the rule of thumb is 2% per 1000ft, is what you lose on hp.
if you build your engine accordingly to your alt. to get the 330hp the alpha should take it, if your careful out of the hole.
larry

Ok, so the '87 mag is really 330hp? I was planning on upgrading to a roller motor w/ roughly the same cam specs.
From what I can tell the 1996 & newer 7.4s have about 50 more Ft lbs than the older non roller version.

I also think I can upgrade to the gen 2 alpha for about the same it would cost to change the gears in the gen 1 alpha.

Holeinthewater / I haven't checked the gearing yet but your saying the stock '87 gen 1 alpha was probably 1.32?

I've always heard we loss about 20% power @ the 5-6k' I boat @.

I've also heard the alpha hold up longer in lighter boats. Is 4200lbs still considered light?

In 1987 for one year only Merc called the 330 hp 454 a magnum and put the Alpha drive behind it. I had a 27' Mach 1 back then and I beat on it pretty bad without problems, but I heard that many were blown up and that's the reason they only did it for one year. Why make problems if you know you are at the limit?

There are plenty of idiots that have blown up stock Bravos as well
with stock 454s,slamming into gear,dry start holeshots,flying waves etc. On the other hand there are plenty of Alphas behind 454s that have lasted many a year, most important thing is nut holding the wheel.
My Alpha is 25 years old and going strong,its had a 260/350 a 300/350 a 310/454 and now a 502 in front of it..
but I respect the fact its 25 years old and treat it as such.doesnt mean I dont run flat out every once in a while it just means I use my brains on getting there.

Good news! The drive has already been upgraded w/ HD 1.65 gears.

I found a 97 truck 454 vortec I was considering installing. Any idea what the truck cam specs vs the 330hp marine cam specs are?

Doesnt sound right.
V8 Alphas came with 1.5 gears and some 454 ones
used 1.32 gears ..

I turned the shaft a little over 1.5 times for the prop to only turn once. Plus the guy I got the boat from said they have been upgraded & replaced.

Any idea on the cam specs?

Definetly doesn't sound right. You'll need a lot of pitch if you run those gears with a big block.

I'm hoping to run a Rev 4 21P I have left over. Just not sure this mild motor will be able to turn it.