sold Prop Swap 23p for 21p Stainless

[matsmad]

As the title says i have a 23p stainless prop in excellent condition wanting to swap for a 21p stainless as the 23 is a little too big for my boat wont quite rev out. To suit a 150hp Johnson V6 1993 model. Cheers :-)

[mick fillet]

a 23 pitch wat the hell :silly:

wats ya rpm with the 23 pitch

[haines490slc]

I need to drop from a 21 to a 19 or a 20 four blade

[mick fillet]

I need to drop from a 21 to a 19 or a 20 four blade

noooo because of the extra blade added it create alot more inertia. so you probly best droping to a 17 if your goin 4 blade. or get a 3 blade 19 and get it cupped that way you still will be known on the water as "fast eddie" but seriously down size the prop and cup it

[haines490slc]

We tested a four blade 21 inch and could only get 5 grand rpm, with my current 21 inch, I can only get 5300

[matsmad]

a 23 pitch wat the hell :silly:

wats ya rpm with the 23 pitch

5200rpm at 91kmh with the 23p. I run a 19p for waterskiing etc it hits 5800rpm at 82kmh. If I go a 21p I think it should still hit 5600-5800 which would be good. The motor is on a 16ft fibreglass bowrider.

[mick fillet]

get anther 19 and get it cuped to a 20. the 19 might have a slightly smaler dia but by cupping it your giving it top end legs

[matsmad]

get anther 19 and get it cuped to a 20. the 19 might have a slightly smaler dia but by cupping it your giving it top end legs

I thought about that. Would cupping make that much difference?

[mick fillet]

youll probly find you might even go quicker on top end, and out of the hole shot is absolutly insane theres a few reasons for this.by cuping a prop your creating the prop to now have a cork screw effect so its really biting the water and keeping the water on the face of the blades. where as on ya stocko props water does seem to find its way off the blade before it has exited the tip of the blade.

so by making more water stay on the face of the blade this creates more friction infact so much friction that the water acxtually boils on the outer tips of the blades but this only happens under extrem load like out of the hole or some serious off shore work in the biger stuff where you use the throtle in the low - mid range rpm.

now from the exta friction being created theres now air bubles that form from the tip back on the prop cased from the boiling water and because of these air bubbbles on the face of the blade friction on the prop is now reduced allowing the engigin to spool up to full rpm instantly but because the prop is cuped and has the cork screw effect and has plenty of bite the end result is enormous thrust and propulsion.