Drive Showers FAQ'S

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Drive Showers

1. Do I need  a drive shower?
2. What does  a drive shower do?
3. What is thermal shock?
4.  Why a Multiport Drive Shower®?
5. What about the other drive showers
6. What kind of temperature reduction will I get with a Simrek Multiport Drive Shower®?
7. Why doesn't MerCruiser put them on their drives as standard equipment?
8. Do I need the 90 Degree Pick-up Ports?
9. Will the Multiport Drive Shower® cause drag and slow my boat down?
10. Do the stock bolts on the drive require a special wrench?
11. I have Latham (or Imco) Steering and I want to install a Halo. How do I remove the stud?
12. Will a drive shower void my warranty?
13. What about Drive Coolers that target the top cap but also force the water down the sides?”

1. Do I need a drive shower?

According to the certified MerCruiser Master Technician that Simrek contacted,  "every boat should have a drive shower." There are two obvious signs that your drive may be running TOO HOT:

A. If there is  a continuous need to remove a white chalky deposit from the top half of the stern drive.  The white chalky deposit means that the outside casing of  your drive is running 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 your drive.  The hotter the drive, the more deposits are collected, and they harder they are to remove.

B. Other signs that your drive may be running too hot include 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's  the 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.  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:

- Bravo III (270+ degrees)
- Alpha (all) 265+ degrees
- Bravo II
- Bravo HP, XR and ZR Drives (due to their performance applications)
- Bravo I

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2. What does a drive shower do?

Drive showers 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 a minimum of 30%.  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 is especially prevalent in a high performance application where  demands on the drive are pushed to the limit.   Under normal operating temperatures,  most manufactures recommend that the oil in their drives be changed every 50 hours.  For some, 50 hours can be a few week's worth of use.

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3. What is thermal shock?

This 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.

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4. Why a Multiport Drive Shower®?

The Simrek Multiport Drive Shower® System utilizes two pick-up ports for twice the water volume than any other drive cooling  system available. It is also the most efficient because it targets the top and  two sides of the drive.  All the other cooling systems available target only  one surface of the drive with one dump port.  Drive shower systems that only spray water on top of the drive are less efficient because they target the bearing cap on the top of the drive which is over an inch thick.  The sides of the drive are less than 1/8th of an inch thick and offer much less resistance to temperature  change. They are also the only drive cooling system to utilize the 90 Degree Pick-up Port System.

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5. What about the other drive showers, including knock offs that don’t require drilling?

There are two designs of shower systems targeting the top bearing cap.   One is a solid tube design, the other is a flexible tube design with and without a bearing cap plate.  At first glance, both would appear to cool the sides of the drive simply because the water will run down from the top.  Consider these two conditions:

The solid tube system sprays water at the top surface of the drive from a 1/2 inch diameter tube which is located at a 90 degree angle to the top of the drive, and about 1/2 inch away.   Try this experiment at home: turn a drinking glass up side down, and hold it under your faucet approximately 1/2 inch away.  Now turn the faucet on full force.    You will probably find that every thing in the room is now soaking wet, (including yourself --- sorry about that!), except the sides of the glass are  still dry.  This is due to the force and velocity that the water is under as it exits the faucet.  The same principles hold true in the case of a drive  shower.

The flexible tube system  with an optional bearing cap plate directs the water at the top bearing cap at  almost a 180 degree angle.  This causes the water to skip over the top of the drive and exit out the back of the plate on to your transom.  This is a great way to wash your transom, but not a very efficient cooling system for your drive.  Try this experiment at home: turn a kettle up side down in your drive way. (This time I promise you that you won't get wet.)  Hold a  garden hose, at an angle a little more than horizontal to the ground and about  an inch away from the kettle.  Open the spray nozzle to full force.   You will probably find every thing behind the kettle is soaking wet, but the sides of the kettle are still dry.

