70hp Yamaha Rpm Range

[cpopper81]

I have a 06 70 hp yamaha 2 stroke with a rpm range of 5000-6000 on a 17ft cape craft cc. at wide open throttle the motor only turns about 2800 rpm. do i need a smaller prop or pitch to get to the rpm range? the boat will only do about 41 mph with the current prop(don't know exact size,but came with motor,think its 14" diameter).any suggestions?

 

[rodbolt]

Re: 70hp Yamaha Rpm Range

did it ever turn up? did the tach get correctly setup?
call yamaha with your primary ID and see what the Pre Delivery Inspection sheet says.
if the tach is correctly set then install test wheel YB1620, shuold sww 5250-5450 RPM.
I suspect the tach is still set,4 stroke,2 wire trim and 12 pole if its a yamaha digital and 12 pole 6 pulse if aftermarket.
your needs to be set for 6 pole 3 pulse.
no way your running even close to 41 at 2800 just aint gonna do it ever.

 

[cpopper81]

Re: 70hp Yamaha Rpm Range

now that you mention it that doesn't make sense to run 41mph at 2800rpm's.I'll have to get somebody to check that out.thanks for the info.it's a mech. tach. by yamaha. it's never turned up more than that.

 

[rodbolt]

Re: 70hp Yamaha Rpm Range

was this a professional install or a shade tree out the backdoor type thing?
does a PDI sheet actually exist ?
does the tach have the overtemp and low oil visual indicates ?

 

[cpopper81]

Re: 70hp Yamaha Rpm Range

It was suppose to be a professional install. i bought the bought package deal from washington marine and sporting center in washington,nc.no visual alarms,just audible alarms. i'll have to take it back to them and let them fix there screw ups. i never really paid much att. to any of it cause with my job im not home much , so the boat sits in the yard the majority of the time. probaly doesn't have 100hrs on it.don't know why i didn't figure this out sooner, but the old two strokes i have owned were much louder than this one.