Corrosion has caused the paint to flake off around the base of my raw water pump. There is no apparent leak and the impeller and top seal are in good condition, I don't know how the shaft is sealed. My zinc was almost totally dissolved. Is this just galvanic corrosion and I need to change the zinc more frequently, or is there a pump shaft seal that I need to change? There is no other corrosion or leaks visible. Beta 38, 2013 model.
If the raw water pump had a bad seal, you would see an obvious water leak. Please post a photo so we can see what the problem is. Without this I really cannot comment as to whether this is galvanic corrosion or---?
These engines have a fairly small zinc anode which is best checked every 3 months if you are in a marina. You will get 6 months from one if you are at sea or away from shore power and the influence of other peoples boats.
Here are some views of the pump corrosion. I have changed the impeller but it does not seem to be pumping as much water as usual and it is exhausting a lot more water vapor than usual. Do I need to take the heat exchanger apart to look for an obstruction? Or check the line to the vacuum breaker and then to the high-rise exhaust for bits of zinc?
That corrosion is a new one on me. I would ask Asa to check this out and report.
The extra vapor that you are seeing is most likely due to the ambient temperature being so cold that the slight warming from the exhaust cooling water is producing the extra vapor.
Started the engine yesterday and had no cooling water flow except down the front of the engine. Found a total blockage in the junction between the raw water pipe over the top of the engine and the rear heat exchanger manifold. The plug of corrosion/salt extended into both the tube and the manifold, but beyond the plug the tube, manifold cover and heat exchanger tubes were clean. The copper tube and bronze? manifold cover had been touching. When I reassembled them I left a small gap.
I don't know what the "salt" is, I will have a chemistry professor friend analyze it.
The over heating and extra water vapor were apparently early symptoms of restricted cooling water.
The engine is running perfectly now - though I need to order a new heat exchanger manifold screw, I had an M6 the proper length but it is phillips head and probably not torqued properly though it doesn't leak.
I am very pleased that you found that.
We do have the correct screws in inventory. They have a special plating so that they do not react with the aluminum manifold.
