Prop for DF90 Suzuki

[Valiant Knight]

I have a 5.2 meter Valiant PT RIB with a DF90 Suzuki (2006).
I bought the boat and engine in 2011 and the engine was fitted with a SOLAS Rubex 3*13.25*17 (aluminium) propeller.
Under light load I get 20 kts at 4000 rpm, 25 kts at 5000 rpm and 30 kts at WOT (around 6000 rpm) (speed comes from GPS, RPM comes from the engine display).
Since the recommended Max RPM for the engine is 5500, I am planning to change the propeller to a 19" one. I noticed current SOLAS Rubex are not 13.25" but 13.875" in diameter.
Any hints on the pitch, diameter and type of propeller?
I normally use the boat under "light load" in fresh water (lake or river).

Thanks

[RMS]

I have a suz 90 on a zodiac 5.50 which is actually 5.25 and it works well with 3 blade 14x 19 Ali prop. Good acceleration and about 37 knts at wot.