Prop Pitch Issue.-

[Sea Rider]

Was ordering a 3 blade 3 X 9.2 X 8.5 (pitch) but impossible to get, was thinking about using a 3 x 8.9 x 8.5 (pitch) both are alum cupped props. What would be the pros and cons or whatever it achieves having a slight less diam on the second prop. Will hole shot remain same, which one would have slight better top speed on my combo bare bone loaded with just solo driver ? Thanks.

Happy Boating

 

[Maclin]

More diameter will keep the slip% lower when the prop is trying to push a heavy load, like a pontoon or barge, etc. But the difference you mention is only .15 at the blade tips, and the heck, even shape of the blade on the smaller prop could make up the swept area difference from that small of a diameter change.

What craft are you talking about, the one in your sig block?

 

[Sea Rider]

It's a 4.50 Mt Rib with a Tohatsu 2 strokes 18 HP, with stock prop 3 X 9.2 X 9 pitch achieves 50 rpm less that its factory wot range which is 5800 rpm, that's barebone loaded with just driver around 400 Kg. Changed to a 3 X 9.2 X 8 pitch and engine over revs to 6250 rpm which is + 500 than "rule of thumb", ideal would have been an 3 X 9.2 X 8.5 to decrease just 200-250 wot revs, but impossible to get, that why was asking, the only available is the 3 X 8.9 X 8.5 pitch

Have 2 options (1) go for a 3 X 8.9 X 8.5 (2) have factory delivered 3 X 9.2 X 9.0 pitch re pitched to 3 X 9.2 X 8.5 pitch. The issue is that don't know if first option will fit my current engine's prop shaft as it's from another HP model engine. We're talking about standard cupped alum Tohatsu props.

Will you need any other info to evaluate the combo, I'm just doing a prop maximization to be where I want to be. That's half of the total over revving, know that as soon more load is added rpm will drop accordingly. Thanks,

Happy Boating

 

[Sea Rider]

3 X 8.9 X 8.5 pitch is not compatible with a 18 HP OB as it's a 9.8 HP prop, so this option is discarded by its own nature.. BTW, does someone knows or have worked with James Propeller & Parts in North Texas ? the plan is going for the seconf option, send them a brand 9 pitch to have it repitch to a 8.5.

Happy Boating