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Old 07-22-2015, 12:39 AM   #21
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Hard to find a nice clean large yacht with dry stack. Why not- dirty upper decks. For fishing boats lots to like about dry stack with no worries about submerging exhaust with a big catch on board.

Either works, one way is really messy but many don't care about soot on the interior cabin sole.

For the last few months I have been intermingled with lots of commercial fishermen - lots of soot flying around.
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Old 07-22-2015, 06:14 AM   #22
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"Either works, one way is really messy but many don't care about soot on the interior cabin sole."

The working fish boats frequently have high time engines , idle for hours glazing the cylinders and run near full throttle at times.

No big deal if there exhaust is foul.

On a white boat the engines are usually kept up more frequently.and seldom idled for hours.

For a refit the use of double wall stove pipe with the engine exhaust pipe installed inside works well,,

Except its hard to install a dry locker for drying clothing.

The exhaust can be silenced with a "hospital critical" muffler , usually mounted on the cabin top.

IF a wet exhaust manifold is available , the keel cooling will handle the load .

If not, there are many exhaust wraps that work well, and the ER ventilation can be upgraded.

The final thought is a by pass thermostat is required in the KK cooling circuit.

The engine thermostat may keep the engine at 180F , but the return coolant at perhaps 80F - 100F is way to cool. It should be about 160F for no thermal shock.

For below freezing area liveaboard or a boat that gets winter use , there is no finer system..

Our setup is in South FL where the thin often sandy water takes a great toll on an impeller cooling pump service life.

For our style of boating, I am delighted it was aboard when we bought it.

On a newbuild it would be a requirement.
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Old 07-22-2015, 10:05 AM   #23
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There is no extra thermostat on my system. Engine thermostats regulate, they don't just pop wide open when cooling is required.

The muffler should be close to the engine as possible to heat it adequately. A muffler a long way from the engine will also possibly require a resonator. Besides, they are ugly outside the boat.

I don't have soot, or if I do, maybe it lands on your boat? My boat has never had a soot issue.

My exhaust is entirely dry, wrapped with Exowrap. The only salt water in the boat is the genset, installed sometime after the original build.
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Old 07-22-2015, 10:29 AM   #24
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One boat I had two thermostats the rest just one. Up here most work boats that have keel coolers are sized for 80 degree water but our water seldom exceeds 65.
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Old 07-22-2015, 10:39 AM   #25
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You can buy ceramic fiber cylinders that would make very good insulation for a dry exhaust. I used to use such cylinders when I built high temperature (3000F) furnaces. 2" of ceramic fiber insulation and you could touch the outside of the furnace when it was at 3000F.
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Old 07-22-2015, 11:48 AM   #26
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When reading some responses easy to see why wet exhaust became popular nearly a century ago. The white glove trick on the boat deck of a new wet exhaust vessel is revealing.

It just comes down to one's level of soot tolerance and then operating that vessel in such a way to minimize the black stuff. With cars and pickups the regs are in place to entrap or minimize soot. New build boats are on the EPAs radar.

Once into SD hulls forget about keel coolers, hate to rip off a Fenstrum at 18 knots.
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Old 07-22-2015, 12:08 PM   #27
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Michael, is that Dublin as in Ireland? Stopped in Galway once many years ago on a trip around Ireland and up to the Shetlands and over to Norway on an old Boston beam trawler built in 1938 that was left over there after sub patrols during the war. Converted her at Bergen Mekaniske Verkstad to a stern trawler and took her to Alaska. Very nice fishing fleet in Ireland, many more small full displacement boats than over here. I'd love to see pictures of your boat.
Yes indeed - boat is on Shannon - steel - not really a trawler and not very good looking but lots of room and terrific in big inland seas. Getting her ready for sale - too much up and down inside for crocked knees. Going cheap !! M
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Old 07-22-2015, 04:38 PM   #28
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FF- there is no concern about thermal shock with the 80F water coming back into the engine from the KC. No different that a truck with a radiator below freezing or a marine engine with a HX running in winter seas. The water from the cooler, of whatever type, blends with bypass flow at the suction to the circ pump impeller. It is well mixed there, and very little cold flow as tstat is nearly shut.

