[Ironwood Boats]

Hi

Two things to consider are the local temperature of the water and how much the boat is used.

Most of the boats we build that go up north do not get bottom painted.

For 5 weeks I would not be worried but if any signs of barnacles show up then power wash it and/or paint it. Power washing the base of the barnacles is a slow process with a 4000psi unit. Not getting all the barnacle off will affect the fuel economy. If you decide to paint the bases of the barnacle can be ground off when the aluminum is prepped for paint.

If are you concerned about fuel economy then use a roller to get the paint on. After the paint is on then go over it with a brush and keep the brush strokes parallel to the keel.

FYI.....For safety sake I rather say something than not......The packaging on many aluminum cleaners/brighters does not show it but they are strong (Hydrochloric/Hydrofluoric) acid solutions. It is one thing to get it on you skin and wash it off but if you get it in you eyes or under your finger nails.......

[CanCanCase]

Hi again Jim!

Since you're building a SeaWolf, ask Stennar what I've got on mine... I can't think of the name of it offhand (painted before I swiped the boat from Dad...)

We're going on the 7th year now, and other than spraying the drive units, I haven't touched anti-fouling paint. A few observations:
When I keep the Can Can in the boat house, the brown slime is non-existant, but I do get a tiny bit of green "moss" that comes off easily each time I run her up on step. One summer the curtain of the boathouse was left open for 2 weeks, and the green growth doubled in size/length quickly. When she's in the boathouse, the portion that never sees sunlight (bow) doesn't grow at all. The transom and stern end of the hull are where all the growth occurs because a bit of sun light (ahem) does get to it.
During charter season, if I'm out of the boathouse and parked outside daily, the brown slimy goo begins to grow fairly quickly... not bad enough to warrant a diver as in SanDiego, but it will certainly cost you 1 or 2 knots at cruise if allowed to grow.
For a boat that's used daily, I might not worry about paint, but if it's going to sit in the water for more than a few days at a time, I would paint it. Besides, that beautiful shiny metal turns a gorgeous dull grey that's complimented by a white bottom and a boot stripe color of your choice!

-Case