Prop spinning out on a 45 Honda

[71chapparal]

Hi, I’m hoping somebody can help me out here. I have a 45 hp Honda outboard, which the prop is spinning out while travelling half speed and three-quarter speed. I’ve tried another new prop because the old one was separated from the rubber bushing. The motor is on a 20 foot fibreglass open boat. And I replaced the old prop last year. The prop I currently have on there is a three fan 11 1/4 x 13 pitch which is what the manufacturer calls for for that engine. Any suggestions will be helpful like if I should try a different prop size for that boat

 

[airshot]

The mfgr can't call out which prop you need without knowing what boat the motor will be used on. They sometimes make a general size recommendation to get folks started, but a real RPM reading at wot is needed to know what changes are needed to match the application.

 

[Texasmark]

SWAG: Boat is barely on plane if at all. Engine height may be too high for the engine boat combination. Prop is sucking air rather than water due to increased load.....point of least resistance. Once you determine WOT RPMs, if below the top end of the recommended RPM range, dropping pitch should help the problem, lowering the engine probably is not practical but a Dolefin or Whales tail, would help the problem of sucking air as the "anti-venilation plate" area has increased immensely.