1999 Mercury 300 pro max

**George Paul** · 07-23-2017, 05:10 PM

Can anyone tell me what RPM I should run a 1999 Mercury 300 pro max to get the maximum horsepower. I am currently running 96MPH with a 21 Liberator at 5200RPM. Is 5500 the target?

Thanks,

George

**kct11** · 07-23-2017, 06:57 PM

Target 6000 rpm. Your numbers don't quite make sense. With a 1.62 and 12% slip to run 96 at only 5200 you would be swinging almost 36 pitch.

**JPEROG** · 07-23-2017, 07:13 PM

I am pretty sure that they have a 6400 limiter and make peak power at just shy of it. The X motors like a few hundred more.

Joe

**George Paul** · 07-24-2017, 07:46 AM

I have been clocked by another tunnel and verified the speed. I am now thinking the tach may be off???
Thanks,
George

**whipper** · 07-24-2017, 08:29 AM

You can Velcro a hand held GPS to the dash or something like that or get a GPS app for your phone for free they are fairly accurate also. Once you have the speed you,ll know what more to do for setup. Its pretty hard to accurately tell how fast your going buy another boat beside you. Especially if he is using just a speedo. No speedo is accurate after 65 or 70 mph unless a GPS.

**George Paul** · 07-24-2017, 08:49 AM

Thanks we are both running GPS speedometers so the speed is correct. I read that a 300X makes maximum power at 6400 but my motor is just a 300 pro max and is a 1999 so maybe the older motors run lower RPM?
George

**kct11** · 07-24-2017, 09:07 AM

I have a lot of hours on a 300 promax. I would shoot for the 6000+- with when running larger pitch props. They have a soft then hard limiter. The soft one will kick in around 61-6300. At that point it cuts back power. I noticed it when running high pitch props. Put a 28 or smaller and it will buzz past that pretty good up to the hard limiter. It has decent torque so take advantage of that.