We are the Australian distributor for Simrek Corporation. Simrek produces the most efficient drive shower system for your stern-drive (there are plenty of poor imitations) as fitted standard equipment to Fountain and other high performance craft. This is cheap insurance for the hardest working mechanical component on your boat.
The Physics behind a Stern Drive Cooling System:
Where does the heat come from?
Before you can begin to design a stern drive cooling system, you first have to understand what is causing the heat. If you can start a fire by rubbing two sticks together, it must be true that friction causes heat. If the faster you rub the sticks together the more heat you create, then it’s the speed or the RPMs, which is causing the greater heat. How does that equate to a stern drive? There are many heat sources including clutches and universal joints, but most of the heat is caused by the bearings which allow the shafts to spin. On the top half of the drive, there are two main bearings, one at the front, and one at the top. They share an equal load with one exception; depending on the type of drive you have, the front bearing is spinning 1.5 times to 2 times than the rest of the gears. It doesn’t take a physics professor to figure out that most of the heat generated by a stern drive comes from the FRONT Bearing. This led us at Simrek to ask, if the front bearing is responsible for generating 1.5 to 2 times the amount of heat of the top bearing, why do most drive cooler manufacturers only cool the top of the drive when the sides of the upper gear-case are the hottest area.
What should you be cooling and why?
The component inside the stern drive that is most susceptible to abuse from heat is the oil. It begins to break down at about 300 degrees. The metal components inside the drive can reach temperatures of at least three times that amount before they become affected. The only way the drive components can reach those temperatures is if the oil has broken down and the heat generating friction builds up. If you cool the oil and keep it from breaking down, it will cool and protect the components inside the drive. Now you should be asking, why do most drive cooler manufacturers target the top bearing cap? There is still one more reason to ask the same question.
What is the best way to cool the drive oil?
Think of it like this; if you wanted to boil water in a pot, would you rather use a pot that is one inch thick or 1/8 of an inch thick. Obviously the water would be heated much faster in the thinner pot. The same principals are true when it comes to cooling something. The top bearing cap is over an inch thick, the sides of the drive are less than 1/8th of an inch thick. The thinner the material, the easier it is to wick the temperature of the drive oil inside through the casing. So the most efficient cooling system would be one that targets the sides of the drive. So again, why do most drive cooler manufacturers target the top bearing cap? The other component that is critical for cooling the drive is the amount of water the system can process and apply to the drive casing on a continuous basis.