Re: Going from 260 to 300hp
Is there a general rule of thumb on a prop change due to an engine swap and gaining 40hp?
I think the rule is you won't really know until you run her. My issue is with how both examples horsepower is calculated and actually what the horsepower is. Unless you took them both out of the boat and dynoed them, then you really don't know if it's 15 or 75 hp difference, and at what RPM. Soooo, I think the best answer is No.
Be aware your current 260 would be a 230 if it was rated as I/Os are today (prop). And you have to know whether the Rapido would really be around 265 or 270 if rated at the prop, or is it a true I/O 300 rating which I doubt. A little related side note, today a 260 bhp 5.0 MPI I/O has 30ish more ponies than the old "260s" . . .
My guess is that a full 2 inches is a big jump to hope for, and then of course blade count etc. comes into play. I'd try the 19, break in as they recommend, and then give it all she's got. If she's pulling hard as you reach the high end of WOT range (Rapido's call) then you have to judge from that. Good luck, like always, you really have to experiment . . .
