proper prop ??? 85 hp johnson 1977

[sporty98]

I have a 13 1/4 x 17 prop is this right for a 1977 outboard v4 johnson 85 hp ? I was hoping to make sure and if also what would be a good pitch to have on it. I want to get another prop want to make sure I get right one.<br /><br /> thanks for your help,<br /><br /> sporty982000@yahoo.com

 

[JB]

Re: proper prop ??? 85 hp johnson 1977

Howdy Sporty. Proper prop selection is done for a boat/engine/usage package, not for an engine alone.<br /><br />To assess what you have now: Take your boat out with a light load. Run it to top speed and note the rpm. The rpm should reach near the top of your engine's operating range. I think your 85 tops at 5500rpm, but check it out. It may be 5000. Your 17" prop may be ideal.<br /><br />If your engine revs past the top of your operating range, you need a "longer" prop, say a 19". That should drop rpm by about 400 at wide open throttle (WOT).<br /><br />If your engine can't get up to top rpm, you can try a "shorter" prop, say a 15", which should result in a 400rpm increase.<br /><br />It is a good idea to keep a spare prop aboard.<br /><br />Let us know how you do.<br /><br />Good luck.<br />Red sky at night. . .<br />JB

 

[sporty98]

Re: proper prop ??? 85 hp johnson 1977

thanks for the info, my rpm is not getting to the 5500 with a 17, maybe I should go to a 15, I also need to thank you for the help with the decarbonizer info you gave last week. I ran some and man, I am getting alot getter gas milage, I have not rechecked the compression yet. I got a manual the other day for it.<br /> you would nto buy any chance know the part numbers for a impeller would you ? or a site that may have a listing of part numbers ?<br /><br />ryan