19 pitch too low 21 pitch too high 73 evinrude

[hootey135]

I have a 73 evinrude starflight 125 on an 18' trihull (heavy boat). It has an omc 13x19 with no cup. The ring on the back of the prop is missing. This prop will allow the motor to rev to over 6000 rpm. I tried a buddies 13x21 pitch with no cup and it had the ring on it. It wouldnt allow the motor to go over 4900 rpm. Does the ring make that much of a difference? I am told there should only be a 200 to 300 rpm difference between these two props. Please help.

 

[Boatist]

Re: 19 pitch too low 21 pitch too high 73 evinrude

Hootey<br />I would expect about 200 rpm change per inch so for a 2 inch change about 400 RPM difference.<br />Many props do not need a ring while other will cavitate with out it. If it is supposed to have a ring I would not use it until I got it fixed. Both my Stainless Steel props do not have rings. If one prop is Stainless and the other Aluminum that also makes a difference. What is your recommended WOT RPMs??

 

[hootey135]

Re: 19 pitch too low 21 pitch too high 73 evinrude

The recomended range is 4800-5500. Could the 13x19 be messed up? The boat does not cavitate with it. Neither prop is stainless. Thanks 4 the reply.

 

[Hooty]

Re: 19 pitch too low 21 pitch too high 73 evinrude

Either one of them could be screwed up. Take'um to your local prop shop and have 'um checked. <br /><br />c/6<br /><br />Hooty