Prob and drive height suggestions for Donzi 25zx w 625hp
07-20-2014, 05:56 PM
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Prob and drive height suggestions for Donzi 25zx w 625hp
Got some time to run the new motor yesterday. Topped out at 70mph gps at 5100 rpm. This was a stock bravo1 24p with a 1.5 ratio. Old motor ran 60-62 with a stock 454 mag with a 21p rev 4 at 49000 rpm 1.5 ratio.
Motor seems strong...acceleration is very good up to 60,then it seems to hit a wall after 60. My prop is very deep, prop center line to bottom is at about 8". Calculations show about 8% prop slip with both motors. It is a pad bottom. I am thinking of trying a -2 lower next. The only other 25zx that I know of with a big motor was a guy that had 850 hp. He ran and extension box that raised 3" and ran a -2 shorty. He topped 100mph....104-105 I think.
I'm not looking to wring every last mph out of it, want good safe speed with decent efficiency ...but the math shows I should be closer to 80 mph. Any advice would be appreciated.
Motor seems strong...acceleration is very good up to 60,then it seems to hit a wall after 60. My prop is very deep, prop center line to bottom is at about 8". Calculations show about 8% prop slip with both motors. It is a pad bottom. I am thinking of trying a -2 lower next. The only other 25zx that I know of with a big motor was a guy that had 850 hp. He ran and extension box that raised 3" and ran a -2 shorty. He topped 100mph....104-105 I think.
I'm not looking to wring every last mph out of it, want good safe speed with decent efficiency ...but the math shows I should be closer to 80 mph. Any advice would be appreciated.
