3 Blade vs 4 blade props

mkuehnl

Petty Officer 2nd Class
Joined
Feb 22, 2002
Messages
103
I have a 350 Mag tournament ski, inboard, ( Sea Ray - Spitfire) and I am considering changing the prop from a 13 pitch 3 blade to a 4 blade. What do I need to consider, regarding pitch, when I go from 3 to 4 blades?
 

Elk Chaser

Petty Officer 2nd Class
Joined
Jul 29, 2003
Messages
186
Re: 3 Blade vs 4 blade props

DETERMINING THE CORRECT PITCH:<br />Adding 1 inch of propeller pitch will reduce wide open throttle rpm by 150 to 200. <br /><br />Subtracting 1 inch of propeller pitch will increase wide open throttle rpm by 150 to 200. <br /><br />If you are upgrading from a three blade to a four blade propeller, remember that a four blade propeller generally uses up to 50 to 100 rpm more than a three blade prop with the same pitch. <br /><br /><br />4-BLADE PROPELLER FACTS:<br />Plane the boat faster than 3-blade propellers <br />Keep the boat on plane at a lower speed <br />Give improved mid-range speed at the same rpm as a 3-blade propeller <br />Provide quicker acceleration than most 3-blade propellers <br />Run smoother than 3-blade propellers <br />Have better holding power in rough conditions <br />are less likely to ventilate in sharp turns <br />provide better low speed handling
 

kopy kat

Seaman Apprentice
Joined
Mar 21, 2003
Messages
48
Re: 3 Blade vs 4 blade props

Better yet-look at Mercury's Stainless Steel High Five 5-blade. My 21ft SeaRay comes out of the hole real nice and smooth. :p
 

mkuehnl

Petty Officer 2nd Class
Joined
Feb 22, 2002
Messages
103
Re: 3 Blade vs 4 blade props

Graet advice - does that hold true for inboards(Ski boat) as well?
 

tommays

Admiral
Joined
Jul 4, 2004
Messages
6,768
Re: 3 Blade vs 4 blade props

we have a correct craft and it is so compleaty different than and i/o boat because of the center mount engine and hull design thay really go through the water rather than rise up on plane to keep the correct ski wake<br /><br /><br /> i would talk to a prop shop that works on ski boats or people in the water ski comunity<br /><br />tommays
 
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