Proper RPM's on a Evinrude 1981 115Hp, with at 1978 Johnson powerhead.

[atktom]

I have read many posts on this and Dhadley says to run in 5800 to 6000 rpms. I have it on a 1978 Ranger, with a 13 X 19 SST prop and would run nicely at 4800 and could only push it maybe to 5300 max. So now I put a 13 X 17 SST on and it runs nicely at 5200 and can push it as high as 6000. Now I already blew up at 1978 70 hp Evinrude and I am really nervous running as high as 5800 +, so figured I would run it in the upper range of 5300 to 5000 (book calls for 4500 to 5500) and hope for the best. Looking to get other opinions to make feel good about what I am doing. Thanks

 

[jimmbo]

The manufacturer says 4500 - 5500 is the WOT range. There aren’t major differences between the years, maybe the linkages are different or timing spec. Both are crank rated. The 115 makes its best power around 5100 - 5200 rpm so you are close at 5300.
A 700 rpm change from a 2” pitch change does not sound normal. Was the 19 cupped and the 17 uncupped? We’re both props from the same manufacturer?

 

[atktom]

No both are just basic standard props. But the 17 was kinda bent on one blade and none of the 3 blades were at the same height, all were within 1 inch of each other. That being said I took it to the prop shop in Ft Worth and they corrected and balanced the prop. I have not had a chance to try it out yet, so it may drop a little on the rpm's.

 

[jimmbo]

"same height", "1 inch of each other" ?????

 

[atktom]

My bad. Before being repaired, the blades were not all the same height, but were with in 1 inch of the same height. Sorry for the confusion.