Your boat is never going to turn a 23 pitch with a 150 4-stroke. There are larger BC boats out there with 100hp more that cannot turn a 23 pitch prop to full rpm's.
Take all of the weight out of the boat...this is the first thing to do then run the boat and see how it performs. if you have all of this weight in the front and are turning a 23 pitch that is why things are the way that they are.
Don't know about a Margay but my Caracal won't even get onto pad until I am hitting close to 5000 rpm's and that is with little to no weight in the front.
1 pitch of prop is approx. 200 rpm's so you do the math. The 4 strokes have larger gear cases which have more drag. you are over 1000 rpm's off and are not getting on pad which is where the speed comes in. Stop focusing on the amount of pitch of prop you need to run as the more rpm's the HP you make.