wierd tach issue

[bob johnson]

I have a red ( i believe OMC) tach and it is hooked up via the 8 pin connector from my johnson motor harness.

when i first wired it up it worked fine on the muffs( ran up to about 2000 rpm only)

then when i put the boat in the water the tach worked at first , and i noticed i think it going to about 3000...but next time i looked it wasnt working.

a few days later at home I put the muff on the engine and ran her and the tach was working again..

I wired another tach since the motor harness had a second set of wires for a non 8 pin tach.. and I had them both working.

then yesterday on the water the second tach wasnt working at all and the main tach was working but when under power the tach ran with the rpms up to aboput 2000 and then the needle fell back down to about 1000 rpms...even though the motors rpms continued to go up to at least 4000!!

slow down and the tach seemed to respond and correlate to the engine but throttle her up and the tach said UNCLE at 2000 rpms again...

funny thing is when i put the engine in nuetral and rev it..the tach ran up past 3000!!!!!( as far as i dared to rev in nuetral!)

why under power is the tach acting funky??

I am desperately trying to figure what my WOT rpms are!!!!

i seem to be going slower at top end than I should

thanks

bob

 

[Daviet]

Re: wierd tach issue

What year and model motor are we working on, can you give us the model number?

 

[bob johnson]

Re: wierd tach issue

What year and model motor are we working on, can you give us the model number?

the motor is a 1997 Evinrude 90 HP Ocean Pro

E90SLEUA

it has the OIS ignition system and is a V4 60 degree looper motor

bob

 

[bob johnson]

Re: wierd tach issue

anyone got any ideas????



bob