I had the newer model, a 1989 w/SBC and I think they optioned BBC/330hp starting 1990. Not sure if hull bottoms were the same, but mine had a pad.

Scarab 1 engine options
 

Has anyone put a high revving 302 chevy small block in a 21' boat

Drive becomes a problem I think. Max designed rev is around 5-5200 for Alpha. I've turned them 55-5600 without issue (blower was the issue...different story)

Not sure how relevant this is...but just throwing it out there...I have a 21' Baja with a big block in it, it does just fine without tabs. It's got a 17 degree deadrise...not sure how that compares to your Scarab? Weight is around 3,500 pounds.

The big block wasn’t offered before merc had a good option for a drive without a transmission. Bravo drive wasn’t available until ‘88.

plenty of later small block options that don’t include the old school thought of a dz302

what kind of speed does it run, & u pull skiers also?

Engine options scarab 1
 

Ok i hope im not entering this twice, but when i submitted it, it disappeared, may have deleted, i am new here and hope this isnt a dumb question but just like tricking out a motor & making it twice as good, can the alpha 1 outdrive be "tuned up" or made better like maybe spin balance shafts, gears, upgrade to harder metals at weak points. And curious what is a ballpark figure to upgrade to the bravo 1?

I don't know of any modifications to improve the strength of the Alpha, it's just plain small. I have sold used Bravos with transom assy in good condition for $3,500.00. Good used parts are out there, you just need to be patient.

Valid question, but would be a waste unless they had one and just had to do it. Cubic inches are your friend. 350/383/406 much better small block choices. I have not been in a ScarabI with big block, so can’t answer how they handle.

Mid-to-high 60s with a 21" labbed Mirage. Great for watersports, I used to ski and kneeboard a LOT before I got old, lol!