cooling

[jrgntheoc]

have got an atomic4 gas in a cat 27. i just replaced the water pump impeller and she seems to be running hotter than before the replacement. She's hovering at 160 degrees and I'm wondering if that's normal. I just bought the boat a couple of months ago.

[Rocketman]

When you replaced the impeller, was any of the ruber paddles missing? If they were then you need to find them, they will plug up the heat exhanger and not alow water to flow. When I bought my boat, they fist thing I checked was the impeller, and it was missing a paddle, so I opened up all lines that lead to the heat exchanger and found 20 or more old broken impeller paddles that were completely plugging the heat exchanger.

[Sailmonkey]

Originally Posted by jrgntheoc

have got an atomic4 gas in a cat 27. i just replaced the water pump impeller and she seems to be running hotter than before the replacement. She's hovering at 160 degrees and I'm wondering if that's normal. I just bought the boat a couple of months ago.

Is this engine raw water cooled or fresh?
Great engines, but they tend to clog up with deposits after a few decades. When I had one it ran hot, My cure was to remove the exh manifold and head, clean out the passageways and reassemble. No further problems.

[jrgntheoc]

thanks for the replies guys. there were no missing impellers when I changed it. its raw ocean water cooled. does running at 160 degrees seem hot to any of you?

[Rocketman]

160 degrees seems a little high but it may not be, to determine what it should be you can take out the thermastate, put it in a pan of water, heat it up on the stove with a thermometer, and watch it. when it starts to open record that temp when it is fully open record that temp. The temp that the engine will normally run with that thermastat is somewhere in the middle. Someone may have replaced the thermastate with a hoter one to get water in the water heater hotter.

[Rocketman]

Your desiel engine running at 160 will not hurt it. If it goes to 180 or above I would have more concerns, the other obvious causes for over heating is a fouled prop. But of course this would only happen while underway.

[GordMay]

Greetings and welcome aboard the CF, jrgntheoc.

Normally a sea water cooled Atomic 4 is operated between 140° and 160°, whereas a fresh water cooled A-4 runs at 180 to 190 degrees.

With a raw water cooled A-4, running it at above 135-140 degrees will cause the promotion of salt crystals to build up in the engine cooling passages. This in turn will cause a blockage of coolant flow, which promotes overheating.
Fill the block with white vinegar (or muriatic acid) and leave it there for 24 hours, which will break down any salt crystals in the block.

See ➥ http://l-36.com/Atomic4/a4manual2.pdf

And ➥ Cleaning an Atomic 4