To wash or not wash

[Styge]

To highlight my lack of experience keeping a boat wet I will now ask the dumb question.  Should I pressure wash the pond scum (kept in a very northern harbor for three months) and risk taking the bottom paint off with it, or just ignore it until its time to add another layer of BottomKote?

Let the comments fly!!

[NateD]

Personally, I would power wash it. If it is flaking off in places, the power washer will blow those chunks off, so plan on touching up any of those areas with new paint. But if it is well adhered, and you keep the pressure washer wand a foot away from the hull it probably won't remove the paint, just the scum.

[brackish]

I generally do a gentle growth removal wash in water at the end of each season using a sponge mop.  After three season I pull the boat take it to the self car wash and pressure wash it with vigor.  Then, when  I get the boat home I pressure wash it again with my equipment.  Then put several coats of my preferred multi season bottom paint after light sanding, then another three year cycle.

In my experience, a gentle rub with a sponge mop will remove all the growth and slime while minimally removing the ablative bottom paint but if you are going to pressure wash you should be ready to repaint.

When I was in salt, my process was different.  Pressure wash will not remove barnacles. 

[Styge]

I'm leaning toward a "not too close" pressure wash at this point.  I'm thankful I didn't pick up any barnacles.  My outboard wasn't so lucky.  Since just the tip was still making contact with the water in the raised position and tilted even, it turned into a little science experiment!

[MacGyver]

Wash it off, otherwise as it dries it puts the surface under a different tension than that of which the paint was designed for, and will start peeling layers off anyway, which most times is worse damage than that which is washed off.
Kind of a science behind it all summed up.

Mac

[crazycarl]

if you have a gravel surface to wash it on , use that.  i found washing it on the asphalt drive, the little bit of paint that comes off runs into the lawn and kills it.

[philb Junkie19]

Pulled the boat and dinghy yesterday. The 19's bottom was still wet when I got it home. Gave it a scrub with a stiff brush with a hosing set to jet. This was enough to get the slime and immature barnacles but a pressure wash would have been a whole lot easier.  I'm wondering that the ablative bottom paint prevented the barnacles from maturing as the dinghy at the dock with no bottom paint only had the hard mature ones, and plenty of them. (The dinghy also had been pulled and scraped of hard barnacles and weed in august)

On the dinghy the barnacles came off with a good plastic scrapper. My problem there is with the some other critters. They are very flat and round ranging from dime to larger than half dollar size with a soft outer body and very hard inner attached surface. Scraped, they leave hard circles or rings and a very rough surface. The only solution that comes to mind is light orbital sanding followed by a coat of epoxy before bottom paint. Thoughts on this?m

The unpainted dinghy was new to me this year and I skipped bottom paint as I could't figure the waterline. Clearly no difficulty there now.

[Styge]

Crazycarl, no need for me to worry about killing the lawn.  Most people in SE Alaska don't bother with lawns.  Or asphalt!  Gardening for me consists of taking a chainsaw to the Alders every couple of years. They grow like weeds!

[Styge]

Just read about a practical sailor article that mentions using Desitin rash ointment as a cheap alternative to bottom paint at $16 a tub!  It's apparently 40% zinc oxide.  So I guess I'm gonna try butt paste on my bottom unit!  yeah, that didn't come out right!