prop selection

[fordsohc46]

what prop size should i have on an 1977 85hp johnny. the motor is on a 18' bass boat similar to a ranger 370v from that year. also how do you measure pitch. im wanting to order a new prop and would like to get more speed and accleration if possible. thanks in advance.

 

[Silvertip]

Re: prop selection

Did you look at the prop you have now for some numbers? Diameter and Pitch are normally stamped on the barrel of the prop or cast into the hub of the prop. You might have to remove the nut to se the number. You can measure the diameter. Measure from the tip of one blade to the center of the shaft and multiply that number by 2. You should find either a part number or numbers that resemble this: 13-3/4 x 19 (13-3/4 inches in diameter, 19 inches of pitch.) Since we have no idea what prop you have now, and you have not told us how fast your boat goes now, and what the maximum wide open throttle rpm is, we can't possibly provide any realistic responses. While you ponder that -- take the time to read this:

http://forums.iboats.com/showthread.php?t=158083

When you have some data we can work with, come on back.

 

[fordsohc46]

Re: prop selection

i will get the numbers off the prop. i know the max speed with two people and an ice chest and fishing gear is 42 mph. i have one problem though, my tach doesn't work so i don't know the rpm at wot. do i have to know that to select a different prop? if i can't get the tach working should i just replace the prop with the same as original?