what are normal numbers for prop slip on a setup like mine? 1986 formula f3ls, zz4 crate motor, 21p mirage. According to my calculations it looks like about 7% which seems crazy to me. I am used to light outboards where my 29p @ 9.5% slip is pretty good, so it just doesnt seem right that a 4k lb boat can have LESS slip!?!?!

we need your numbers.... pitch,rpm,speed,gear ratio

21", 45-4600, 57-58mph, gear ration I am not sure of. its an alpha one, seem to have read somewhere its either 1.47 or 1.50

Are your speeds GPS and is your tach accurate (86 would be an old tach to be using without vertification)?

Julie

no verification on the tach, it may or may not be original, i know its not new lol speeds are gps

i know how to calculate slip btw. i just want to know what a normal accepted range is. i have a small out board boat that is pretty well setup, so i know all about prop slip in that setting

7% slip in an older single engine straight hull is highly unlikely. I think you need to verify the tach and gear ratio in the drive.