With the force of the water that is traveling through a 1/2 inch diameter tube at speeds equal to the that of the boat, it is easy to see that this water will only go where it is aimed,  and gravity will have little influence on its path.  Through the use of multiple  dump ports aimed at the top and both sides of the drive, the Simrek System delivers the cooling water under less pressure, which allows it to spend more time in direct  contact with the side surfaces of the drive.


In the recent past, there have been numerous attempts to not only copy the design of our driveshowers, but to get around the US Patent that was issued to us for the innovative design our 90 degree pick-up ports. This is just another one of the latest attempts to do so. The concept of not having to drill any holes in the anticavitation plate is appealing, but it does have its drawbacks. When we originally designed our drive showers over 6 years ago, we utilized a Computer Assisted Design Program call Pro-E. We explored the idea of coming up with a design that would be mounted to the drive without drilling any holes. We ran the stress analysis package of Pro-E against a similar configuration to the drive shower shown above. The results told us that the shear load produced by water flowing at just over 64 MPH. would be equal to the same force that we now use to form the tubing into our drive showers. At just over 40 MPH, the force produced by the water pressure is enough to deflect (flex) a .500 inch OD X .403 ID 316 SST tube by 5.263 degrees for every inch of unsupported tubing exposed to that water flow. It doesn’t sound like much deflection until you start multiplying it by 10 inches.

The Trigonometry formula goes like this: .0175 per degree per inch. Or .0175 X 5.263 degrees X 10 inches = .921. That’s just under an inch of deflection when 10 inches of unsupported tube is exposed to the pressure of water that is traveling at 40 MPH.


I took you through the physics and trigonometry, in order to show you one of the reasons we originally rejected this design. We felt that the pick-up ports would be deflected upwardly enough to render them unable to supply a continuous flow of water to the top of the drive. Then when the water pressure falls low enough, the tube would return to its original form. Unless you were watching the shower while the boat was underway, you would never know if it was working or not

A recent posting on EBay for one of these showers had a description as follows: “This drive shower was purchased at the end of 2003. After installing it onto my Bravo 1 drive and running it twice on the lake I decided to upgrade to an IMCO XR drive which comes with its own drive shower.” This is the picture that accompanied the description. Notice that after being used only twice, the tips are already bent.


6. What kind  of temperature reduction will I get with a Simrek Multiport Drive Shower®?

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The most recent testing was done by Jim Wilkes for Hot Boat Magazine, and published in the April 2000  issue.  Dockside magazine also tested the Summit Design and found a 50 degree  drop in drive operating temperature and published their findings in the August 1999 issue.  They also did a side by side comparison between the Summit Design  and the Halo Design and found the Halo to cool the drive by an additional 8 to  10 degrees.  Testing was also performed by the United States Customs Service.   They found a 50 degree Fahrenheit drop in temperature. 

Gene Weeks of Team Lazar  did a side by side comparison between an Imco Power Shower and a Summit Multiport  Drive Shower®, and found the Multiport system to cool the drive by an additional  15-20 degrees over the Power Shower.

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7. Why doesn't MerCruiser put them on their drives as standard equipment
Simrek feels that MerCruiser makes the finest stern drives on the market, but they are in business to make a profit.

In order to incorporate a cooling system into the stern drive they would have to make major changes to the castings that make up the upper portion of the drive.  While some changes  have been made to the internal components, the castings for both the Alpha and  Bravo uppers have not changed since they were first introduced.  Adding a  cooling system would require a major redesign of multiple castings at a substantial cost.

MerCruiser is also in the repair parts business.  There is a term used by manufacturers called "planned obsolescence."  If a product lasts too long, there will  be fewer repeat sales or repair part sales.  That is why no one sells a light  bulb that doesn't burn out eventually.  Unfortunately for Simrek, the Multiport Drive Shower® has no planned obsolescence.  We do not sell repair parts because  there is no need for repair parts.

In the article "Way to cool" that appeared in Poker Runs of America Magazine, Editor Peter Tasler asked Mercury  Racing why they didn't install drive showers as OEM equipment? There response was, "Mercury Racing designs its drives to handle a certain horsepower range and the temperatures associated within that range, in typical boating environments."

