This letter is in response to your inquiry regarding the performance of the drive showers which my agency purchased for performance testing.
The shower was installed on a 42' Fountain Lightning with 502 EFI engines and Bravo 1 outdrives. Only one shower was installed on one outdrive and both outdrives were equipped with temperature gauges, with sensors in the oil filler holes.
After approximately five minutes of operation at 4500 RPMs, the outdrive without shower registered 190 degrees. The drive with the shower failed to record the minimum gauge temperature of 140 degrees. The gauges were reversed to make sure that there was not a gauge failure. The same results was obtained.
Based on this single test, I found that the use of the shower results in a sensor reading indicating a reduced oil temperature of at least 40 degrees and possibly more. How this finding will effect the life of the outdrive unit is difficult to determine. However, I do know that the enemy of moving parts is heat and I have every reason to believe that the shower significantly reduces this problem. It therefore stands to reason that we can expect a proportional increased life expectancy for our outdrive units.
I hope that this letter answers your questions. If I can be of further service, please contact me at your leisure.

(signature removed for security purposes)

Benjamin A. Rich, Special Agent
Program Manager

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.

As everyone says, its worth it just for not having to clean the drive very often. I do think they drop the oil temp though.

We installed a Simrek drive shower in 1999 while racing APBA Factory 1.
F1-51 ONE VISION Racing.
We lost no measurable speed
We never lost a drive.
I still run the same drive with the same Simrek drive shower
Mike "Gordo" Gordon

I'm still trying to understand how these drive showers can cause prop cavitation. Over the winter I intalled the Latham showers on my outdrives. Haven't run them yet, but now I am wondering about cavitation. The Latham shower has one intake mounted through a 3/8" hole drilled on the port side of the cavitation plate with the right hand swinging prop. It is a couple inches behind the prop and about one inch from the back of the cavitation plate. Can this cause cavitation and, if so, how?

There is a low pressure area on the bottom of the cavitation plate during startup, and it just sucks air down the tube. There must be some backflow along the surface of the cavitation plate toward the inducer side of the prop to draw air forward.

Michael

Michael1 above is correct. There is a low pressure region being created by the prop, predominantly on the face or forward side of the propeller.

To go a little further-
Cavitation is an inverse function of fluid density (among other things, but density is what we're concerned with here). Increase in density, decrease in cavitation. Decrease in density, increase in cavitation.

As air is sucked down the drive shower by the low pressure region created by the propeller, it mixes with the water around the propeller, creating a water/air suspension mix that is less dense than water. This decrease in density increases the likelihood of cavitation. In your case this is what is happening. The prop spins faster than it should if it were in "solid" water.

Others that do not have this cavitation issue with a drive shower still may have this decrease in density, though some of the "other" factors are coming into play that prevent it.

Wow...I'm actually using this education.

Brad Holbrook.

Thanks Mike and Brad for the explanations. Don't know if that will be a problem for me as I haven't run the boat yet with the showers. Attached is a pic of the shower and another picture showing a similar shower installed (to show location mine is installed). The Latham unit barely protrudes below the cavitation plate surface (not like the shower shown in the pic).

I assume the pressure at that location eventually increases to start flowing water up the tube. Latham installation instructions stated to put it on the side of the upward rotation of the prop. Just curious, anyone out there running the Latham shower having problems with cavitation? I will find out myself pretty soon once the river drops.

I dont really know if it matters how far down or up the tube is past the cavatation plate,mine is adjustable and I tried with it up,down,half way up,still cavitates

If you don't have any luck with it they should let you return it.