T&T: Detroits, impellers and keel-coolers

[John Tones]

Truelove39@aol.com wrote:
> I can't see the sense of going to a dry exhaust simply on account of
> eliminating impellers. Impellers, like other nondurable parts, are  fine if
you
> simply change them, before they fail, at scheduled  intervals. Keel cooler
> installations of the protected, Fernstrum-type  or better, a simple split
pipe or
> channel welded to the shell plating make  a lot of sense on a steel boat.
But I
> wouldn't have one on a 'glass boat because  I don't think they can be
adequately
> protected.
>
John et-al
> Well I am sorry to dissagree with your take on the keel cooler portion of a
dry exhaust system. The keel cooler on our boat has been functioning for about
30 years with no mention in the log book of it ever having been repaired or
replaced. Now this is in the PNW where we only have drift wood and dead heads
and no Manatese etc to run over but I think the idea that the keel cooler is a
vulnerable item stuck on the outside of the hull is very much exagerated. Our
cooler shows no sign of ever having been hit, and it is basically just four
copper pipes about 10 ft. long, but yet I am repeatedly having to clear the
crud (sea weed, plastic bags etc)picked up by the inlet thru hull for the
head. I always think while cleaning this thru hull how lucky we are to not be
drawing the cooling water from the sea. I have looked at many vessels with wet
exhaust systems and they all appear to me to take up much more room with the
muffler and pipes than our dry system does to say nothing about being more
complicated. With our system, the only impellor in the cooling system is the
cast steel one on the engine and it is running in an anti-freeze water mix so
there is no corrosion to worry about.
I will agree that with some vessel designs there is not really room to
pass the dry stack / trunk through the cabins but with a new
construction it would not take much thought to provide for the space. I
like our dry system but don't really care what you have on your boats as
its every ones privelige to make their own decision.
Just another Canuck thought train <grin>

John Tones  "Penta"
Sidney, BC