J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Engine Cooling Problems Revisited

In one of the past forums, I reported intermittent cooling water flow. Since then I have isolated the problem. It is due to rust inside the engine cooling passages (raw water cooled combined with never-replaced zincs). I created a flush kit and back flushed the engine several times, getting lots of small rust flakes and particles. Things are working much better now but I know the problem is not gone.

Does anyone have any experience with descaling acids? A book I have by Nigel Calder suggests a product called Saf Acid. In lieu of that, he suggests Oxalic or Phosphoric Acid. I am having a hard time finding a source for any of these acids.

A warning: do not use vinegar. A friend suggested using vinegar to dissolve the rust. I tried it on the thermostat housing. It actually dissolved the cast iron as well as the rust. The threads pulled right out with no effort at all.

Comments?

We were having intermittent shut down, inability to run the engine over about 2000 rpm without choking and much black smoke. The exhaust elbow was plugged from 16 years of short time running under light loads. Replacement has done a world of good.

On related note an owner reports: "On survey we discovered considerable wetness in the hull, starboard aft quarter emanating from the exhaust outlet. You might want to alert your members of the importance of maintaining the caulking around the exhaust tube where it exits the hull. I checked several other J-30's with a moisture meter and found, without exception, had similar problems. The degree of migration of the water in all cases was significant, often as far forward as the aft end of the keel."

I've found that there are a couple of things that can cause intermittant cooling water flow. Here are some things to check for: Make sure the cap to the seawater strainer is well sealed. The pump can suck air from a poor strainer seal. On the Perko strainer, it can be tricky to screw it down level, and the gasket is cork and after years doesn't seal as well. Also, check for wear in the water pump housing and the little cam that compresses the impeller blades. It is easily replaced and wear reduces the pump's effectiveness.