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8. Do I need the 90 Degree Pick-up Ports?

If your boat requires you to trim your drive near of past vertical while you are performance boating,  then your drive cooler is probably not picking up any water.  The Pick-up Ports of all drive cooling systems offered today consist of a tube mounted through  the cavitation plate at a 90 degree angle and cut off at a 45 degree angle.   This means that the tube is being dragged through the water at a 90 degree angle when the drive is trimmed to vertical.  When you trim the drive out further,  the tube is facing away from the stream of water.  Under these conditions the Pick-up Ports will fail to supply the cooling system with enough water to  adequately cool the drive at a time when they are needed the most.  This is not a smart design.

When we first introduced the Multiport Drive Shower®, we thought the problem with existing cooling systems was primarily  in the water delivery system.  We addressed that issue and have since identified the opportunity of maximizing the pick-up system. Independent testing verified this, and because the improvement was so great, we decided to apply for a US Patent.

The 90 Degree Pick-Up Ports that Simrek offers exclusively to Multiport Drive Shower® customers provide a continuous supply of cooling water at any  trim level.  Because the Pick-Up Port faces forward into  the stream of water going under the cavitation plate, they scoop more water than the conventional 45 degree ports.  Instead  of failing during performance boating, they are actually at maximum efficiency.


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9. Will the Multiport Drive Shower® cause drag and slow my boat down?

The pick-up hole makes up the majority of the small 1/2 inch diameter tube that  is exposed under the cavitation plate. Because the water is only being  re-directed, instead of being forced to build back pressure (as it does in the case of a speedometer pick-up) no speed reduction will be noticed. The Multiport Drive Shower® is used on a large number of race boats. Race teams measure their boats speed in tenths of a mile per hour. If the drive shower caused any loss in speed, they would know about it and remove it without  hesitation.

10. Do the stock bolts on the  drive require a special wrench?

The stock bolts on the drive can be removed with a standard 3/8 - 12 point socket.

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11. I have Latham (or Imco)  Steering and I want to install a Halo. How do I remove the stud?

If you are installing a Halo on a drive with Latham or Imco steering; To remove the top left stud from the drive, use a separate nut (3/8 x 16) as a jam nut. Tighten the two nuts together so that you can place a socket over the jam nut and onto the original nut. Loosen both nuts at the same  time. The stud is not Loctited in, and should come out easily.

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12. Will a drive shower void my warranty?

We developed our new “No Drilling Mounting System” as a result of MerCruiser’s new policy regarding damage to the finish on their new drives voiding their Corrosion Warranty. When asked about drilling holes in the drive to mount a shower, Rick Lang at Mercury Marine replied, "If an aftermarket component causes a failure, or in this case leads to corrosion damage... our warranty will not cover the damage/failure". Also, for SeaCore product "under no circumstances should the surface of the finish be damaged or it will corrode and there will be no warranty".

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13. Coolers that target the top cap but also force the water down the sides

If you wanted to cool a glass of water you would be better off putting it in the freezer than in the refrigerator. The same is true of cooling your drive, the colder the water the better. Why would you want to pre-heat the water by first passing it over the top bearing cap?

Anytime you force water into a chamber, as many cooler do, you will “break its stream”. Anyone who has used a garden hose has seen the effects of streaming. Once water has taken a shape it has a tendency to retain that form. That’s why the water from a hose keeps the shape and diameter of the hose until gravity or some other force interrupts it. Once the water is inside this chamber and is forced to exit through a hole or series of holes or even simply by turning 90 degrees and then downward by 90 degrees, the flow has been interrupted twice. This is called “resistance to flow” or “back pressure” and reduces the amount of water that the system can process. The smaller the water flow, the less efficient the system will be at cooling the drive and if enough back pressure is created, the pick-up port may cause enough drag to slow the boat down.

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