The white chalky deposits mean that the casing of the drive is hot enough to boil off the water that is splashed onto it. This boiling process turns the water into steam and leaves the mineral deposits behind to bake onto the drive. The hotter the drive, the more deposits that are collected and the harder they are to remove.
This is what some of our customers said regarding this problem:
Other sign that your drive may be running too hot is paint discoloration, or a cloud of steam that appears every time your boat comes off plane. Unless you have opened through hull exhaust, what you are seeing is not exhaust, its steam that is generated when a hot drive is plunged into cool water. This process of heating and rapid cooling is known as thermal shock and can be detrimental to metal components, especially aluminum, if the range is extreme.
Keep in mind that however hot the casing is, the components inside are running much hotter. Published test results show that some stern drives components operate in excess of 350 degrees F. If you are experiencing any or all of the above conditions, your drive is probably operating over 250 degrees. For the same reasons that automotive engineers established approximately 200 degrees as an optimum operating temperature for their engines, most marine experts agree that this also holds true for stern drives. Even MerCruiser will admit that 300 degrees is flirting with disaster. That's the temperature at which the oil begins to foam and break down. It loses the ability to lubricate the components inside the drive, causing them to freeze and destroy the inside of the drive. It is commonly referred to as “the drive grenading”.
Simrek Corporation specializes in external stern drive cooling systems for your high performance or pleasure boating needs. Composed of high-grade stainless steel, the Simrek Multiport Drive Shower® can add years of life to your Alpha and Bravo drives