Just to finish up the story...I acid washed the heat exchanger
with one gal of muretic to 4 gals of water
...took the hx off the boat (tough to do on the Gulfstar
37)..used eye, hand protection with running water
nearby just in case...dipped it in the mixture for maybe 5 minutes total, which removed all the deposits and old zinc residue and whatever...rinsed in fresh water, then bucket of water and baking soda to totally neutralize any acid...painted with ford blue paint
(close enough). Back on the engine
, usual struggles with getting all hoses connected while working in a space you would have to be three feet tall to work in correctly...got new end cap and gasket
from TAD, very friendly people, give them a call if you need anything. Run at dock
now up to 2000 rpm
, never goes over 180. It is a lot of trouble to remove the hx from the transverse mounted ones in the Gulfstar
, but it is the best way to make sure the heat exchanger
is not the problem.
There really didn't apprear to be any blockage, but there was a lot of bubbling initially, so there must have been a lot of carbonate buildup from the seawater that was making the difference...when I ran it at dock
before at same rpm
, would slowly overheat...
Did have the usual air block problem common to Perkins
when putting fresh coolant
into the engine
, you have to fill it up, run it a minute or three, and then check the coolant
level in the header tank again...it will usually hold another half gallon or so...if it is not right, you will get an overheat signal very quickly as the temperature sensor will be reading steam temperature, not water temperature..
anyway, worth the effort if you have the typical overpropped, overheating perkins
in an older sailboat...do it before you start tearing into thermostats, temperature sending systems and replacing pumps...although replacing the pump on an older engine usually helps. Mine is fine, the water dumping out the back of the boat at the dock with the rpm at 2000 is barely warm now, so removing the flow restrictions through the hx definitely helps.
NOTE: THE ACID WASH TECHNIQUE IS DANGEROUS. DO NOT USE THIS IF YOU ARE NOT SURE OF WHAT YOU ARE DOING, AND USE EYE, BODY, AND HAND PROTECTION...ALSO, WHEN YOU DISPOSE OF THE ACID WATER MIXTURE, MAKE SURE TO NEUTRALIZE THE ENTIRE 5 GALLONS WITH BAKING SODA TO THE POINT THERE IS NO REACTION...THEN USE LOTS OF WATER TO DILUTE..DON'T JUST DUMP IT ON THE GROUND OR IN YOUR PLUMBING