looking for the right prop.

[rbtlr]

I own a 1988 16 ft. deep V Lowe Lunker II bass boat with a 1988 Johnson 40 hp. motor model # J40 TEL CCS. Can anyone tell me what the factory pitch and size prop that the boat came with. It currently has a 11.75 x 17 pitch. prop on it now and I wanted to know if a 11.75 x 13 pitch would be running the rpms to high or what? range is 4500 - 5500 r.p.m. Any suggestions on what size and pitch for this particular boat to achieve the best performance.
Thanks. Richard

 

[steelespike]

Re: looking for the right prop.

Not knowing your present max rpm and speed its diffucult to say what prop is best.You shouldn't make any changes without knowing these specs.
depending on the weight of your boat and your typical load off the top of my head I would say the 17 is too much prop.But again without any specs really can't make any informed suggestions.Going to a 13 will increase rpm by about 800.

 

[jamieat]

Re: looking for the right prop.

You are definately going to need to know what your max RPM's are currently. That is the only way you are going to be able to make the right decision on what prop will best suit your current setup. If your max RPM range is 45-5500 then you are going to want to be able to turn your current prop 5500 or better. If you are not acheiving max RPM's, then you would go down in pitch, 1 pitch=approx 200 RPM's. So, just say you were turning your current prop 5000 RPM for instance, then you would want to drop pitch about 3 pitch sizes. Good Luck!!

 

[rbtlr]

Re: looking for the right prop.

Thanks fro the information. The rpm range for the motor is 4500-5500. I need to try and find out what my gear box ratio for this motor is and try and plug it in a prop calculator and see what it may come up with. I have a Tach on the boat but I am not sure how accurate it is so I may need to spend some money to get it checked out. But i was hoping someone may have the same setup and could tell me. It currently reads at around 3600 rpm wide open.
Thanks again.
Richard

 

[steelespike]

Re: looking for the right prop.

You might be able to borrow a shop tach or get a tech to go with you to compare readings to your tach.