Recommended RPM @ WOT for 83' 70hp Johnson

[Challenger84]

I just installed a tach for my OB (83' 70hp Johnson) and would like to know the recommended RPM range I should be at WOT.
I've read on here that these motors can rev from 4k-6k.
But I never read anything particular to my OB

If anyone can help that would be great!
Thanks
Happy boating!

 

[Challenger84]

Re: Recommended RPM @ WOT for 83' 70hp Johnson

bump

 

[trendsetter240]

Re: Recommended RPM @ WOT for 83' 70hp Johnson

5000 to 6000 RPM. You should setup with a prop that allows 5800-6000RPM at WOT with an average load.

 

[Challenger84]

Re: Recommended RPM @ WOT for 83' 70hp Johnson

thanks for the response!
I have two props that came with the boat and I'm trying to find out which one works best for me!
I'll get back with detail

 

[gsrsol84mm]

Re: Recommended RPM @ WOT for 83' 70hp Johnson

It would be great to know which props you have and the RPM range. I have a 1967 15' Dixie Tri Hull with a 1998 70 Johnson that I want to prop out. I have to first install a tach. ( Hope to do it next week )
What size boat do you have ?
Looking forward to seeing your results.

 

[Challenger84]

Re: Recommended RPM @ WOT for 83' 70hp Johnson

I have an 83' 70hp Johnson on a Charger 1600 which is 16' bow-rider. Weighs in at 750lbs.

So I changed out my prop to the 15' from 17'
@ WOT rpm was 5340-5420
with a total of 4 adults onboard and 6 gallons of fuel, and bimini UP!
I didn't get to pull any tubers today, just a test drive and to enjoy the weather!
Hope that helps!

 

[Challenger84]

Re: Recommended RPM @ WOT for 83' 70hp Johnson

It wasn't as fast as the 17' prop but got on plane as soon as I gave the throttle a little push forward.

 

[mmurray70]

Re: Recommended RPM @ WOT for 83' 70hp Johnson

I have a 1992 65 hp pushing a heavy 20ft boat. Just the boat alone is about1200lb. Id say total weight of boat/motor passengers and gear is around 2000lb. Anybody have any idea what kind of prop i should be running?

Right now it has a 13.75 x 15. I just had it in the water once to do a quick test on the engine (wasnt running when i bought it) and it seems to run ok but doesnt sound like its revving high enough. Just installed a tach this weekend so should get a better idea soon.