hi guys i have a 16' 1980 thundercraft with a 1977 johnson 140. with four people in the boat im getting about 68km/h. i just installed a tach today and did not know what the rpms were befor. i just installed a 12 3/4 with a 21'' pitch. there was a 13x19 prop on it befor but i never got to test it out as it was damaged. At WOT im only getting around 4600 RPM. what should i look for? should i change the prop back? im mostly using this boat for Tubing and some fishing. could there be a problem with the motor? Thanks!
