Original Prop For 26' Pacemaker Sportfish?

I own a 1978 26' Flybridge/Sportfish Pacemaker with a single 350 CID (260 HP), 1.52:1 transmission ratio. Would anyone know which size prop was originally provided by the manufacturer for this boat? Currently running a 15 X 11 medium cup 3-blade and is still slightly overpropped. WOT is 4000 RPM. Thinking I should be at about 4400 RPM WOT. This boat still don't have the speed other Pacemaker owners claim to have with same model, but most I've researched have a 1:1 tranny ratio. Thinking I should be running a 15 X 10 3-blade.

Would really like to know what was originally supplied by Pacemaker for this setup.

Thanks for any help.

Bob

 

Now running a 15 X 10 Medium Cupped wheel and hitting 4,300 - 4,400 RPM at WOT. Picked up a couple knots at WOT to 22 knots, boat has more power running head on into 2 - 3 footers, and engine now sounds much smoother thru all ranges (no more straining or lugging/growling).