WRONG PROP SIZE?

[gearyjo]

Had spring tune-up on used boat that I purchased in fall. Mechanic said that the prop was the wrong size. <br />Current boat specs are : 19' 1985 Grady White Tournement, 1985 140 hp johnson, WOT 4600 rpm. speed 31 mph at WOT (with 3 people on board) using gps, current prop size is 14.25x21 SS <br />Mechanic says rpm should be 5500 at WOT. <br />Thanks for the help.

 

[DJ]

Re: WRONG PROP SIZE?

gearyjoe,<br /><br />Yes, 4500 rpm is too low for WOT. Should be somewhere between about 5300 and 5600.<br /><br />You can figure that each one inch in prop size (pitch) equals about 200 rpm.<br /><br />A 21" is a bit "steep" for your set up. I would look into a 17" to 19". Your low end will improve dramatically with little or no loss in top end.