speed of a 79 201 marlin

[lime4x4]

Anyone know about what the max speed of a 1979 201 marlin with a 470 4 cylinder? Currently i get around 36 mph according to gps at a rpm of 4100. I think the motor should max out at around 4500. Currently there is a 21 pitch 3 blade alum prop on the boat

 

[moorehaven]

Max rpms should be about 4600 rpms . A 21P prop you might be a little over proped .I have a tried a 21p on my 201 and changed back to a 19p .