I have a 30 ' scarab that i'am redoing, blower motors ,hydraulic steering, total re-rig .I desided to build my own extension boxes i've read alot of the posts on extension boxes and talked to someone who built his own.I want to find out the the best prop centerline to hull running surface dimension and work from there ,the drives are TRS which i will install nose cones due to the 12" set back, the reduced x dimension and less trimming of the drive.The boat should run mid 80's in original drive form less boxes with 575-600hp.Would moving the drive up 2" be enough or more needed?

Without knowing just where you are starting it is not possible to tell you how far and in what direction to go. So lets talk distance from prop shaft C/L to running surface, extended. Depending on the use you intend and type of prop you expect to end up with for that use, that distance could be anywhere from 2-1/2 to 5-1/4 inches, and that is a BIG variable. My old single TRS drive came from the factory totally BURIED. I raised everything 2-1/2 inches and my prop shaft is still 5-3/4 below running surface. If I were doing this all again I would NOT run deeper than 5.0 with a TRS and nosecone. And there are props out there that will really work for all-round at a 3.0 inch depth. Talk to Julie or Matt at Throttle-Up before you do the final cut, fill, and glass. --- Jer

I put Hydromotive nosecones on TRS outdrives on an old Scarab 400. They must have smoothed the waterflow to the prop a lot. Rpm's dropped by 200 while speed stayed the same. If I were going to raise the drive a lot, I'd put on nosecones to insure continued clean water to the prop.

Just had Konrad conversion on 38kv Scarab with buddy's boat. It turns out that the Scarab already had a high X dimension and we needed spacers. The Konrad's came 2" shorter. we tried all kinds of props, spacers etc. and after hauling the boat out 3 times, switching drive rotation putting in bigger spacers, eventually got it right.