Not long ago we had a guy post that his Perkins was running progressively
hotter.

Consistent with my program of swapping out the oldest peripheral part each
year, today I yanked off the 22 year old heat exchanger and replaced it with a
new one.

I found out there are two heat exchangers for the 6354, one that extends 14"
from the expansion tank and one that extends 9.5". The turbo models are
supposed to use the 14", but mine was originally plumbed for the 9.5" and has
been running well within specs at all times. I stuck another 9.5" on, rather
than start reinventing the plumbing. The 14" would also have extended across
the front of the turbo-intake screen, although about 7-8" away, and I wasn't
entirely convinced that might not have an effect on air flow.

I had been running about 10-15 degrees hotter this summer at speeds above 1800
RPM. Not only was my heat exchanger ready to be replaced, (the local Perkins
guru says the life expectancy should be 10-15 years), but a couple of chunks of
pencil zinc had fallen off the zinc nuts in the past, and were laying across
the raw water inlet. Probably explains why I was running hot at high RPM,
inadequate raw water cooling flow.

Anyway, the job was very easy. I'm the world's worst mechanic, and it took me
under two hours start to finish using a $49 socket set. We're heading north in
about a month, and that will takes one more thing off the "to do" list before
we go.
If I still own the same boat in another 15 years, I won't hesitate to swap the
heat exchanger again. :-)

"Gould 0738" wrote in message
...
Not long ago we had a guy post that his Perkins was running progressively
hotter.

My brother has two perkins diesel fresh water cooled engines. His also
overheat at RPM's above 1800. We have traced the problem to obstructions in
the raw water cooling. Specifically the transmission cooling. I'm trying
to get him to reroute the fresh water through the transmission with possibly
a partial bypass. This will keep the iron in the transmission from
corroding shut and increase raw water cooling.

Have you guys ever wondered why there isn't a fresh water flush built
into these systems?

This stuff doesn't corrode in the short time it's running. It
corrodes like this sitting there with salt in it...duhhh..

It would be SO simple to connect a flushing valve from the boat's
fresh water system to the salt cooling system and flush the salt out
of it right after the engines were shut down, then close the seacocks
to keep the salt out of them, wouldn't it?

Hell, for what these boats cost, it could be solenoid operated valves
with a pushbutton by the key saying "FLUSH" like the commodes!



On Tue, 19 Aug 2003 08:18:02 -0400, "Jeff Rigby"
wrote:


"Gould 0738" wrote in message
...
Not long ago we had a guy post that his Perkins was running progressively
hotter.

My brother has two perkins diesel fresh water cooled engines. His also
overheat at RPM's above 1800. We have traced the problem to obstructions in
the raw water cooling. Specifically the transmission cooling. I'm trying
to get him to reroute the fresh water through the transmission with possibly
a partial bypass. This will keep the iron in the transmission from
corroding shut and increase raw water cooling.




Larry W4CSC

Maybe we could get the power grid fixed if every politician
regulating the power companies wasn't on their payrolls.

Have you guys ever wondered why there isn't a fresh water flush built
into these systems?

This stuff doesn't corrode in the short time it's running. It
corrodes like this sitting there with salt in it...duhhh..

The problem isn't corrosion, per se. The heat exchanger is a bundle of bronze
tubes, and the expansion tank is aluminum (the better to radiate heat). Stuff
just gets plugged up and weak after a couple of decades. Recommended service
life is 10-15 years on the heat exchanger, and mine had served well over 20.
Just think, if I had a gas engine, even running exculsively in fresh water, I
would have been replacing the entire engine......for the second time. :-)

Corrosion only requires:

Anode
Cathode
Electrolyte
Path

Anode = Aluminum
Cathode = Bronze
Electrolyte = saline
Path = metal-to-metal

The idiot that designed this system could not possibly have created a
better battery -- spell that corrosion -- if he/she tried.

This is a recipe for sure and scientifically verifiable premature
failure.

--



Grady-White Gulfstream, out of Southport, NC.

http://myworkshop.idleplay.net/cavern/ Homepage
http://www.southharbourvillage.com/directions.asp Where Southport,NC
is located.
http://www.southharbourvillage.com/autoupdater.htm Real Time Pictures at
My Marina
http://www.thebayguide.com/rec.boats Rec.boats at
Lee Yeaton's Bayguide



Zinc anodes have prevented any serious corrosion on this unit since 1982.