mated to stock 350's on a 28 foot boat,Are they really that bad?

No, they are well suited for small blocks. Just service them regularly.
Jim

I had twin alphas on a Foutain with 350's. Had the boat for 7 years and never ahd any problems with the drives or engines!

the guy also said they have upgraded gears to handle 500HP.Would they be considered SS drives?

SS drives are completely different. Don't know how it's possible ALPHAs could be up graded to handle 500 hp. They might take it for a while if you baby them. They did upgrade gears and bearings when the bb was installed in front of it back in '87. That just helped them tolerate a stock 330.
Jim

I had a Formula 242LS with twin Alphas/SBC - no problems in 7 years. Three of those years were with 385hp engines. They seem to do much better handling higher hp/torque loads in twin applications where they can share the load. An Alpha has a little better hydrodynamic efficiency than a Bravo, but is limited to its own applications.
I think everyone will agree on one thing- they don't care much for going airborne, especially if you're not good and quick on the sticks.

You don't want to holeshot or air out the prop with anything more than 300 HP. Big block torque will gobble hem up- even stock 330's. You also don't want to go from neutral into either engaged mode with the motor doing anything but idling.

Alphas have a bad-rap for no real reason. Worked great on my 26 Sutphen with twin 300hp SBCs. The only problem you'll likely face is resale.

My Father used to sponsor a Race boat back in the 80s that ran 600hp twins thru alphas and they had very few problems with the drives under those conditions. Dont beat them and you should be fine.

I had Alphas with small blocks on my 26 foot Wellcraft Nova II. Owned it for six years - no problems what so ever.