TOPIC: another newbie question

I took out my boat today and something seams wrong. After a carb rebuild abd fuel pump rebuild i swapped the prop toa spre tht came with the boat. Old prop 10x1x10 new prop 10x1/4x10. Boat ran fine and started great but would not go over 8 or 9. She should have gone much faster. I dont know much about props but could this be the problem?
She ran good. Plugs did not foul and no starting or flooding issue.i dont even think she was missing just no acceleration.if not the prop what can i check? Now that i see it in writting i dont think the prop size if differant enough to notice any performance issues so where do i start?

Just a thought,
Since my prop is pin driven slippage should be a non issue. I changed the oil in my lower unit but not being selectric i should be safe with the oil. I am thinking i still have a fuel delivery issue. Wouldnt that manifest itself as a lean condition? You think maybe its the hose?

a prop spinning on it's hub is fairly common....mark the hub and the prop and see if she moves under power...john

I put my other prop back on and she acted a lot better in the test barrel. Put her in gear and she threw water all over.i am feeling confident but i thought if the prop was slipping it would rev too high but she didnot act that way. Can someone help me understand the relationship between the prop and the effect on the rpms? Sometimes it helps to know why things work.