On Mar 5, 8:16 pm, Bruce in Bangkok wrote:
On Wed, 5 Mar 2008 09:53:22 -0800 (PST),
wrote:





Well, Steve, the tree I live in is the one behind my machine shop.
The reason that I will not put a wet stack on the boat does, in part,
involve the 488 pounds that the British Company sells them for (I
don't know how much that is in real money, but suspect it is in excess
of $1000US). Secondly, I have a few of the 1.6L diesels in my
inventory, and as I will not water ski behind the boat, I think 52hp
is adequate to my task, and more reliable and fuel efficient to boot
(I've rebuilt ten of these little engines in the past 5 years)...In
fact, if I had one of the newer diesels available to me, I would
still use the 52hp model. As the boat (18' open runabout, aluminum
hull) will be both trailered and occasionally beached on sand bars,
and as I don't want to pierce the hull or transom to build a cooling
system, the close-coupled radiator system mounted on the injector pump
side of the motor looks like a viable method, and the system's entire
footprint will
be less than 32" wide....Oh, did I mention that this was to be a work
boat? What I am looking for is reliability, safety and fuel
efficiency...speed, resale value, and the approbation of the boating
community are not issues.

For what it is worth:

Nearly all of the commercial fishing boats here are powered using a
large truck engine - say 200+ H.P. equipped with a marine gearbox.
Cooling is through a sea water to fresh water heat exchanger using a
centrifugal pump (mounted below the water line) to circulate seawater
and the normal engine cooling pump for the freshwater side. Used
seawater is vented overboard.

The standard exhaust manifold is used connected to a vertical hot
exhaust which normally has a wire mesh protector.

I mention this because fishing boats usually are fitted out using the
cheapest method that works and none of them use a radiator...

Having said that we did have three oil production barges in the Java
Sea and the generator sets used radiators. As these units were
oriented with the radiators pointing outboard and the fans blowing out
they worked pretty well but a radiator does put out a large amount of
hot air.

So... your idea will work but for whatever reason people that use
boats for a living do not to it that way.

In closing, it is pretty easy for any competent welder to make a water
cooled exhaust manifold.

Bruce-in-Bangkok
(correct email address for reply)

It really doesnt take a competent welder to make a water cooled
exhaust, just some time and some pipe. That said, the shrimpers
around here often run a hot dry exhaust with no mufler...much to my
displeasure in the morning as they run by the house at 5AM and I am
trying to sleep. But it does work fine and reliably.

As to the cooling, the radiator idea really stinks. A heat exchanger
is also something that can be manufactured in the garage, its not
rocket science. The keel cooler however is the best idea and they are
used extensively in the shrimping fleet. For a 52 HP diesel the size
if the cooler is not excessive, probably a couple of 1.5" copper pipes
4' long would do the job. But I am not an marine engineer so dont
take my word for the size. I have a 50 HP Volvo Turbo charged 3 cyl
diesel in my 25' Albin and the heat exchanger is very small. I would
adapt one from something else. Just do a search on EBay for "Heat
exchanger" and look for one with a physical size and price that you
like.