Gear Ratio Debate 1.62 vs 1.75

[LakeFever]

I believe that when operating somewhere within the *intersection* of the *optimal efficiency spectrum* of the hull (at speed), the prop (at speed) and the engine (in its powerband) that the gear-ratio differences can be neutralized with prop pitch changes (holding prop slip, efficiency equal, in theory). But, boats don’t always operate in that narrow intersection of hull, engine and prop efficiency!

I believe that the lower gear ratios have a distinct advantage in the transition from idle to planing especially. When you begin to spin the prop up to plane the boat, it’s mostly prop slip on these lightweight performance hulls. When you bury the throttle to get the boat on plane you are winding the prop up (winding up a heavy 14-17 inch stainless steel prop through a very dense liquid) through a period of heavy drag and heavy slip, where in my opinion the torque from the lower gears has a distinct advantage.

Very interesting and certainly you present an angle that does lean weight towards liability. I use the word liable because its very challenging to isolate the effects of each component in a dialogue and liable is not absolute but carries enough weight to swing agreement. What im taking out of this is the taller the prop pitch, the more liable the real world performance becomes to each blade of the prop per revolution. The shorter the prop pitch the less liable each blade becomes because it has more opportunity to work within the engine RPM limits and increases odds to swing liability back in the favor of the engine, hull etc.

Make sense? The outcome is dependent upon previous gains where liability is concerned. If you have a prop that is ideal for certain hull and engine but the gear ratio is not providing the optimal range for this prop then the gear ratio is the performance advantage but soon as you provide it the prop once again becomes liable for performance because we could always as it to do more until the hull/weight gets in the way and liability shifts again. This is a very interesting dance.

Somewhere a millions posts ago it seems the correct answer was provided. Add more horsepower until goals met

[Captaincj]

Yeah that, or I'm just saying that off idle the torque to the propshaft of the lower gears helps the engine spin up a heavy prop that is mostly slipping in a very dense liquid. The prop is working very inefficiently at this point, and the differences in propeller pitch are not enough to overcome the shorter gear ratio. At speed, within the intersection of the hull, prop and engine efficiency range, the differences can be equalled out.

[Captaincj]

And, to much lesser degree, props of higher vs lower pitches have slightly different optimal speeds where the prop can be at peak efficiency. So depending on how one boater uses his craft (what speed range they are using the butt-dyno) the peak efficiency of either higher pitch or lower pitch props will win. Even when the "math" says they are equal.

Boater A who uses his craft to accelerate from each winding River bend to the next will have a different experience than boater B who rips at max velocity for 10 miles at a time.

My opinion of course.

[2.5-21]

Simple question here......
does anyone know or have gears at their disposal to know how many teeth are on the 1.62 and 1.75? pinion and drive....