Help with prop selection please

[Magnumu]

We have a Quantum 1800 xb (Fish and Ski), listed at 1625lbs, Has a 1991 force 120 hp outboard mounted. We are running 44 mph on gps with light load. currently has a 13x19 ss prop. Last time out was the first time that rpm gauge worked "correctly" It looks like its right at about 600 rpm ideling in gear, (1,000 in neutral) and if correct over revving to over 6,000 at wide open throttle. Does the speed sound right for prop/rpm/weight? If so should I go to a 21 or 23 pitch to bring rpm back to acceptable range? Currently very quick to plane, just worried about over rev, I don't believe there is a rev limiter on this motor?

Thank you

 

[Sea Rider]

Need to know excact factory stated min-max wot rpm range. How many boaters do you usually go boating with ? load will vary max wot rpm. Boating lightly loaded and say 3-5 up are 2 different scenarios if like running full hammer down. Depending on how much less wot rpm need to reduce a 21 would be right. a 23 will reduce rpm too much towards lug side.

Happy Boating

 

[Magnumu]

Not sure on factory max for motor. I believe it is 5250-5000 based on what I can find. Typical use will be fishing with 2 on board.

Thanks

 

[Sea Rider]

Wot rpm is 5250-5500. If achieving 6K with 2 up and fishing gear, OB is over revvving 500 rpm. If we go by the rule of thumb that states losing 200 wot revs per 1 less pitch, then a 21 should be right. As this is not exact rocket science a water test will be needed to confirm that.

Check with 3 up and fishing gear how much wot rpm is decreased ?

Happy Boating