Need the Prop Gurus!

[racerone]

The decals on this 1977 motor say 115 HP.------Step #1 is to determine if motor is still producing that power.-----Then you can experiment with a tachometer to find correct RPM range on the boat.

 

[Sea Rider]

The decals on this 1977 motor say 115 HP.------Step #1 is to determine if motor is still producing that power.-----Then you can experiment with a tachometer to find correct RPM range on the boat.

How do you determine if such motor is producing 115 HP output cowl rated ? What about if that motor has always been over propped before and after complete rebuilt and previous or new owner never knew about it...

Happy Boating​

 

[tbetty]

Some body is telling you a story:

Go-Fast.com > Knowledge base > What is Prop Slip? > Prop slip calculator

Your slip is minus 15.....a screw turning in a block of wood is a slip of zero. Fast boats run in the positive single digits.

Could very well be so. Never checked tach but have seen higher rpm on motor with a 2 blade alu prop. showed in the mid 50s but not verified. Scary chine walk tho. Long time ago before gps. Running a 19p prop now supposed to be repitched to 17 . Gets me from fishing hole to hole and limited tube pulling, maybe correct on throttle openings. Never checked but compression is good on all and all close.