new prop-3 or 4 blade

[kopy kat]

Still thinking about a new prop--going from a 17P to a 15P (I boat on Lake Tahoe at 6225 ft elevation) in order to bring my rpm up closer to the 4800 range---but I still have yet to find a definate answer as to how many blades- 3 or 4.<br /><br />My 21 ft. SeaRay BR wieghs close to 4,000 lb loaded, with a Mercruiser 350EFI Alpha 1 set up.<br /><br />If I order the Mercruiser SS 4 blade, any idea as to which pitch to get, and any idea as to effective top end speed? I currently top out at about 42 mph at 4400-4500 rpm.<br /><br />Thanks in advance for the responses. Kopy Kat

 

[flashback]

Re: new prop-3 or 4 blade

the only thing i can tell you is the 3 blade is more efficient than 4. actually. 1 blade would be better than 2 except for the fact that it whould vibrate too much. more blades, smoother but less efficient ............good luck............

 

[Boatist]

Re: new prop-3 or 4 blade

Kopy Kat<br />I actually think 4 blade more efficient but also has more drag. I can not help with pitch from a 3 blade to 4 blade. I would call a good prop shop. I can tell you 4 blade will have better hole shot but less top end. So I guess depends on if you are looking for hole shot or top end.<br /><br />Miss Budwiser has a 2 blade prop.

 

[Spidybot]

Re: new prop-3 or 4 blade

Props are always a blend of compromises. Drag, lift, shot, grip, cavitation, ventilation, speed etc.<br /><br />As you've already defined one of your goals to be more rpm you need to decide what other characteristics you are looking for. <br />Your boat use and the waterways you run counts too.<br /><br />This previous post offers plenty of info.