1988 V20 steplift/305 chevy, mercruiser drive.

[THEFERMANATOR]

It depends on which drive you have. The early ALPHA units are rated to 300HP at the flywheel, and teh later ALPHA's are rated to 300HP at the propshaft IIRC. The pre-ALPHA drives are a bit weaker by design I believe though. As for high RPM's, they don't take well to that fro mwhat I understand. Theres a guy at screamandfly that mods the ALPHA drives to 400HP or say and 6500 RPM's, but this is for light applications, a V-20 is not considered a light application for an ALPHA drive. 5,000-5,500 is fine on them, and if you plan on going over 260Hp at the flywheel I suggest running the exhaust through the transom and install a drive shower along with running synthetic lube in teh drive as heat is teh enemy with the I/O's. And torque is teh killer for an ALPHA as the gears in them just are not meant to take the abuse(Ibelieve teh ALPHA's use the same basic design as the 3.0L MERCURY 2 stroke outboard lower unit).

[spareparts]

ferm has it right on the numbers. If you want a reliable package, the 383 might be a bit too much for every day use. Merc sells their own 383(320 hp) and usually puts it in front of a bravo. For what you are doing with a V, a good strong 5.7 would be enough.

[step up here]

x 2 times, they are right on the money. i currently own that combo. 1986 vintage!

[brisboats]

Mercruiser put the alpha one behind the 454 for a time and it was a disaster. The torque of the big block would wipe the upper gearset in hard use. The alpha is good for about 300hp and you cannot run it like an offshore powerboat when you have a hot smallblock even with a drive shower and extra reservoir for the fluid. Car hot rod modifications do not really work all the time for boats, your rpm range is to high.

Brian

[THEFERMANATOR]

Originally Posted by brisboats

Mercruiser put the alpha one behind the 454 for a time and it was a disaster. The torque of the big block would wipe the upper gearset in hard use. The alpha is good for about 300hp and you cannot run it like an offshore powerboat when you have a hot smallblock even with a drive shower and extra reservoir for the fluid. Car hot rod modifications do not really work all the time for boats, your rpm range is to high.

Brian

And that 454 ALPHA had a custom set of 1.36:1 geras in it built just for the extra torque and it BOMBED!

[spareparts]

The 1.5 HD gears were actually stronger, the 1.32 had too small of a driven gear. I had a customer that ran a 720hp Troy Dennis blower motor in front of an Alpha SS. he changed the lube every time out, never drag started it, rana duel shower and usally only ran other boats from 65 on. We had the 1.5 HD but ran out of prop options, ended up with 1.32 and a 27 Mirage(double cupped and labbed), biggest prop we could find with a rubber hub(pre plastic hub days), boat radared out at 101. I still put a fresh set of upper gears in every spring

[UBHSTRY]

Ok, could you help me with the location of what would identify exactly which outdrive unit I am working with?