Help finding a higher pitch prop.

[Thompsoncustom]

I was wondering if someone could point me in the direction of a high pitch prop than offered from the factory. I am currently running a solas 10x15 pitch alum prop on my modified johnson 20hp and it plains instantly so I assume I could bump up to a higher pitch for more top end speed. I bought a tach last year but never did get it running right so I figured if I could find a 17 pitch that would be a good place to start untill I could get the tach working or get a different one. I trashed my 15 pitch last year so I have to get a replacement before I can do any testing.

 

[Sea Rider]

Is OB running at its max wot rpm range which isn't known ? . Install tach or buy a Hardline Hour/tach before venturing playing with prop pitches blindly..

Usually one should start taching delivered standard prop, then go from there maximizing pitch if max wot revs are no bueno..

Happy Boating

 

[steelespike]

It does seem reasonable based on your 15" hole shot Get us your lightly loaded wot gps speed,year of the motor,remind of the prop size.A good prop shop could modify your prop as much as 2" and some cup could be added.

 

[Sea Rider]

Without a tach installed, it's a wild guessing playing with prop pitches,adding cup before testing delivered one. That's propping right if you want to take the max HP out of underpowered OB's at their max factory wot rpm range..

Can't have both worlds on a single prop, faster hole shot traduces in slight less top end speed. less hole shot traduces on slight more top end speed.

Happy Boating

 

[Thompsoncustom]

Understood but at this point I don't have a prop at all to do any testing with. I figure if it preformed so well with the 15 pitch it hopefully won't become a dog with a 17 but it if did I'd just buy a 15 too and swap it out when needed I just can't seem to find any prop for this motor above 15.

Boats a 98 14ft alumacraft modified V, OB motor is a 90 johnson 20hp with the 35hp conversion.

Best speed on got lightly loaded (just me and gear) was 32mph great thing with the current prop is if I add another guy and some more gear it doesn't slow it down hardly at all.

 

[Bondo]

I just can't seem to find any prop for this motor above 15.

Ayuh,.... So buy a 15", 'n do yer testin',.....

If it needs more pitch, a prop shop can beat in another inch,....
If that ain't enough, they can beat in more cup to bring the rpms under control,.....

 

[steelespike]

Understood but at this point I don't have a prop at all to do any testing with. I figure if it preformed so well with the 15 pitch it hopefully won't become a dog with a 17 but it if did I'd just buy a 15 too and swap it out when needed I just can't seem to find any prop for this motor above 15.

Boats a 98 14ft alumacraft modified V, OB motor is a 90 johnson 20hp with the 35hp conversion.

Best speed on got lightly loaded (just me and gear) was 32mph great thing with the current prop is if I add another guy and some more gear it doesn't slow it down hardly at all.

It appears the 20 and the 35 use the same props. the 20 may have a 2.15 gear ratio the 35 may have a 1.91. You may be able to change your gear ratio.
I think the 20 rpm range is 4500 - 5500 the 35 5200 to 5800. Guessing some of the numbers 2.15 ratio,15",10% slip, 32 mph = 5380 rpm.
Is the speed by gps?It is said that cell phone gps may not be accurate do to using cell tower location instead of satellite.
You can check your gear ratio by removing plugs and rotating the motor. Power head 2.15 for prop once,is 20 hp ratio.
You need to have a tach for the health of your motor. An induction tach will work.