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Old 30-01-2015, 11:31   #16
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Re: Salt vs Fresh water ?

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Originally Posted by gbgreen59 View Post
There are a lot of fresh water boats with rigging up and no cover during winters, where there is ice and snow...freezing and thawing all winter. I would stay away from these, or seriously look for damage from freezing and thawing.
How is that different from a salt water boat with rigging up and no covers during winter?
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Old 30-01-2015, 11:36   #17
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Re: Salt vs Fresh water ?

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1. Take that one with a BIG grain of salt. Boat engines, like rigging, come from the boat builder as they were built, not where they were intended to be sailed.
Exactly and the point I seem to have such difficulty making. These companies make boats. They don't know or care if you will be running them in salt water or fresh water (or both as I mentioned above). And they don't know what the next owner will be doing with the boat. They do not make boats specific to salt or fresh water.

As for the difference between raw water cooling and closed cooling, again, the manufacturer does not know what will happen to the boat once it's out the door. Boats built to a lower price often have raw water cooling. There may be an option for closed cooling at an additional cost. Boats built to a higher standard or with more expensive engines will usually come standard with a closed cooling system.
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Old 30-01-2015, 12:38   #18
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Re: Salt vs Fresh water ?

Normally, I thought fresh water boats were valued higher than the exact same boat used in salt water.
First boat I surveyed had some small almost like spider cracking in the deck in one place, moisture meter said it was wet there, boat had come from the great lakes and we assumed moisture had gotten in and the freeze thaw cycle cracked the deck.

That I think is only temperature related and has nothing to do with fresh or salt water.
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Old 30-01-2015, 13:17   #19
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Re: Salt vs Fresh water ?

I just happened to google ; what the difference between 304 ss & 316 ss for making antenna mount poles today. It so happens that 304ss will pit ( rust ) easier than the 316 ss because of the chemicals in the making of each . I'm pretty sure there is a strength difference in there somewhere also .
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Old 30-01-2015, 13:45   #20
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Re: Salt vs Fresh water ?

Spider-like cracking happens even on salt water boats. The cracking frequently occurs near cleats or other fixtures where stress is involved. While further damage from cracking may occur from water entering the deck at the cracks that's typically not the origin. Lots of old boats have cracking and if the boat is covered in the winter further damage is limited.

There are folks who have literally removed the entire deck surface on the old Tritons and rebuilt same. The builders used balsa wood for cores and laid the blocks of wood with the grain running parallel to the deck. The balsa wood rotted and softness occurred. Really not worth the time and effort but the Triton crowd is a loyal (read: NUTS!) group. I love 'em.
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Old 30-01-2015, 15:26   #21
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Re: Salt vs Fresh water ?

Consider what the salt on the roads during the winter does to the concrete on bridges and walkways, aggravating freeze damages. Much the same effect on grp plus I believe the salt accellerates the hydrolysis of the polyester by water, slowly resulting in osmosis damages. Even if you wash the hull thoroughly at layup, some salt stays in microscopic fractures preventing the hull from drying out completely even during the winter.


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Old 30-01-2015, 15:46   #22
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Re: Salt vs Fresh water ?

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Consider what the salt on the roads during the winter does to the concrete on bridges and walkways, aggravating freeze damages. Much the same effect on grp plus I believe the salt accellerates the hydrolysis of the polyester by water, slowly resulting in osmosis damages. Even if you wash the hull thoroughly at layup, some salt stays in microscopic fractures preventing the hull from drying out completely even during the winter.


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There is no single, or composite, material from which you can construct a boat that ISN'T affected by salt, rot, heat, ice, sunlight, waves, loading, unloading, or age.

I think you shouldn't waste any money on a boat. They sound like just so much trouble.
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Old 30-01-2015, 16:30   #23
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Re: Salt vs Fresh water ?

