Difference betwen FWC and RWC?

[Darkhorse1201]

Stupid question and not sure where to post but what is the difference between a fresh water colled engine and a raw water cooled engine? I though there were only 2 kinds - open and closed systems (closed using antifreeze like a car). I thoght a knew a bunch about boats but this one has me asking. Thanks

 

[DukesFin]

Re: Difference betwen FWC and RWC?

Still 2 kinds... Closed is FWC and Open is RWC.

 

[trog100]

Re: Difference betwen FWC and RWC?

its a bad name really causing the confusion.. calling it a closed cooling system makes a lot more sense..<br /><br />trog

 

[Dunaruna]

Re: Difference betwen FWC and RWC?

Raw water cooled - the lake/river/ocean water cools the motor.<br /><br />Half fresh water cooled - a heatexchanger full of coolant cools the motor. Raw water cools the manifold(s).<br /><br />Closed fresh water cooled - the manifold(s) are cooled by the coolant also.

 

[trog100]

Re: Difference betwen FWC and RWC?

its playing with words.. whatever system is used its ultimatley cooled by the lake/river/ocean.. its just done either directly (raw water) which to add to the confuson in lakes/rivers could be fresh water.. or indirectly via a heat exchanger and some other medium less corrosive than salt water on the engine side of the heat exchanger.. which at one time really would have simply been fresh water.. salt water is the bad guy.. fresh water never has been..<br /><br />coolant can and is water or a water anti-freeze mix.. its just the medium that ultimately either directly or indirectly transfers the heat from the engine to the lake/river/ocean..<br /><br />the term fresh water cooled shows how far back this terminology goes.. anti-freeze was something u but in your cast iron car engine during the winter months to stop it freezing.. during the summer u drained it out cos "fresh" water was considered a better coolant than a water/antifreeze mix..<br /><br />fresh water cooled really did mean fresh water cooled when the term was originaly coined.. boats that were laid up during the summer would have had no need for anti-freeze at all.. salt water boats would have simply got flushed with fresh water then drained.. the anti corrosion properties of antifreeze wasnt was even a thought..<br /><br />its only over the past twenty years and the common use of aluminium cylinder heads and blocks (mostly in cars) that it has been considered neccessary or even beneficial to run an antifreeze/water mix all year round mostly cos of the need to protect the aluminium engine parts from the affects of corrosion..<br /><br />so the term "fresh water cooled" might have once made sense cos it would have been the stuff actually on the engine side of the heat exchanger.. but it dosnt any more.. fresh water dosnt enter in the modern day equation in the slightest.. now it should be "coolant" cooled.. which of course makes no sense at all.. he he he<br /><br />if i have a "coolant" leak on my car i still call it a "water" leak.. cos water was the "coolant" used most of the time back in ancient times.. i imagine that younger dudes would or should actually say "coolant" leak.. dunno.. as for fresh water.. i dont spose anybody would dream of putting it in their engine cooling systems.. but it aint that long ago that folks did..<br /><br />trog

 

[vampirefish]

Re: Difference betwen FWC and RWC?

So how do I know if this boat I'm going to check out tonight is FWC or RWC? The engine is a Mercruiser V8 305cu in (in a 95' bayliner capri). Thanks!

 

[Doug Durako]

Re: Difference betwen FWC and RWC?

Closed cooling has a heat exchanger (big metal tube just a bit bigger than a one-liter pop bottle). Run it on the muffs at 1,200 rpm until the engine heats up and opens thermostat (might take 5 to 10 minutes)---then make sure the fresh water coming into the heat exchanger from the muffs cools it to 180 degrees (or less), and keeps it there.