'79 johnson 115 max rpms

[david_r]

ok heres the deal---

old tach read 5200 new tach reads 5000 rpms......what gives?

i looked through my book to find the max rpm range and could only find the test wheel recomendations-----4800 rpm.

ran a search and found one guy that had been turning 6200 rpm .

what should my max rpm be?

what is the best rpm to set my timing at?

all wires and rectifier tested good......maybe old tach was crappy.

 

[ezeke]

Re: '79 johnson 115 max rpms

Most tachometers will read differently at different ranges of RPM.

You can use a technicians tachometer to compare the relative accuracy of your new tachometer in various ranges.

The 4800 RPM in the manual is the test RPM for that specific motor using that specific test wheel (#384933)

The full throttle operating range for your motor is listed as 4500 to 5500 RPM. The proper setup is at the top of the range or slightly higher at WOT.

 

[david_r]

Re: '79 johnson 115 max rpms

thanks ezeke.

so when i get ready to hang off the back of my boat again to check the timing 5400 will be good for the 28 btdc? or you think i shoulod go with 5500 and then turn down the wot to 5400 after i set up the max advance? i just did joe reeves wot timing last weak.........yeah i like to tinker with it even when something isnt wrong-------i know i know..........if it aint broke dont fix it........ or is it fix it till it is?!

i just chalked up the difference from old to new as maybe high resistance in the 1979 tach wires or windings........at least it looks that old. i havent seen gauges like that in forever.

 

[ezeke]

Re: '79 johnson 115 max rpms

My suggestion is that if you want to go beyond what Mr. Reeves has suggested, you should find someone who has a test tank and the proper test wheel to set your timing correctly.

The service manual for your model says to set the maximum spark advance at 4300 to 4600 rpm in gear (page 2-18)

 

[david_r]

Re: '79 johnson 115 max rpms

well the reason i was asking was because the last time i did joes setting i put it on the water ran wo and the rpm was 5500 and i was 1 degree off---possibly human error during my procedure.

now my tachs read different and was just curious as to waht the actual max rpm was supposed to be, and if my first set-up was right due to tach diff and maybe not my error.......especially after running a search and seeing so many different rpms on motors of the same year/model. i hardly ever run wo unless its for a short distance, usually just cruise.

i just kind of skimmed through my manual looking for specs......but it seems like these manuals are like the ones for cars-----they are no comparison to the dealers manuals.......although i do have a real manual, not the one for every yr/hp ever made, on my christmas list the wife thinks thats a lot of money for a book---probably have to buy it for myself.

 

[ezeke]

Re: '79 johnson 115 max rpms

David, you have to get used to chasing the used factory manuals down on Ebay or go broke. They all look like hell after a rebuild and a rainstorm.

Save a search for "1979 service 115"; at least one will come up and it does not matter if it is Johnson or Evinrude.

The 1979 manuals cover the 85, 115 and 140, so try each horsepower rating as well.

 

[david_r]

Re: '79 johnson 115 max rpms

thanks ezeke!

ill look into it.