Gear ratio to prop size

[rockdog57]

Is it possible to make up the difference of a 162 gear ratio outdrive. To get it close to what a 147 ratio would be by changing props to a more aggressive pitch? Not sure that makes sense but, I'm changing out motors in my boat from a 200 horse 5.0 to a 300 horse 5.7. I really don't want to change top ends on my outdrive if possible. Is it doable with prop changes?

 

[SkiDad]

definitely doable. Just use your current prop after the change and post your numbers. You might have to change 4" in pitch with that much extra power.

 

[Bondo]

Ayuh,.... It depends on what pitch yer startin' with,.... There's only a narrow window of available pitches, 15" to 23" or so,.....

If yer startin' with a 15" or 17", Ya, probably,....

If yer startin' with a 21" or 23", Nope, no more pitch easily available,....

The Boss had a barge with a 4.3l in it, 'n We swapped in a 350,... Had to use very hard to find 25" prop on it, 'n a 27" mighta been better,....

He finally blew the drive, 'n I put the right ratio on it,....

 

[rockdog57]

Ayuh,.... It depends on what pitch yer startin' with,.... There's only a narrow window of available pitches, 15" to 23" or so,.....

If yer startin' with a 15" or 17", Ya, probably,....

If yer startin' with a 21" or 23", Nope, no more pitch easily available,....

The Boss had a barge with a 4.3l in it, 'n We swapped in a 350,... Had to use very hard to find 25" prop on it, 'n a 27" mighta been better,....

He finally blew the drive, 'n I put the right ratio on it,....

Yeah, I'm using a 16" right now. So I have room to move up.

 

[smokeonthewater]

More blades will help too.

 

[rockdog57]

OK, I am in the middle of my motor swap and ran into a surprise. The ratio on the out drive is stamped 184. So now I've gotta make up even more ground to make compensation. Is this is still doable with a prop change? I realize that the shafts will be spinning faster in t he out drive. Will this hurt anything? Is there a chart somewhere that might show comparable combos? Like say a 150 ratio and 19 pitch prop would be the same as a 184 ratio and a 24 pitch prop- don't know if that is even close.

 

[Maclin]

What size boat is this?