O’Day 34’ Original Prop Specs?

[Quadrille in JB]

My 34’ O”Day has obviously had the propeller changed by a PO. It has a 25 hp Universal #5454 and currently has a 12x16 2-bladed prop which limits the WOT to 2400 rpm. The engine seems to work very hard at >1700 rpm. It starts and runs great but when I rev it up in neutral after a hard day of crossing and fighting the Gulf Stream it spits out a lot of black unburied fuel. I’m concerned that this low rpm is limiting my available hp and hurting my engine. When fighting current, waves and wind I could use all the available hp I can get.
I would like to replace the prop with the proper diameter and pitch that will get my engine back into a better cruising rpm range. Any help will be greatly appreciated. Thanks in advance.
Bill in JB

[Quadrille in JB]

I found the original owners manual that came with my boat and it shows that the current propeller is the same as the original equipment.
I don’t understand why this boat was delivered with such an over pitched prop.
I’m currently bidding on a lower pitched prop which hopefully will help get the engine back up into its proper operating range.
Any ideas or suggestions will be greatly appreciated.
Thanks,
Bill in JB