Note that a raw-water cooled engine, even if it's only used in fresh water, usually has a thermostat set for a lower temperature. This is undesirable to some degree because impurities aren't cooked out of the lube oil as well. Probably only a minor concern though.
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Old 30-01-2015, 21:44   #24
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Re: Salt vs Fresh water ?

What comes to engines raw water cooling was far more common in the past. In boats used in fresh water they keep ticking but in sea engine blocks have detoriatet ages ago.. That why they are more common in fresh water.
Locally in some areas smaller vessels (like row boats) are made with fastening only for fresh water use in mind. This is true especially with traditional models..
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Old 30-01-2015, 23:36   #25
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Re: Salt vs Fresh water ?

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I've also heard stories of fresh water boats suffering higher incidences of osmosis due to the differance in size/density of the water molecules.
You are quite correct; what you heard are stories.
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Old 31-01-2015, 04:53   #26
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Re: Salt vs Fresh water ?

My point was only that I doubt salt water to be less corrosive to grp than fresh water.

The only feature on the boat itself that could possibly benefit from salt water is a bare teak deck, provided that you dunk it regularly with sea water and let it dry. That you gladly accept the increased tear and wear in exchange for more interesting destinations is a completely different story - right?





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Old 31-01-2015, 08:31   #27
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Re: Salt vs Fresh water ?

I've been a marine engineer for a large part of my life and have a little bit of knowledge about cooling systems on engines.

1. If you an a conventional engine with a cast iron body, don't worry about saltwater corrosion. You most likely won't see any effects in your lifetime, as with any engine do regular maintenance on any filters and pumps
2. If you have one of the newer light weight engine blocks, it most probably has a closed freshwater/coolant cooling system and you shouldn't worry either. Any corrosion now takes place in your heat exchanger which can easily be taken out and cleaned (chemically)

By the way saltwater corrosion in your cooling system means a scale will form inside your engines cooling channels. No leaking holes will suddenly appear, it will only affect the heat transfer through the walls. Personally if an engine had been in fresh water for a long time, I would be more worried about marine growth (the zebra things) blocking the cooling channels than corrosion scaling. We had that on a 39' CS located in Lake Huron.

Robert
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Old 31-01-2015, 16:49   #28
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Re: Salt vs Fresh water ?

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Originally Posted by FilBrown View Post
I've also heard stories of fresh water boats suffering higher incidences of osmosis due to the differance in size/density of the water molecules.
WTF? A water molecule is the same size no matter what other ions are associated with it. Your statement makes no sense whatsoever.

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Old 31-01-2015, 18:49   #29
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Re: Salt vs Fresh water ?

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Originally Posted by robertandmj View Post
I've been a marine engineer for a large part of my life and have a little bit of knowledge about cooling systems on engines.

1. If you an a conventional engine with a cast iron body, don't worry about saltwater corrosion. You most likely won't see any effects in your lifetime, as with any engine do regular maintenance on any filters and pumps
2. If you have one of the newer light weight engine blocks, it most probably has a closed freshwater/coolant cooling system and you shouldn't worry either. Any corrosion now takes place in your heat exchanger which can easily be taken out and cleaned (chemically)

By the way saltwater corrosion in your cooling system means a scale will form inside your engines cooling channels. No leaking holes will suddenly appear, it will only affect the heat transfer through the walls. Personally if an engine had been in fresh water for a long time, I would be more worried about marine growth (the zebra things) blocking the cooling channels than corrosion scaling. We had that on a 39' CS located in Lake Huron.

Robert
Perhaps the engine block will not corrode but the risers and manifolds of a raw water cooled engine in a salt water environment will often fail in as little as five years, usually causing catastrophic damage to the engine. Preventive maintenance calls for replacing these parts at five year intervals or less.
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Old 31-01-2015, 19:03   #30
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Re: Salt vs Fresh water ?

I sailed on a 30-year old Ranger 29 with a raw-water cooled Atomic 4, in salt water. The owner eventually had to repower because the cooling water passages completely rotted out.
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