Well folks I did it, finally got my boat. New to me, a 2000 Javelin 19' Renegade FS. 74# Evinrude trolling motor, Fuel injected Evinrude 150, 21" and 24" Raker props, dual bank charger, Lowrance X-28 on the bow, X-65 on the dash, Zercom flasher in the dash w/temp, and hydraulic steering.

The motor currently has the 21" prop mounted, and will crank out 62 mph at WOT and about 5100 rpm. What can I expect the  24" to do, speed and RPM?

Now if I can just learn how to catch those goofy little swimmers.

I'll met you at the dock at 5:30  

First you need to find what's causing the bad numbers in your setup.  At 5,100 rpm, the max speed a 21" pitch prop will give is 54 mph with zero percent slip which is not possilbe to obtain, usually about 15% is more of what the slip factor will be.

If the tach is reading right and the motor is really only turning 5,100 rpm, then I don't think you will even get out of the hole with a 24".  The is already not turning near enough rpm.

I am heading to the lake again today, will do some experimenting. The speed is indicated from the speedo which is a pitlot tube type, it very well could be off, i'll take the gps with me today. I'lltake the 24 with me too and check out what it will do.

My speedometer was off by over 10 mph when I checked it with my GPS.

GO BIG RED

I'd say your speedo is just a bit off  There's always the possibility that your tach is slightly off as well.  A 150 with a 21" Raker should turn more than 5100rpm.  You didn't say whether or not you have a jackplate installed.  If your readings are correct (rpm), you may need to raise your engine height.  BTW, Rakers only come in even numbered pitches so I doubt that your's is a 21 (if it's a Raker).  The OMC 4-blade props come in odd number pitches.  Just remember to trim out your engine so that the "roostertail" doesn't go beyond the height of the engine cowling.  Anything more than that and you're wasting power.

I've owned a few 150's over the years and I've never had any problems hitting max RPM's running any 21p prop on one.  You've either got a tack problem or that 21p prop isn't what you're thinking it is.