It is a never ending battle to keep the boat bottom clean. In fact, I think it’s impossible, but we try. You get three kinds of growth. The sea cabbage grows all over the bottom. Its is leafy it is easy to remove by running a wide blade putty knife along the hull. There is a slimy but that seems to prefer the sunny side of the hull along the water line. It only comes off with a fairly aggressive (black) 3M \ Scotchbrite pad. And lastly there are the barnacles. They grow very sparsely along the hull and cluster on anything which is metal and thus not bottom painted, as well as LOVE the overhanging stern section which is always bouncing in and out of the water. On the hull they pop off with the putty knife. On the waterline and metals bits you really have to hack at them to get them off which uses considerable oxygen\energy.
We had been able to keep up with the waterline and the bottom fairly well by snorkeling. The stern is always a bit of a mess though, and the brand new paint on the waterline stripe is now scratched up badly.
The metal bits (deeper in the water) are just too hard to do via snorkel. I can’t hold my breath long enough and without a weight belt, you spend most of your time trying to keep from floating against the boat. Today we borrowed a dive hookah and weight belt from another boat, and man was it awesome. I spent about a half hour in the water and was able to hack all of the barnacles off the prop, shaft and gudgeon. Maybe that 1.5kts of boat speed we were missing will come back!
We use Petite’s Barnacle ban on our metal bits (prop, shaft, gudgeon). It seems to ban nothing, but when I did scrape them clean the grey paint was still there where it didn’t get scrapped off, so I think its doing ok.
Our boat sits perfectly on its waterline in calm water at the dock. But there is RARELY calm water at anchor. This is why people raise their waterlines. Not because they’ve overloaded the boat, but because at anchor your boat is always bouncing around and at all times 4-6 inches of your waterline are bouncing in and out the water. Filter feeders like Barnacles LOVE this! When we redo the bottom paint this next year I am going to look into raising the water line and I’m going to paint the stern overhang completely in bottom paint.
Zincs at Shilshole Bay Marina were replaced every six months. We haven’t been in Marinas much at all since November and the zincs are about 1/2 gone at 9 months. We’ll have the divers replace them when they clean the boat while we’re gone.
After today’s experience I can really see the benefit of a dive hookah. You could even use it for snorkeling in general. Unfortunately, retail dive hookahs cost \$2000 to \$5000 depending on the make and model. Not something that is in my budget right now, but it is possible to build your own for less than \$500 and I think I’m going to start looking into that.