Same thing different prop !!

[kenmyfam]

Using a 14" X 19" and getting 46 mph at 5500 rpm. Alternate is a 14" X 17" giving 46mph at 6200 rpm.
Does not seem to matter what load I have (1 to 6 people) and whatever gear on board. Gives the same speed and holeshot !!
Could it maybe need a de-carb ?? to see a difference ?? I am new to this boat this year so I have nothing to compare to. It is a 16.5 ft Doral with140hp 1985 Johnson.
Thanks in advance.

 

[walleyehed]

Re: Same thing different prop !!

I think to increase your speed you will need to either raise engine or try a higher quality prop.
It's not real un-common to see the same speed with 2 different pitches..
Almost 9% slip with the 19 and around 10% with the 17.
With an increase in your X-demension, I think you'll see a rise in MPH and RPM, but I think you'll need a better prop to get more, although 9% is not bad, you should have gained around 400+/- in theory going to the 17 if it is of the same blade design....obviously it's not, because you gained 700RPM, but no gain in speed.
Maybe you've listed the P/N's before, but could you give some info as to make and model of each prop?