Prop issues

[Berlin boater]

I have s 23’ south bay pontoon with a 115 4 cycle mercury turning a 13.75 diameter and 13 pitch prop. The boat runs fine until about 3/4 throttle 18 mph. At this soeed if I try to go full throttle it cavitates. Do I need more pitch? Diameter? Both? Hub is fine and trimming up or down doesn’t help.

 

[alldodge]

Welcome,
Cavitation would mean the prop needs to be lower. Can you lower the motor any?

 

[Berlin boater]

Welcome,
Cavitation would mean the prop needs to be lower. Can you lower the motor any?

No, the motor is as low as it can go

 

[alldodge]

If you didn't buy it new, then the leg may have replaced with shorter one. Right now I don't know enough

 

[Faztbullet]

Your really under powered on a 23' so a prop like below is best.

Turbo Pontoon 1 from BBlades Professional Propellers

bblades.com

Workboat | Barge | Pontoon Boat Boat Propellers

Patented Reverse Hook Cup Propellers for non-Planing Pontoon Boats, Workboats and Barges which gives up to twice the reversibility, enabling boats to turn more effectively, stop forward momentum and control the boat in reverse

propcomarinepropellers.com