Pontoon prop selection

[JGator]

18' pontoon, 2013 50HP Yamaha 4 Stroke. The max RPM I see is 5000 to 5100 with a 11.6X11 prop and @ 19 mph with two adults, this is a new tach and correctly set for the motor. With 4 adults and two coolers we averaged 16 mph @ 4800 RPM. Both were fresh water trips. Thinking about going to a 12X10 prop to get the RPM closer into the 5000 to 5400 range. Am I going in the right direction? Should I simply leave well enough alone and stay with the 11.6X11 prop?

Jim

 

[steelespike]

I double checked, rpm on the F50 is 5000-6000.
I'm thinking you need a 9" pitch Should put you at "about" 5500.
Should keep you within rpm range as you add weight.
Top speed will probably be a wash but will feel peppier and speed should hold up better as you add weight.

 

[Sea Rider]

If you will be boating say with 3-4 member family, you could maximize prop to achieve middle 5500 wot parameters for that engine, engine will work nicely throughout the whole throttle range. When boating with less family members or solo, rpm should increase, in that case watch tach, throtttle down so not to pass 6 K.

Happy Boating

 

[JGator]

I double checked, rpm on the F50 is 5000-6000.
I'm thinking you need a 9" pitch Should put you at "about" 5500.
Should keep you within rpm range as you add weight.
Top speed will probably be a wash but will feel peppier and speed should hold up better as you add weight.

I did see the range, 50hp @ 5500. I did order the 12X9 prop. I should know how well it does this weekend... Thanks for the guidance.

 

[JGator]

If you will be boating say with 3-4 member family, you could maximize prop to achieve middle 5500 wot parameters for that engine, engine will work nicely throughout the whole throttle range. When boating with less family members or solo, rpm should increase, in that case watch tach, throtttle down so not to pass 6 K.

Happy Boating

Thanks for the reply!

We usually include Barley, a 60 lb dog, and two adults...on most every trip and can have as many as 6 or 7 when boating on the lake with friends. The old tach showed higher RPM so thought we were in range, but is was old and had other issues, like showing 1200 RPM on idle on a new motor which wasn't correct.

 

[JGator]

Went out last Saturday with new 12.1X9 prop, gained around 350 to 400 rpm, and top speed remained 19mph with 2 adults and Barley.

 

[steelespike]

The rpm should hold up better as you add weight.May improve loaded performance slightly.