Prop for 1957 18 horse Johnson

[55Crestliner]

What exactly will a prop do if it is chipped up on the leading edges? Will RPM be lower than if it was perfect? I think I know that the speed will increase, but what about rpm?<br /><br />I am seeing 4700rpm (supposed to be 4500 for this motor) with a 9-1/4 x 11 (ragged edges). A 9-1/4 x 13 cupped was turning 4000rpm. This is a pretty light load, I will occasionally be adding another 160#'s to this.<br /><br />My real question is this - should I buy a brand new 9-1/4 x 11, or would a 9-1/4 x 12 be best?

 

[JB]

Re: Prop for 1957 18 horse Johnson

Stay with the 11" pitch, Crestliner.<br /><br />You can buy a new one and keep the present one for a backup.<br /><br />You can have the present one reworked. Probably cheaper than a new one.<br /><br />You can get a cheap plastic one (Comprop) for a backup.<br /><br />Good luck. <br /><br />Lots of options.

 

[walleyehed]

Re: Prop for 1957 18 horse Johnson

JB beat me to it.......stay with the 11.

 

[55Crestliner]

Re: Prop for 1957 18 horse Johnson

12 would be slower to accelerate - is that what you guys are thinking? Put the rpm's too low?

 

[steelespike]

Re: Prop for 1957 18 horse Johnson

Stick with the 11 get it fixed up.It will give you more jump and handle the 160 additional lbs easier.<br /> Im pretty sure you can run a little over the 4,500 rpm rating and if it makes you nervous just back off a little.Dont forget to adjust the<br />virtical height for the best performance without ventilation.Get the prop fixed and you may find it has a little better bite.Dont forget the motor trim as well.Try to distribute weight so you dont have to use motor angle to trim the boat.<br />I have a 56 Crestliner 17' utility with a 65 Merc 50. Im the 2nd owner.I used to ride in it when it was new.Its still pretty nice.

 

[55Crestliner]

Re: Prop for 1957 18 horse Johnson

Thanks for the thoughts all. Sounds like the 11 is the one. I was hoping for a touch more speed, (not sure why, 25 is plenty in this boat )but I don't want it to lug.