1976 70hp RPM's ?

[xtraham]

I have 1976 Johnson on a 16' AMF Crestliner I just installed a teliflex tach, on the id plate it says operating range 4500-5500 rpm motor has 13 1/4" X 17" prop with my son and myself in the boat (450#'s) tach says it is turning 5000 rpm's. @ idle tach shows 1000 rpm's I have been an auto truck tech for 30 years and to me it does not sound like the motor is idling more than about 600 rpm's how can I check this? I have an inductive pickup snap-on digital timming light that will show rpm's on automotive engines will it work on this 3 cyl outboard? Thanks in advance.........

 

[rickdb1boat]

Re: 1976 70hp RPM's ?

Did you set the dial on the back of the Tach. to the "6" position?

 

[xtraham]

Re: 1976 70hp RPM's ?

yes set @ 6

 

[xtraham]

Re: 1976 70hp RPM's ?

??

 

[Rancherlee]

Re: 1976 70hp RPM's ?

yes your snapon will work BUT the RPM's will show double what they really are since it fires every rotation of the enigine instead of every other like a car does. 1000rpm idle isn't bad either, I would be very suprised if it idle clean at 600rpm without popping and sputtering every so often (unless it has had boyesen reeds installed)

 

[xtraham]

Re: 1976 70hp RPM's ?

Thanks, I will hook up the light and check by 1/2.

 

[xtraham]

Re: 1976 70hp RPM's ?

thanks gent's hooked up digital light today boat tach was reading 1000 rpm's, snap-on tach bouncing 1950/2000 rpm's so i guess tach does not need calibrating, so i am cranked out @ about 5000/5100 rpm's would like to see 5400 rpm's, play with trim and wheels tomorrow thanks again...