My Perkins 4.154
has been running hotter in the last several months. It used to run at about 180 - 185 at about 75% load (1800 rpm
? the tach is fairly squirrely), maybe push 190 when I pushed the engine
harder to fight a current
or make a bridge opening or anchorage by nightfall.
In the last couple of months, with lots more motoring than normal (we have put just over 300 hours on since early March 2011), the operating temps have climbed so that I can't run over about 50% load without the temp climbing over 180, and it gets up to 195 or so - very close to 200 - if we increase RPMs over 1800.
I have just flushed the raw water
side with a circulating solution of Ospho (phosphoric acid) using a bilge pump
(see this link heat exchanger cleaning
for the method), and no change when I ran it - still heats up to near 200 when I load it up to cruising RPMs and higher.
I understand the normal range is 169 to 197 degrees, but I hate being on the hottest side of the range, and the fact that this is worsening over time indicates something.
I have not replaced the thermostat yet - do they go bad in a way that allows slowly increasing engine
operating temps, or do they just go all the way bad?
Thanks in advance,