Blade vs old 2 blade perf

[slayer2]

Looking to see what kind of performance ; plus vs minus by going from a factory 3 blade 12 3/4 dia 21deg pitch to a stainless 4 blade 13 dia 21 deg....

Anyone ?

Installing motor is a merc 125 2 stroke

 

[jimmbo]

Re: Blade vs old 2 blade perf

so what is it? title of post "Blade vs. old 2 blade perf" has no meaning as to what is in the post



BTW pitch is measured in inches not degrees

Also there were 6 cylinder inline 125hp and 4 cylinder 125hp.

What is is used on?
current rpm?
engine?
gear ratio?

 

[slayer2]

Re: Blade vs old 2 blade perf

The 2 blade topic was a typo

 

[slayer2]

Re: Blade vs old 2 blade perf

so what is it? title of post "Blade vs. old 2 blade perf" has no meaning as to what is in the post



BTW pitch is measured in inches not degrees

Also there were 6 cylinder inline 125hp and 4 cylinder 125hp.

What is is used on?
current rpm?
engine?
gear ratio?

The boat is a Crestliner 1750 fish hawk

Motor is a 4 cyl 125 hp two plus two 2 stroke

Current prop is alum oem 12.75 x 21 3 blade

Looking to upgrade to a 4 blade 13 x 21 ss

5600 rpm currently wot

Gears unknown

 

[jimmbo]

Re: Blade vs old 2 blade perf

well your engine is over revving by 350 rpm. The WOT range is 4750 - 5250. Adding an extra blade will certainly slow it down as will the extra diameter. I've never ran a 4 blade so I can't offer any wisdom/criticism regarding them. Others will chime in

 

[slayer2]

Re: Blade vs old 2 blade perf

The boat is a Crestliner 1750 fish hawk

Motor is a 4 cyl 125 hp two plus two 2 stroke

Current prop is alum oem 12.75 x 21 3 blade

Looking to upgrade to a 4 blade 13 x 21 ss

5600 rpm currently wot

Gears unknown

Ok then... That 5600 is when trimmed up as much as possible without trimmed out too much if that makes sense.

 

[steelespike]

Re: Blade vs old 2 blade perf

I don't understand,You want us to guess your results if the motor isn't trimmed up to its best setting?
While your info is spread throughout the thread it would be nice to have it in an orderly fashion based on the questions in the stickys at the top off the prop forum.
We need to evaluate your present setup and performance. We need the year the motor in order to pin down the gear ratio.