The little Kubota has a bypass built in between tstat housing and the circ pump housing.

Not a concern.
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Old 07-23-2015, 06:38 AM   #29
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The usual truck (or auto) is set up so the return cooling water is about 20deg cooler than the engine output.

IF the engine mfg has an internal setup that tempers the return water thats great.

But not all do,and the chance the vessel was set up to operate in 80F water and is in 40F water exists..

Next time its cold , notice how many 18 wheelers need to cover most of the radiatorto keep from overcooling.

The bypass thermostat operates in conditioned water and its life is like most other thermostats , quite long.
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Old 07-23-2015, 06:54 AM   #30
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A common method years ago was to install a gate valve in the coolant line to restrict flow, sort of a "manual thermostat", judicious use of the temperature gauge would have been advisable I think.
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Old 07-23-2015, 10:12 AM   #31
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I have dry stacks and fin type coolers for the main, gen. And a/c. The only issue I have Is in slow/no moving warm water. Heat saturation occurs.
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Old 07-23-2015, 10:36 AM   #32
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I assume your talking about running the generator and AC at the dock?
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Old 07-23-2015, 11:32 AM   #33
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Modern diesels are very efficient and have very little lost energy in the form of heat while they are idling. In Montreal in the winter, if I got caught in traffic driving my diesel, I could watch the water temp drop to the bottom of the scale and the cabin heater stopped working until I got moving again. The cooling system was great for hard driving but the diesel did not have enough extra energy to keep itself warm. VW puts "glow plugs" (their term) in the water jacket to heat the coolant electrically so you can have cabin heat.
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Old 07-23-2015, 11:40 AM   #34
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I have no trouble keeping the Cummins running at the correct temperature when the water temperature is 5 degrees or so in the winter or 22 degrees in the summer. I think you are over analyzing the cooling issue. To add a little fuel to the fire, the oil cooler and trans oil cooler have coolant, not salt water, running through them.

Those of you regulars will recognise a pet theory of mine, for those of you raw-water cooled, why not run coolant instead of salt water through your expensive heat exchangers?

A home-made keel cooler might have different issues than a manufactured one.
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Old 07-23-2015, 12:01 PM   #35
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I have a mechanical gearbox with no provision or need for coolant.
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Old 07-23-2015, 12:12 PM   #36
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Those of you regulars will recognise a pet theory of mine, for those of you raw-water cooled, why not run coolant instead of salt water through your expensive heat exchangers?
.
I for one do not ascribe to your theory as it increases the size and cost of the TX and main coolers. Secondly running the gears at temperatures 50 degrees or so below coolant temperatures makes for a cooler ER and happier clutch packs and other internals.

I totally agree on engine oil cooler being coolant cooled. This results in acceptable oil temperatures (plus 180) for those of us who run under light loads.
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Old 07-23-2015, 12:44 PM   #37
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I've been in 40-50F water with a keel cooler for the past few months and the engine temp holds right where it should, regulated by the thermostat. Only as much coolant as necessary diverts through the cooler to regulate engine temp, just like with a radiator. And a keel cooler actually sees much less temp swing than a truck's radiator which can see anything from 110F down to -20F.
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Old 07-23-2015, 12:50 PM   #38
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I prefer a well engineered wet exhaust system with bulletproof back flood prevention. It's the quietest and the cleanest and absolutely as safe as any keel cooled dry stack system, if its done right.

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Old 07-23-2015, 01:30 PM   #39
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No doubt a good wet system can be quiet and clean. I guess it all comes down to how the boat is used and what an owners preference and experience is. I happen to be more familiar with dry from my commercial fishing experience and like to leave my boat in over winter (yes I go boating in the Maine winter). As long as it's safe I think it doesn't matter.
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Old 07-24-2015, 11:13 PM   #40
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Fish53. Only an issue with the a/c. I may increase coolant capacity but I don't expect a cure.
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