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. :-)