Has anyone tried an IMCO standard length lower on the 37 Excess? I'm building a pair of spare drives for my boat, and was curious about the IMCO lowers. I was always under the impression that over 80 mph the design of the bravo lower starts becoming an issue. The IMCO certainly has better hydrodynamics, and I'm curious if in the 85-90 mph range the IMCO helped at all. Right now with bravo 4 blades I'm in the 19% prop slip, I'm curious if the IMCO would help that at all. I've used these lowers on other boats, and always had good luck, but they have also been straight bottom boats.

If the gearcase is submerged after 80 MPH anything with a longer gearcase that comes to a sharper point is going to help stop blowout.

That's what I was thinking as well, I have read about people having issues with blowout with Bravo lowers, even at much higher speeds. However, prop slip numbers do seem to be high at all rpm ranges unless you run 5 blades. I'm kind of on the fence switching to 5 blade props as I run in Lake Michigan 90% of the time, and I really don't feel like dealing with broken drives. I know that other people with other hulls have had slip numbers decrease with the lMCO lower, but I don't feel like making the switch if no one else has tried it.

I had -2 IMCO lowers on the SCARAB with slip at 14%
the Daytona has ridiculous slip at 40 but 4% at anything over 80
Prop shaft is 2 inches above the low point on the hull.

I was just looking at my data from my Formula when I was testing IMCO and Sportmaster lowers. Both drastically lowered the slip numbers. I wish I would have had the time to test everything individually but as you remember, there were also new exhausts, cams, carbs, intakes, and engines. So unfortunately I have no idea if there was a speed benefit for the drives, but there was absolutely a prop slip benefit. I've got a pair of XR lowers I was going to build, I think I may buy a pair of std case from IMCO, and see what the results are. My boat is supposed to run in the upper 80's as it is, so I would think the better case design would benefit the boat.