getting the right prop

[ringmaster]

i hope this is in the right spot. i have a 1977 sea ray 24ft 233 pre alpha out drive. the prop that is on there now is a 15 1/4 diameter with a 19 pitch. it gets out of the water excelent and when im on plane all trimed out i can get 38-40 mph at 4000 rpm's. i know my rpm's are low for the speed from what im told i should be around 4400-4800. i cannot check with a gps cause i dont have one. i also know the tach is old and will be replaced this winter. what im asking is what would be a excelent prop to use to get the rpm's where they should be and maintain 40 mph. the prop i have now is shot thats why i need to replace it. thanks

 

[rndn]

Re: getting the right prop

For every 1 inch change in pitch the rpm's change by about 200. So if you have a 19 inch and change it to a 17 inch your new rpm's should be around 4400. 2 inch chnage move rpm's by 400.

 

[ringmaster]

Re: getting the right prop

i understand how the pitch and rpms work but will i beable to keep my 40 mph mark?

 

[rndn]

Re: getting the right prop

Don't know for sure but you should keep the same top speed while allowing your motor to live a long healthy life Over propping your motor as you have now will significantly reduce the life of your motor.

 

[ringmaster]

Re: getting the right prop

i just dont want to go to low i do have to get a new tach first then the prop.