Prop for Evinrude 90 Special

[JSMoore]

How about a replacement prop recommendation? Please recommend both aluminum and SS models.
Thanks!
JSMoore

1) Performance issue you are trying to correct.
Lower RPM slightly and get slightly higher top speed.

2) Current prop manufacturer, model, aluminum or stainless as a minimum.
Unknown manufacturer, aluminum, 3 blade with almost no cup.
Note: The prop blades look real thick. It also looks like it may have been damaged and repaired at some point.

3) Current prop diameter and pitch (required).
14 x 17

4) Wide open throttle RPM and speed with an average load (very helpful)
5600 - 5800 RPM - 29 to 30 knots (on GPS) - 38 gal fuel, 2 people, average boat/fishing gear.

5) Engine/drive make, model, year, and HP
1997 Evinrude 90 SPL

6) Boat make model, year, length and weight
1997 Sunbird Neptune 180 CC, 18 ft. 2009 lb (dry) - Center Console In-shore bay boat.

 

[steelespike]

Re: Prop for Evinrude 90 Special

Your numbers don't add up.I think your tach is not accurate ,reading high.
Your slip is at about 26%, very high, Most likely the tach. You may be able to verify with a shop tach.
Sometimes there is a switch on the back if you note its position and operate it a few times to clean the contacts
it will help.

 

[JSMoore]

Re: Prop for Evinrude 90 Special

Your numbers don't add up.I think your tach is not accurate ,reading high.
Your slip is at about 26%, very high, Most likely the tach. You may be able to verify with a shop tach.
Sometimes there is a switch on the back if you note its position and operate it a few times to clean the contacts
it will help.

I suspected the tach in the beginning and checked it with a Sun SuperTach. On the water @ WOT, they're very close to the same reading. (Although, I certainly will cycle the switch on the back of the tach a few times to see if anything changes.)

I checked engine mounting height because I thought I might be right on the edge of cavitating. But, engine height looks good as well. The cavitation plate is almost perfectly in line with the bottom of the hull.

Just to add another set of numbers to this. A 4,500 RPM cruise setting gets me about 23 to 25 knots on the GPS, (depending on current, wind, etc.).

As I mentioned in my original post, the prop that's on there looks like it's been damaged and repaired. Don't get me wrong. It's not all dinged up. In fact, it looks very good. But, the leading edges of the blades are VERY thick and rounded. It kind of looks like the leading edges might have been cut back and rounded to repair rock strikes. I also see little, if any, cupping on the prop. Could that account for the slippage?
Thanks!
JSMoore

 

[steelespike]

Re: Prop for Evinrude 90 Special

from your description it does sound like a prop replacement is in order.
The Solas props have a good reputation.A Solas Amita 17" should work well.
Just for fun you could measure the diameter.Measure from the center to the tip of a blade and double the number.

 

[JSMoore]

Re: Prop for Evinrude 90 Special

Thanks, steelespike! I've been looking at the Solas Amita props. I'll probably be ordering one of them.

 

[steelespike]

Re: Prop for Evinrude 90 Special

Be sure to let us know your results.