Fresh water to Salt water (Marine Growth)

[PierreR]

I have a question that I could not answer with an internet search. Will going from fresh water to salt water for a few days kill the bottom growth enough for the ablative paint to do its job?
My boat is currently in fresh water. Two months ago during survey, the bottom was power washed. The paint was in good condition but the bottom wash job left much to be desired. Two months later there is quite a bit of growth returned and by spring when I am ready to take the boat north, the growth will likely be at an unacceptable level.
I am hoping the change in salt will do the job but need to schedule a cleaning if it will not.

 

[rslifkin]

Moving between fresh and salt will usually kill most growth, but it may not actually fall off the boat. It'll just stop growing and may get easier to remove.

 

[PierreR]

I can find a lot of information of going from salt water to fresh in killing growth but virtually no information on going from fresh to salt on killing growth.

 

[READY]

You should plan to clean it. It is highly unlikely to just fall off. I would do it prior to your trip to improve speed and reduce fuel consumption.

 

[Marco Flamingo]

We kept a boat just inside the Ballard Locks (fresh water) for years. Almost once a week we would go through the locks and spend at least two days in saltwater. Painted the bottom when we first got the boat and it was still perfect 6 years later.

If we spent several weeks out in the salt, we might get tiny barnacles on some areas (like the external heat exchanger). Those would die and even dissolve and disappear over time because of the time spent in fresh water. The boat could do over 8 knots when pushed, and that seemed to be enough to clean even the scum.

Going through the locks for every outing might seem like a burden, but we were just inside and lived within a mile, so we went though at 6 in the morning and 6, or later, at night. No traffic and we had the maneuvers down. It certainly wasn't a waste of time like hauling out, prepping, and painting the bottom every couple of years.