Thanks for the back-up on this, Firefox! I thought that my 18 1/2 "X" dimension (as we measure it) might be a bit tall for Connelly's application. When I did all that surgery to my hull I also cut in a 9" forward transom/keel notch so I have the benefit of a 9" setback from end of keel to front of lower unit. The 17 1/2" # you suggest sounds like the safest way to go for an "Outa-the-hole" boat. But remember...you can't make a TRS any shorter/higher once installed (there are no kits for this) yet you can probably find a prop that can hook you up even if you are plugged in a bit too high from the "get-go". Connelly, have we confused you yet?? --- Jer

The problem with compring a 27 excalibur is that it has a notched transom. On my boat the trnsom assembly is set as high as it can be. up against the rub rail. The centerline of the driveshaft is above the bottom of the boat. So my x would not help on this boat. It is sometimes interesting getting on plane with a heavy load. But we don't use it to ski behind so no big deal.

Actually there are 2" spacers that can be placed between the upper and lower on a TRS. -- I pulled them out of my drives. Just an FYI

Jpclear, Thanks for checking your Martini for me and also thanks to Firefox for the additional thoughts. I had to think about it for a while as it's a different way of looking at it but I think I get what you are saying. Just to confirm:
1) Put a straightedge under the keel to extend the keel line and then measure up the X dimension (17 1/2"), at 90 degrees to the straightedge and mark a line on transom. (as opposed to measuring against the transom from the keel )
2) Set the transom plate so that the CL of the crankshaft / input shaft passes through the transom at the height indicated by the mark.

Am I confused or have I got it?

Connelly21