TOPIC: RPM/Prop selection Merc 650

First of all, let me say thanks again to everyone for their input on the "Ventilation Issue" thread. Really good info. I received my prop shaft spacer for use with the newer tapered thrust washer that is being used for the new Vortex prop I am installing. I've always used the 17p props that came with the boat. Since I am pitching down (13.5"x15p), what are the ranges to look for, as far as motor speed is concerned. I have a tach coming (should be here tomorrow or Monday), but I'm not sure what's too high or low.

ideally 5000 - 5500. at full throttle with your usual load.

Thanks, Dave. Found a manual that said 4800-5200. What is the redline/danger zone to avoid. I'm sure this thing has over revved in the past, with as often as the prop would break loose. Also, since I will have a tach on it, where should my RPM's at idle be. Have always thought my idle speed was a little high.

Don't twist it over 5500, the reeds don't like it and neither will you. Your 650 is a lover not a fighter.

Idle 750-800 in gear would be fine higher if needed.

That seems a little high. I was figuring somewhere around 550-600 in gear.

I think you will get some stalling at that RPM.