tachometer?

[jonnymarquis]

have a 1977 70 hp evinrude. i need to know if any tach will work? i found one at part store for 30 deer but noticed it said will work with all 4,6,8 cylinder motors but mine is a 3 cyl. so just want a cheap tach to install for this motor will any tach work?

 

[DargelJohn]

Re: tachometer?

It actually depends on how many magnets you have in the flywheel. Sometimes you will see countersunk screwheads around the top of the flywheel. Each screwhead is a magnet.

On the back of the tach, there should be a screw for different pulse settings.
Take the number of magnets and divide by 2, and that is the pulse setting. I have a Johnson 88SPL which has 12 magnets, so my tach setting P6. My previous motor was an Evinrude 60 and it had 8 magnets (Setting P4).

 

[jonnymarquis]

Re: tachometer?

im a little confused here on this pic are you talking about blue red or yellow? if its yellow i cant really tell. but i think there is three. or maybe four. its hard to tell.

 

[DargelJohn]

Re: tachometer?

View attachment 85397 im a little confused here on this pic are you talking about blue red or yellow? if its yellow i cant really tell. but i think there is three. or maybe four. its hard to tell.

It's the Red arrow...

 

[Silvertip]

Re: tachometer?

Double posting is a no-no sir. No need for it. See my comments in your other thread. But to answer you again -- you are looking at an automobile tach which won't work on your engine.

 

[jonnymarquis]

Re: tachometer?

so i see 12 holes total if I'm correct that's 12? magnets. so 6P?

 

[DargelJohn]

Re: tachometer?

Yes, Make sure the "marine tach" you are buying has a P6 or 6 setting.

 

[jonnymarquis]

Re: tachometer?

ok so i was looking at an automobile tach, and that silver told me wont work so I'm so confused what to buy i see outboard tachs and tiny tachs but i read into them and i see 4,6,8 cylinders. so can you point me in the right direction where to buy and what to buy?

 

[DargelJohn]

Re: tachometer?

Do you have Academy, Bass Pro or other Outdoor stores in your area? What you need is a Teleflex Tach. They have an economy line of tachs that are reasonably priced. Good Luck

 

[jonnymarquis]

Re: tachometer?

well the closest is BPS and it still an hour and a half away. but i did do a check with a local boat shop and they have used ones for 15 so i guess ill go with that. thank you for the help.

 

[jonnymarquis]

Re: tachometer?

ok i hooked it up and it did not work. i was curious when i got it it was stuck on about 5k, it did move when wiggled, but i am wondering if a tach should be on 5k when not hooked up to anything? anyway i do have voltage on that gray wire when the motors running. so i don't think its with the wiring. i also hooked the red and black to 12 volts. so i think i just got a dud. he said if it didn't work i could bring it back and get another so i guess i will. anyway does that sound right about that tach? so i know what to look for when i go back. ty guys!

 

[boobie]

Re: tachometer?

Dargel, I've never heard of an OMC product with 8 magnets in the flywheel. Please explain.

 

[jonnymarquis]

Re: tachometer?

ok? so my motor's tach should be set to 6 right?

 

[eavega]

Re: tachometer?

ok? so my motor's tach should be set to 6 right?

Yes, I have a '76 70 HP Johnson, and the tach setting is 6.

 

[DargelJohn]

Re: tachometer?

Dargel, I've never heard of an OMC product with 8 magnets in the flywheel. Please explain.

Maybe it wasn't 8 magnets, but it definitely had a different setting than my 88SPL.

 

[DargelJohn]

Re: tachometer?

ok i hooked it up and it did not work. i was curious when i got it it was stuck on about 5k, it did move when wiggled, but i am wondering if a tach should be on 5k when not hooked up to anything? anyway i do have voltage on that gray wire when the motors running. so i don't think its with the wiring. i also hooked the red and black to 12 volts. so i think i just got a dud. he said if it didn't work i could bring it back and get another so i guess i will. anyway does that sound right about that tach? so i know what to look for when i go back. ty guys!

jonny, The you need to connect three wires: Purple - Ignition wire (+), Black - Negative (-) and the Gray - Pulse signal. It's not unusual for the tach to be sitting at 5K. When you turn on the ignition, it should jump back to zero.

 

[DargelJohn]

Re: tachometer?

Dargel, I've never heard of an OMC product with 8 magnets in the flywheel. Please explain.

My old Evinrude 60 had 10 magnets (5P). Sorry for the bad info.

 

[jonnymarquis]

Re: tachometer?

i hooked it strait to 12 v and grey wire just to test it before i cut into wires and drilled holes. but it didn't move.

 

[DargelJohn]

Re: tachometer?

The Purple, Black and Gray wires should be on the tag end of the wiring harness for the controls. I would wire it up correctly and give it a try; wait to drill the hole.

Purple to the Ignition or Positive post.
Black to the Ground post.
Gray to the Tach or Pulse post.

 

[boobie]

Re: tachometer?

Thank you Dargel for the correction. I knew better but didn't want to see somebody else on the forum get confused.