Mercruiser 5.7 (not stock) with Alpha One outdrive - Prop Info

[Nautidawg20]

I have a 1994 Century 230 Arrow with a modified 350 (bored .040 over, .528 comp cam and Rochester 4 bbl carb) paired with a Alpha One Gen 2 outdrive. The previous owner was running a 13"x19P prop which resulted in 5200 rpm at WOT with just me on board and a full tank of fuel. The boat ran approx. 62 mph in this configuration however, I was more concerned with the rpms. I borrowed a 14.25"x21P prop and the results were 4000 rpm at WOT and a top speed of 55 mph. This was not what I assumed would happen. Looking for anyones input as to which prop size would be best for this setup. I would love to maintain (or increase) the previous top end, while reducing rpms. Thanks in advance!

 

[emilsr]

Re: Mercruiser 5.7 (not stock) with Alpha One outdrive - Prop Info

It's hard to determine what rpm is "good" for a non-standard engine unless you built it. 5200 might be okay. What did the engine builder say to run it at?

You got what you should have expected from the prop change; bigger diameter, more pitch, rpms drop.

What (exactly) is this 13 x 19 prop?