1989 johson 120hp prop size

[roypretty]

hey everyone. I have a 16 ft sunray express with a 1989 120hp johnson . It currently has a 13x19 stainles steel prop. At wot iam getting 6000rpm but should be 5500. I would like to put a 14.5x19 or a 13x21 prop aluminum but don't know which one to use. My goal is too reduce my rpm too 5500 and save gas, which would be the better prop.Maybe someone has this similar set up. Thanks

 

[Dhadley]

Re: 1989 johson 120hp prop size

We'll assume you have a 20" motor which has the 4 1/4" gearcase with a 13 spline propshaft. That will use the V4 type props in the 12 3/4" to 13 1/2" diameter range. There's nothing wrong with propping that particular motor to 6000. 5500 would be border line lugging, I wouldn't target anything less than 5800.

A good design 20 or 21" pitch prop should serve you well. Something like a 13.5 x 20 or 22 Raker would be an interesting choice. Too bad Turbo doesn't make the Lightning Jr anymore. The 13 1/4" small Turbo or Stiletto should do a good job too.

 

[roypretty]

Re: 1989 johson 120hp prop size

thanks alot.didn't know 13.5 diameter was max.

 

[Dhadley]

Re: 1989 johson 120hp prop size

You might get a 13 3/4" prop on but most 13 3/4" props are made to go on a V6 style case. Does your propshaft have 13 splines or 15?

 

[roypretty]

Re: 1989 johson 120hp prop size

hi.yeah it has 13 splines. I just found a prop 13.25x21 alum for 157 plus tax. omc with the hub inside.cheapest i could find