Evinrude 90hp V4 Prop selection issue

[MuskyHunterDave]

Hello. . . .
I have a 1992 Evinrude V4 90hp

WOT tops out at 5000, and I am doing aprox 32 MPH

The boat is an 18' 1/2 cuddy All Aluminum boat

The prop I just dinged is a
391198
13 3/4 X 15

I was curious if this looks liek the right prop, or shoudl I buy a different one when I replace the one I have, and If I should change size or pitch what do you suggest ??

I am a layment when it comes to props, so I was curious as to what the up or down change props would be and how it alters WOT and performance. I see a choice of 10" to 20" pitch prop selection, and that seems like a wide variation to choose from, what is the difference ??

Thanks again for the insight
MuskyHunterDave

Thanks
Dave

 

[Silvertip]

Re: Evinrude 90hp V4 Prop selection issue

The ideal prop lets the engine rev to its maximum recommended wide open throttle rpm. Whatever speed you get with that prop is what you get. As you've found, there are many props with varying degrees of pitch within the same diameter range. If you increase pitch, such as going from a 15P to a 17P in your case you would cause the engine RPM to drop by by 100-200 RPM per inch of pitch. That is not a good thing in your case because it means the engine is now lugging or working harder and hole shot would suffer severely. On the other hand, going to a 13P would help hole shot, allow cruising with heavier loads, but it would slow you down even though rpms would be higher. Remember, you decreased pitch so instead of moving 15 inches forward with each prop rev, you only move 13. There are other factors to consider and the most important is engine condition (tune) and its mounting height. If the antiventilation plate is below the bottom of the boat the engine needs to be raised (not tilted) but physically installed higher on the transom. The AV plate should be even with or an inch or two above the hull. Then and only then should you consider a prop change.