just another prop question......

[dutch135]

From all of the reading I can find online about props., and the proper ones, and pitch, diameter, etc.... here is a question that came to me. I run this 18ft SeaRay with the 135 v-6. The standard prop that came on the boat was the 19pitch, 14 3/4 inch stainless prop. I also have used a 17 pitch aluminum and like the hole shot better with that for skiing. But that prop is a little smaller in diameter, and doesnt' hold the water well in corners and rough water. (the stainless is a little better, but not perfect) My question is this,, because everybody says an aluminum prop flexes under load, (actually changes the pitch as it does) would I get a better hole shot from an aluminum 19 pitch than my stainless? If so, then would I maintain my top end speed (within reason) and rpm range at WOT? <br /><br />And for everybody that wants RPM's, here they are,,<br />19 pitch stainless WOT runs 5200 RPM<br />17 pitch aluminum WOT runs 5800 RPM<br /><br />Also, any thoughts on 4 blade or the new "Ballistic" props on the market?<br /><br />thanks again,,<br />

 

[Spidybot]

Re: just another prop question......

The only way to really get the best of hi and lo, is a switching prop. Expensive but classy. Shifts some 6" so you could have the hole shot of a 16 and the top end of a 22" or 17/23.<br /><br />Making use of prop flexing takes a lotta experiments as this is not a defined factor by prop manufacturers.<br /><br />Most enthusiasts concentrate on minimizing slip and best grip for trimming and cornering (+ raising outboards).<br /><br />You have to accept the fact that props always are a compromise between hi and lo (the reason for making the shifting type).

 

[dutch135]

Re: just another prop question......

Is an adjustable prop , the kind that switches,, are they something that I have control of the pitch? In other words,, can I have the pitch at 17, then at 20 when I want top end, instead of having it go all the way to its largest 23 pitch? <br />

 

[Spidybot]

Re: just another prop question......

The one I'm thinking of is adjustable but not by selection while on the way.<br />It gives you the low pitch for hole shot then shifts at a certain prop -rpm. The shifting point is adjustable. From tests I've seen it's quite impressive as you get a kick-in-the-a** hole shot (claims 20-30% improvement) and when the engine reaches higher rpm and he boat is planning you get hi-speed second to none.<br /><br />Even improves docking etc. as a low pitch is easier controlled when you need low speed.<br /><br />Comes in 13/19, 15/21, 17/23, 19/25 and 21/27 pitch and for RH rotation only.<br /><br />The shift is controlled mechanically by weights.<br /><br />It's a Quicksilver (Merc) product known as 'Power2 Variable Pitch Propeller' available for Alpha One drives (don't know about others??)<br /><br />Only drawback I've heard of (besides the price) is that the shift tends to get stuck if you leave it unused the water for long periods.

 

[dutch135]

Re: just another prop question......

so,<br />if i am looking for something like 17 then 19,,,, should i go with the 15/21 pitch ? and keep what i think are my best pitches right in the middle of the range? I'm going to have to research this a little more and see what the manufacturers say... thanks for the help!<br />

 

[Spidybot]

Re: just another prop question......

You should focus on the WOT as this range must be respected. You state 5200/5800 which puzzles me. In my book it says 4400-4800 which indicates you are way over the limit. If your rpm are true (tach error?), you should pitch up to 21 - a 15/21 if you choose the switching as one pitch up means approx 200 rpm down.