That's really cool, That engine/drive package is pretty rare, an original Alpha SS is tough to come by. Very cool package. The SS is a little over 2 inches shorter than a stock Alpha, and the couple I/O streams I've seen had the x dimension set up pretty high. I wouldn't change a thing.

^exactly. I think you could probably bolt on a normal gearcase to that outdrive and not hurt anything. and you could find parts. Ive worked on a few of those outdrives doing gimbal bearings and water pumps, and they look exactly the same with the exception of that gearcase.. which I would not expect to see on an I/o that is buried to the cav plate and a stock 270hp mercruiser chevy. I would look into that. might not need that fancy gearcase on that boat

I think what Aaron is getting at is that the outdrive is fixed to the transom, and as with most outdrive installs, is low enough below the hull to not necessitate a low water pickup. By trimming up (and producing a rooster tail) what you're doing is essentially lifting the bow by driving the back of the boat further down into the water. Ideally what you want is neutral trim and low rooster tail. That way the prop is driving the boat forward efficiently, not wasting energy carrying the bow or being too deep and forcing the back few feet of the hull into the water. Wish I could draw a picture to explain it better. Anyways, with an inboard/outdrive setup, the outdrive typically isn't high enough to run as efficiently as an outboard. It's well under the planing surface of the hull (the pad on a 'stream) and therefore creates efficiency issues, affecting speed and handling characteristics. If the outdrive was adjustable in height (which I doubt, but is the core of Aaron's question) you could raise your prop shaft height and make the setup more efficient, enabling higher speeds. As you go higher with your drive, you need to worry about where your motor is getting it's cooling water from, hence the "low water pickup", which is an aftermarket (usually) modification to get cooling water from a lower point within the gear case. Hope this helps your understanding a bit more!!

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Hey Aaron,
I honestly don't know the answers to your questions. I'm still very new to the hydrostream fan base. What I do know is that being trimmed up doesn't drive the hull down. In the pictures I took the trim is on the trailer setting, so that may be why it looks that way to you. When I'm driving it the higher I trim it the more it feels like the boat is about to fly on me until eventually the prop will break the surface of the water. One other bit of information I know is that this out drive is one that was used by mercury racing on their boats in the 90's. It's some upgraded version of the alpha. I only know this because about 6 years ago, when my dad owned it, one of the driveshafts in the drive snapped and we couldn't find any replacement because they were never mass produced. We had to have one custom made by some guy in Pennsylvania. From what I've gathered this boat is kind of an anomaly because there weren't many made and the information on them is incredibly scarce. There are tons of other guys in here who may have much more information on your questions, at least I hope so because I'm curious as well. Thanks for the reply!

I know this is an older post already, but im noticing the low water pickup on the gearcase. What is the point on that outdrive? Did hydrostream install their outdrives high enough to need that? Is it possible at all to raise the propshaft height in that boat? Seems like it would dig the hull into the water if you trimmed that up at speed.

By the way you described it, it does sound similar. I know wide open there is only about 6 inches of the hull in the water. It only does that trimmed up though. When you trailer it up past full up it starts getting pretty unstable. It makes it throw up a heck of a rooster tail though. I'll try to get a video of it running next year. It's too cold for my preference to take it out any more this year. I do have a picture of it running somewhere. I'll try to get my hands on it. I think it may be mixed in with my mom's old pictures at her house.

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The pad is the flat surface at the bottom of the hull. It's the running surface of these Hydrostreams. Being a v-pad hull, instead of coming to a point at the bottom, as a typical v hull would, there's a flat bottom, called a pad, that runs on the water's surface. Running on the pad is what I mean by flying it. With an outboard model, you can run these hulls on the very rear of the pad, with only a paper towel sized section of the hull touching the water. I'm wondering if the io model is set up to run similarly. By the pics you posted, it looks like the prop shaft is still well below the pad. That's why I was wondering what your trim angle was at top speeds. I guess ultimately I would like to see a video of this thing running balls out. You don't see many of them, and I think you're the only one I've seen contributing to an open forum! Welcome to the site btw, hope you stick around, I really like this boat!!

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Sorry, but I'm still learning boater lingo. I'm very familiar with car engine and components, but up until this spring I've never worked on a boat. Prop shaft in relation to the pad? What is the pad? Also what does fly it mean? Getting it on plane? Also it's 320 hp. It's the same motor corvettes ran in 90, even has corvette flags on the intake. Tomorrow I'll post motor pics if you guys would like.

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Not to be difficult, but where is the prop shaft in relation to the pad? How much hp is the TPI running? How much trim to fly it? I'm very interested on how these run compared to an outboard model. 82mph is very respectable!

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Here are some more pictures of the back, per request.

[size=75][b][i][ Post made via Android ][/i][/b][/size] [img]http://www.hydrostreamforums.com/images/mobile/Android.png[/img]