Fouling - Salt water V's Fresh

[Nautical]

Fouling - Salt water V\'s Fresh

Sorry to ask a stupid question, but here goes.

If you move from salt water to fresh and vise versa every month or so, will any fouling from either die off in the opposing water or do the organisms that cause the fouling survive in both.

We have the ability to move from one to the other as there are several pontoons on the river side of the harbour, however will there be problems with the anodes etc and also does it put us at a higer risk of osmosis or other GRP problems.

Last question, if we do not antifoul but leave the bottom nice and shiny which at moment is giving us 2.5 knts over the factory figures or probably better fuel consumption at cruising speed will that also leave us more exposed to osmosis etc. In other words is antifouling a factor in preventing osmosis or other grp related problems?

Many thanks for any help.

 

[BrendanS]

Re: Fouling - Salt water V\'s Fresh

If you keep the boat permanently in fresh water, you will have few problems. Just a wipe off once a year.

If you move the boat regularly, then probably few problems. Leave it in salt water for more than a few or more weeks , and you'll need antifouling and seawater anodes. That's a given.

Moving from fresh to salt and back will kill most organisms.Can explain in more detail, but most cannot live in both environments

Antifouling is highly unlikely to prevent osmosis. For that you'd need a barrier layer, of which there are many

 

[hlb]

Re: Fouling - Salt water V\'s Fresh

My esteemed friend Brendan is indeed corect. Shuffeling from sea water to fresh will keep the undersides clean. Or there abouts. Osmosis is about water ingresion into hull. Nothing to do with this. Only crap hull!!!

 

[Nautical]

Re: Fouling - Salt water V\'s Fresh

OK guys thanks very much,

I did see somewhere on another board someone saying that you needed different type anodes for salt and fresh but I think that was for a merc leg, ours are the latest duo props with D6's.

Thanks again

 

[Solitaire]

Re: Fouling - Salt water V\'s Fresh

There are different anodes for salt and freash water. It's got nothing to do with the make of drive you've got! It's the environment in which you keep the boat. If you are moving from salt to freash, check with others in your area as to what they use. Local knoledge is good.

I found your post a bit odd in terms of saying that you were in salt water in one part of your mooring area and freash in another behind the harbour wall. I don't follow your logic. Does the other side of the harbour wall have a lock gate that filters out salt water in some way???

 

[Roy]

Re: Fouling - Salt water V\'s Fresh

Anti foul the boat for freshwater too, otherwise the hull gets slimy, then stained then layered with a skin thats hard to shift. Osmosis can happen to any boat with or without a/f. Happned on my last boat after only two years of life!

Magnesium for fresh and zinc for salt. If you are in both salt and fresh, then plump for zinc. Zinc in fresh won't offer much protection, if any and mags in salt water will literally fizz away in weeks. Another point - marine growth from salt water mainly dies off in frsh, but the encrusting and dead beasties remain stuck to the boat until removed. Get it antifouled to ease the removal process.

 

[Nautical]

Re: Fouling - Salt water V\'s Fresh

Thanks for that,

I did'nt think it made any difference whether you needed anodes or not depending on the legs that you have, I just thought particlular ones were more prone to corrosion than others but I probably got the wrong end of the stick as usual.

The harbour we are in has a reasonable river running into it and some of the poontons are up by where the river comes in at the top of the harbour. There are lock gates 2 hrs either side of HW so for quite a while that area has constant fresh water running through it. I raised the question in my ignorance because I noticed the boats up that end seem to have very little growth on them yet accross the harbour and further down there appears to be more fouling.

Thanks again