Welcome aboard
I think you mean the engines are 7.4 not 4.7 or could have ment 5.7.
Mercruiser designed the BII for large heavy boats before they could sell the BIII as Volvo had a patent on the dual prop. The BI is for high performance boats as the Alpha is rated to 300 HP max.
With that said older big , per Bravo boats came with Alphas which swing the same size prop as the BI so you could do it but will have to experiment to find the best props. Quicksilvers prop calculator may help. However you will sarfice performance, mainly acceleration and planing time.
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1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2
Mike
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