I don't run a drive shower. No one has proven to me with a temperature gauge that they significantly lower drive oil temperature. Also, the oil is intended to get hot, that does not mean it stops working. Have you felt your engine oil filter after a hard run lately?

thirdchildhood, I dont think its a huge temperature drop with the shower but it was enough on the couple of boats I had in the past to stop the oil from getting roached, the case was much cooler to the touch with the Simrek on, and I gained 11 mph on a 95 Baja 272. Just kidding on the last one.

The white glaze that forms on a drive after awhile is deposits from water boiling off the drive. A decent drive shower will at least lower the drive casing temp to the point the water doesn't boil and leave the white deposits. I've had the same experience as VoodooRob, always seemed to keep my oil in better shape, meaning not turning roasted black. Those two points were reason enough for me to spend a few bucks on drive showers.

Is this a mercruiser issue or do the volvo's suffer from the same? I have not seen a shower on a VP.

http://www.driveshowers.com/reviews.htm
Scroll down the page to read the articles vs clicking the links.

I've had a few Simreks and not bad for the money. AADS did a full rebuild on my drives prior to my purchased. I noticed one shower was developing a crack. Simrek said it was a drive related issue. Called AADS and they recommended Eddie Marine. They stand behind their product so that was enough for me. Ordered two EMs and haven't looked back.

I've always wondered why there isnt an external oil cooler circulating to the drives from the factory. Oh wait, found my receipts for 2 new XR drives, dummies like me will keep buying them.

Yes a Merc issue. Volvo's run oil pumps that circulate the oil from the lower to the upper and that will cool the drive while on plane.

Since 2000 Formula has been adding the Simrek showers to the Merc drives before the boats leave the factory.
I am adding the Simrek Halo to my Bravo's this season before launching. Last season I got one drive hot enough to puke the oil out of the reservoir after running 52 mph for about one hour; not cool. Pun intended, lol.

If they are fixing a problem with the oil burning up, yes, oil can get too hot, then I guess they are a benefit. I change my drive oil after every boating season and it always still looks fresh. I've never run a drive shower. I know that I'm in the minority.