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donzi fonzi
12-20-2010, 05:20 AM
i have a 1974 16ft with a 302 ford and its running a volvo 270 leg LH rot with a 15x21 prop does anyone know about changing it to a largder pich to get more top end speed or can steer me in the right directon

thanks Daniel

Sweet little 16
12-20-2010, 08:54 AM
It would help if you posted your current numbers with that prop.
rpm,speed by gps,drive gear ratio.

plus pics are always good too

mrfixxall
12-20-2010, 11:18 AM
smaller diameter and bigger pitch will make you go faster but to you have the extra power to turn a bigger prop?

donzi fonzi
12-20-2010, 03:22 PM
its about 55mph at 5000 rpm ill check wiyh gps and up load pic

Sweet little 16
12-21-2010, 08:32 AM
that's about the right ballpark 11.5% slip on a 1.6 drive

not sure just propping is going to be your answer. it might get you a mph or 2.
running your numbers a 15X22 would be the same speed at 4800 rpm.


maybe as mentioned dropping an inch in dia. would negate the 200 or so rpm you will loose going up an inch in pitch.

if you could turn a 14X22 to 5000 rpm and keep your 11.5% slip you are up to 57 mph.


if your target is 60+ on an old skisporter

the path is usually:
a warmed up small block 350 + HP
nose cone
trim
and a 25 or bigger pitch prop