Do I need one?

Pleasure Boats and Performance Boats alike: - The size of your boat, motor or propeller, how fast your boat goes or how warm the water is that you boat in, have little to do with how hot your stern drive will get. What does determine the operating temperatures of you drive has everything to do with how you drive your boat. Things like: do you pull water skiers, do you keep the boat on plane for long periods of time, and how long do you stay at full or mostly full throttle? The drive oil temperature depends on the relationship between time and RPMs. Because the temperature increases in a spiraling pattern, cruising at 3000 RPMs for 3 hours can have the same effect as going 5000 RPMs for 15 minutes. So time on plane is just as big a factor as speed. - Some definite signs are: - If there is a continuous need to remove a white chalky deposit from the top half of your drive, it's probably running TOO HOT!!! - 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. Other signs that your drive may be running too hot is a 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, it is 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 enough. - 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. - Drives listed in order by operating temperatures: (Hottest) Bravo III (270 degrees min.) Alpha (all) (265 degrees min.) Bravo II Bravo HP, XR and ZR Drives (due to their performance applications) Bravo I (Coolest) What does a drive cooler do? - Drive coolers distribute a continuous supply of cool water to the top portion of the stern drive. Tests have shown that cooling like this can double the bearing life and service life of the drive oil by lowering an operating temperature of 220 to 350+ degrees Fahrenheit. It prevents oil foaming, the primary cause of oil break-down which can lead to drive failure. It also dramatically reduces the thermal shock that occurs when the hot drive is plunged into cool water every time the boat comes off plane. These conditions exist on nearly every boat, but are especially prevalent in a high performance application where demands on the drive are pushed to the limit. Bravo 3s are the hottest running drive in the Merc. line-up. The gear ratios and the increased amount of mechanism required to spin the two propellers causes excess heat to build up. Under normal operating temperatures, most manufactures recommend that the oil in their drives be changed every 50 hours. For most, 50 hours can be a few weeks’ worth of use. What is thermal shock? - Thermal shock is a condition that exists when metal, or other materials, are heated up and then cooled quickly. The materials expand from the heating process and contract rapidly when cooled. The drive casing is made of cast aluminum which can develop small stress cracks when subjected to thermal shock on a frequent basis. Also, the many bearings and gears inside the drive develop excess wear from the constant dimensional changes that occur during thermal induced expansion and contraction.