help with pitch/prop selection

bmurray

Petty Officer 2nd Class
Joined
May 16, 2002
Messages
152
I have a 17' Charger fish&ski with a Johnson 150hp. What is the best pitch for this boat to keep it in the best operating RPM. I like top speed and want to pull tubes for the kids. Right now I have the factory aluminum 14.25 x 21p, is this a good setup? Thanks
 

thosch

Petty Officer 3rd Class
Joined
Sep 3, 2001
Messages
90
Re: help with pitch/prop selection

What rpm's are you getting now at WOT?
 

bmurray

Petty Officer 2nd Class
Joined
May 16, 2002
Messages
152
Re: help with pitch/prop selection

I just bought the boat from my friend, but the last time we ran it it was almost 5800-6000 I believe, but not 100%.
 

MGuckin

Senior Chief Petty Officer
Joined
Jun 10, 2001
Messages
760
Re: help with pitch/prop selection

You did not specify your model year of the motor.<br />On the port side of motor at the transom should be a plate with suggested operating range. On my 84 150 it is 4500-5500. If that is the same as yours, you are revving too high. Increasing your pitch will reduce your rpm at wot and increase your top end speed. 1" of pitch = about 200 rpm.
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: help with pitch/prop selection

You didnt mention what kind of load you have to get to 5800. If thats a light load, and your rpm really is 5800 then you are right in the ballpark. Give us you EXACT RPM and EXACT speed with an average load and we can calculate slip. <br /><br />Check your tach and make sure it's set on position 6. <br /><br />Good luck!
 

MGuckin

Senior Chief Petty Officer
Joined
Jun 10, 2001
Messages
760
Re: help with pitch/prop selection

Dhadley,<br />Isn't 5800 a little high? Not really hurting but a waste to rev that high on an omc v6? He asked for best not max. <br />Keep in mind I am still learning. <br /> :)
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: help with pitch/prop selection

We have found that motors (like this one) propped out at 5800, with an average load, coke up less, have a better holeshot, get better fuel mileage and live longer. <br /><br />Now -- the trick is to do it with set up, not just a prop change alone. If a boat like this one only turns 5300, it is more desireable to increase RPM by increasing the X dimention (raise the engine on the transom) rather than simply going to a smaller prop. If this boat truely turns 5800 with an average load, I would play with the X dimension and hopefully go to a higher pitch/better design prop to achieve more speed and efficiency.<br /><br />Fun stuff!
 

MGuckin

Senior Chief Petty Officer
Joined
Jun 10, 2001
Messages
760
Re: help with pitch/prop selection

I don't want to impose on this topic but I have questions about x factor determination for my Starcraft. <br />I will start another topic.
 
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