‘92 Formula 357 Winter Project
 

Hey everyone!!

First time posting on here. Been reading these forums for years and they’re always helpful.

Going to re-power my baby over the winter. I currently have a pair of 502BBC with Bravos. Top Speed is 72mph.

My biggest goal it to equip the boat with power big enough so I can cruise in the high 70s and maybe Top Speed in 87-92mph area!

Is this possible? How??

I know it’s a heavy boat without a step in the hull but there’s gotta be a way!

Anything you guys got for me is much appreciated! Would love the conversation.

Running in the 70s with a 357 is an accomplishment in itself. They’ve got to be making 550-600hp a side to run those numbers. Cruising in the 70s with speeds in the upper 80’s/low 90’s is going to be a huge undertaking.

Big cubic inches. Superchargers. Drives (and if TRS… transmissions) that can handle the power and weight. Big boat!

Will be interesting to see where this goes!

We love pictures!

Welcome to OSO, get your post count up to ten so you can post pics. It would be interesting too see how much HP it takes to get to 90.

I had a '93 357 with N/A 540's making 600 hp each running through Bravo One drives. I used stock 28 " pitch Bravo One props and ran 72 mph at 5000 rpm.

Big boat!!

FWIW, make your big power engines reliable and refrain from making so much power that you’ll be replacing drives regularly. Using the boat is so much more enjoyable than constantly wrenching on it.

You'll need roughly 1,000hp each to hit 90 mph........no way in hell those Bravo drives last more than a couple hours behind that. Surface drives would survive the HP and also help you achieve faster speeds.

Now you've spent a stupid amount of money to make a slow boat still slow by today's standards.

The best way to "cruise" around at 70 is to run the boat WOT knowing you're going to be rebuilding the existing motors much sooner.

Would it be more sensible to have a goal of doing 80ish for this project? If I go with a pair of 540s that make somewhere between 650-700hp do we think that the Bravo 1 drives that I have now can handle that? What causes a drive to break? Is it too much HP and Torque or is it more of someone just spinning the drives when they get airborne?

Without a stepped hull it takes large increases in power for small gains in speed. I've had 3 Formula SR-1's (272,311,357) and while they are great boats in the rough they are not designed for top end speed.A 38 Fountain, for example will run 85 mph with HP500's, which is about 20 mph faster than a 357 will do with the same power. Keep the Formula reliable and enjoy it for what it's made for.

A standard Bravo will not like that kind of power trying to push a 357.

ICEDPPL with the Cig Flat Deck just crossed 100mph. Took him 12 years in progress to get there.

https://www.offshoreonly.com/forums/...ispreloading=1

357s are one of my favorite boats.

80 would be a more realistic goal, but you would still need a lot of power to get there...and reliable drives.
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What power are your 502s putting out?

Getting the drives up a bit in rpm vs lugging them, will let them live longer. Like a transmission, rated in tq vs hp.

It would also make it easier to get power out of the 502s or whatever you decide to re-power.

The Blower Shop is the best around for blowers that I've seen. A relatively mild valvetrain with good heads and 6/71 will get you most of the way to the lower end of your goals. But you'll need forged internals for any reliability.

There's a gentleman in Michigan with a 357 running prochargers on 572's, 900 HP a side if im not mistaken, with Konrad drives. He's running right around 90 GPS. That boat is a serious runner. Reaching 90mph with the old flat bottom boats isn't cheap.

Stert stripping some of the weight out of it.