70hp yamaha 17 or 19 pitch prop

[snooking99]

Ok I have a 1977 aquasport with a 2004 Yamaha 70hp 2 stroke with a 17 pitch prop that tops out at 28-29 mph. The boat use to have a 1978 70hp e rude and it ran 35-37 mph. I do not know what pitch prop was on the motor. Would that old engine just have more torque or maybe a 19 pitch prop? Anyways with the 17 pitch prop i turn 5400 rpm's trimmed out. From what I have read a 19 pitch would drop me roughly 200 rpm's but would I pick up more mph? The engine max operating range is 5000-6000.
Any help would be greatly appreciated. The engine is also on a 6" set back jackplate.

 

[Bifflefan]

Re: 70hp yamaha 17 or 19 pitch prop

the 19 will drop the rpms at the same speed or give more speed at the same rpm. I sounds as if the 19 will help but a 21 may do better (kills your hole shot).
does it feel like your out of power at the top or is the rpm just toppiong out like you in low gear in your car?
I dont remember what year you old motor was but my 74 johnny came with a 12.75x21. To fast for me.

 

[snooking99]

Re: 70hp yamaha 17 or 19 pitch prop

It seems like there not a big difference in speed when i jump from 4800 to 5400

 

[snooking99]

Re: 70hp yamaha 17 or 19 pitch prop

If someone can help me out with this soon I would appreciate it. I am currently bidding on a 19 on ebay.