350 magnum build suggestions.

[Firechickenws6]

I am looking at a clean 1986 Baja 220 Sport with a Mercruiser 350 Magnum and what looks like an Alpha outdrive for a project that I can pick up for a deal. Planning on pulling the engine out and doing a full tear down to see exactly what I have but I would like to re-use the 350 block. I am shooting for the 80-90 mph range. triple digits would be awesome too. I would really like to at least outrun my dads Bullet 21XD that will run in the low 80's. From what I understand the outdrive on it right now is only good to about 60 and was told I would need a bravo for those speeds.

I have built several 3rd 4th gen LS based engines and also work as a technician so taking anything apart and rebuilding it is nothing but I have never messed with hot-rodding a small block in a boat.

My questions are:
Why do I need to do to the outdrive to beef it up to handle what I want to throw at it?
I have been told that the Mercruiser 350 is nothing but a Chevy 350. True or false?
I like smaller displacement higher RPM engines, will this work for a boat if I set up the prop and final drive gear right?

Thank you for any help.

[b0atguy]

With an Alpha, its not a speed limiting factor, its a HP factor. Alphas are capable of holding approx 300hp, before they fly apart. Bravo's are good to about 1000 hp!
Mercruiser tried putting Big blocks on alphas in the mid 80's...........didnt work out too good. Bravos were born.
TRS will hold the power also, but are getting scarce. Bravos are plentiful. To change over to a bravo, you will need to change out th entire transom assy.
The most HP Mercruiser put through an alpha drive (succesfully)was the 320EFI, small block GM........but that was an alpha SS.........VERY RARE.
If you can keep the HP in the low 300's and dont put out the torque of a BB, you should be O.K. with an alpha set-up.
Just keep a spare drive on hand!
b0atguy

[Euroski]

Back a few years ago there was a member building a 100mph stingray with a beefed up alpha. Maybe one of the older members can find the thread he started. Orignally he was called tripple digits but had a name change.

[rev.ronnie]

The factory heads on that engine are the worst small block Chevy heads that ever saw the light of day.

You're gonna need to figure out where you are going to want that engine to make power and what cubic inch it ends up (hopefully a 383). The Dart Iron Eagle Platinum heads are the most common heads I use in small block marine engines. Pump gas, hyd. roller, 5200rpm, 500 HP 383 engines are a popular combination. You are going to need the exhaust system, lower and upper to support it though.

If you seriously want to get that rig into the 80-90 mph range, you're gonna need a Pro-Charger and the parts to support the 750 HP you are gonna need to make. I've built some low deck 369" fords that make 900+ HP with a pro charger, and that was only half the battle on a boat...