Raising the X Dimension on an Alpha One?
 

Hey guys. I just finished installing a new transom in my 1969 Sea Ray SRX Pachanga. It's got a stock 1985 Mercruiser 5.7 and Alpha One setup. I'm getting ready to cut the keyhole in the new transom, and I've been doing a lot of X-dimension research, but I'm still undecided on what I'm going to do. My questions is this: what are your opinions on raising the X-dimension for more speed on this application? I'd like as much speed as I can get without needing special parts, (other than maybe a prop.) Basically, it's only because I'm starting with a new transom anyway. How much can I get away with raising the X dimension, and what would I sacrifice in doing so? Thanks in advance.

You are going to want your prop shaft about 4 1/2 inches below the bottom. The problem you have is with the drive itself. They can last if driven gingerly but that does not sound like it is what you are looking for. If you start getting air, you will grenade the drive. Have you considered a Bravo? Plenty of options for making a bravo last.

A bravo would be awesome, but not really in the budget right now. Maybe down the road. Really I'm just wondering how to get the most out of the location of the keyhole I'm about to cut, if that makes sense. How did you come up with 4 1/2 inches?

Rigged boats in a former life. Your bottom is probably close to the shape of my old Minx. It was 7 from the factory, after going to the recommended 4.5, it was a whole new boat. Most manufactures will set them up deep knowing the average boater will load up with people and gear.

Ok, sweet! How much more did you get out of it?

If srq is watching, I got your PM and responded, but it says your inbox is full.

Picked up 2-3 mph. Not a big deal but the handling was a world of difference. Had to spend some coin on props to dial it in.

Keep X in the stock location and find an Alpha SS drive.
Engine stays lower in the boat and drive height will end up at 4" below bottom.
Don't believe all the hype about blowing up the drive if you fly it, build it right, throttle it properly and it will last.

bravo and alpha are same length, so you wouldn't hafta redo the hole when the right bravo donor boat shows up...but measure all the way to the top. start at new prop centerline, add drive height. now see where crank centerline is, and mock up engine in boat at that location. see how it fits in the boat. another reason builders put them deep is how engine fits under seat or sun pad...