by John Barr
What would you think of a product that could save your boating vacation and thousands of dollars in the long run. No, wer’e not talking about investing in hi-tech stocks. We're talking about a remarkable product that can be installed in minutes and is maintenance free.
Most skippers are well aware that stern drives take a lot of abuse. Operating in the most hostile environment known to man and in outrageous conditions, they are subjected to high torque loads for hours on end. Just imagine the loads and forces involved when a drive comes out of the water and unloads, then plunges back into the water where the prop bites again, occurring over and over as in racing conditions. Ah, you may say to yourself, that's racing.
But think what happens to the drive on your own cruiser. First off, to get your vessel on plane you're putting 300 hp and 250 ft lbs. of torque through a 90 degree turn down a shaft to another 90 degree turn out to the prop. Then you cruise for hours with the hottest part of the drive, the bearing cap, out of the water. Hot exhaust is going through the drive with only 3 quarts of oil to cool it. Like some kind of torture test you plunge the drive back into cold water as you come off of plane. To say that these drives are an engineering marvel is certainty an understatement, but when you consider that this torture test occurs over and over on a given weekend, it's an absolute miracle they survive at all.
Hot Stuff
With all this considered, the greatest enemy of the modern stern drives is heat. Most stem drives manufacturers are aware of this problem and have developed special lubricants to combat the effects of heat and the resulting break down of lubrication protection. Even so, drives still fail. So the logical conclusion is that if we can control the heat, our drives should last much longer. The problem is twofold - (1) the heat produced by the drive and (2) the sudden immersion of the drive into cold water as you come off of plane. The cast aluminum alloy which is used in the modern stern drive does not respond favorably to the expansion and rapid contraction caused when a super hot drive is plunged into cool water. This thermal shock condition is especially prevalent in high performance applications where demands on the drive are pushed to the limit. Indicators that your drive is operating on the edge are a white chalky deposit on the top half of the drive housing or steam generated off the transom area each time the vessel comes off plane.
Solutions
There is a simple affordable solution. It's a drive shower. Drive showers have been around for decades and are utilized with great success on everything from houseboats to high performance off shore racing boats. The operation is simplicity at its best. The drive shower routes cool water from below the cavitation plate up to the upper bearing cap where the majority of the friction or heat is generated. By reducing the temperature of the drive it further reduces the possibility of foaming and thermal breakdown of the oil which will certainly lead to drive failure. Easy to install, this product could add years to the life to your stern drives.
Unique Design
The Dockside Test Team has tested and used drive showers for years, but now there's a new twist. Drive showers on the market today all use one intake and a delivery tube that picks up raw water from below the cavitation plate and dumps cool water on the drive. These showers are simple, very efficient and effective, and our own tests have shown that they can reduce oil temperature as much as 30 degrees under most conditions.
Recently we discovered a drive shower that takes this simple process and doubles its effectiveness. The Summit and the new Halo design drive showers by Simrek Corp. expand the theory that if one is good, two has got to be twice as good. Their unique design utilizes two intake ports for more water volume and up to eleven dump ports for more uniform distribution on the top and sides of the drive. By using a more even distribution of the cooling water and more water volume, in theory the drive should run cooler than a drive utilizing the traditionally designed drive shower.
Putting it to the Test
Since the test team's 300 SeaRay was not equipped with drive showers and we were experiencing symptoms which would indicate drive overheating, we were excited to test the new Summit drive showers. These new showers are manufactured of polished 304 stainless steel and come complete with top quality stainless hardware and first class instructions and templates.
Our vessel is equipped with twin 5.7-liter MerCruiser Alpha 11 drives. First, we temporarily installed our Gear Smart temperature sending unit on the- port drive and at the same time made certain the oil level was correct. We then cruised out past the breakwater until the drive was up to operating temperature. We made two wide open throttle runs in opposite directions to establish our base line. The results of this test recorded a peak drive temperature of 218 to 237 degrees Fahrenheit. With our base line established, we installed the new Summit drive shower. Although our vessel was in the water, we were able to install the shower in approximately 30 minutes. Installation was simple and straight forward and could be performed by any skipper with average mechanical ability. Be certain that you use the template supplied by the manufacturer before drilling your cavitation plate and check it twice. One important word of caution: Since our vessel was in the water, we used a 9 volt cord less drill when performing this installation. By all means do not use a 110 volt drill near the water. Injury or death from electrical shock can occur.
After the installation we duplicated the first test. To our amazement, the peak temperatures had dropped to 187 degrees. This is a drop of 50 degrees and well within the drive's, and our, comfort zone. We were so amazed that we performed the test again, just to be sure. Again, the temperature had a significant drop. Though not as much of a drop as in the first test, it was a considerable drop all the same. in speaking with an engineer, he stated that the reason we did not experience the same amount of drop was undoubtedly because of a phenomena called heat saturation.
Seeing is Believing
We were believers and installed the second Summit drive shower on our starboard drive. since we experienced such a significant drop in temperature over the conventionally designed shower, we can conclude that Simrek's theory of two being better than one is right on the money. But we're not the only ones convinced by Simrek's technology. The Multiport Drive Showers® have been tested by and are now original equipment on Carrera Boats, Fountain Powerboats, and Talon Marine Boats.
Reprinted with permission from Dockside - August, 1999.