Will rudder effect prop output

Hi every one new so this is my first input. I have recently done up a Dockrell 22. She has come up like new and although I have removed her dropping dagger board she sails fantastic. Though she seem to be really slow under power. I was wondering if the prop being about 2and half inches thick with very little point to front, it could effect the power from the prop. Or do I just need a larger motor, I am using an Evendude 4.5hp. the speeds I get seem very slow even when I reve he up. Thanks in advance for any help. Cheers Pete

you can get some drag from the rudder, but it is usually minimal, More likely you need a different prop and possibly a larger motor, but I would start with the prop first… Determine what diameter and pitch you have and then go from there, basically you will not be going over 5 knots or so at full power, but what you need is to move more volume of water, usually a larger diameter and lower pitch will accomplish this. Bearing in mind what you have and what max rpm is on your Evendude one inch drop in pitch will equate to 100-200 rpm rise and one inch increase in diameter will drop the rpm about the same amount. Obviously, this is limited physically by the motor itself. If Evinrude has a sail drive (motor purpose built for being a kicker on a sailboat) check out the prop specifications and that may be a solution for you, (if it has the same HP motor)… Just remember, no matter how much power you add, you will never get much over hull speed. Thanks Mark