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ctuck0659 08-14-2004 06:21 PM
Merc 502 MPI Tach bounce
 
One of my engines has a bounce in the tach at idle up to about 2500 RPM. I don't detect a miss and it doesn't seem to effect performance. Mechanic scanned it- no codes, compression OK, changed to plugs- still there. Any ideas?

OldSchool 08-14-2004 06:29 PM
Re: Merc 502 MPI Tach bounce
 
Check your electrical connections

ctuck0659 08-14-2004 07:08 PM
Re: Merc 502 MPI Tach bounce
 
Thought about that- easier said than done of course but hopefully that's all it is-

ctuck0659 08-15-2004 06:26 PM
Re: Merc 502 MPI Tach bounce
 
gaffrig

ctuck0659 08-16-2004 05:00 PM
Re: Merc 502 MPI Tach bounce
 
Thanks- I'll start there...

US1 Fountain 08-16-2004 07:58 PM
Re: Merc 502 MPI Tach bounce
 
I had exact same symptons a couple yrs ago. Removed and cleaned the wire connections on the back of the tach and also flipped the 4-6-8 selector switch several times. Solved my tach bounce.

Excalibur502mag 08-16-2004 10:59 PM
Re: Merc 502 MPI Tach bounce
 
I am having the same problem. Please let me know what you find out.
US1, could you please explain what the 4-6-8 selector switch is?

GLH 08-17-2004 06:31 AM
Re: Merc 502 MPI Tach bounce
 
Short or bad ground somewhere

US1 Fountain 08-17-2004 07:07 AM
Re: Merc 502 MPI Tach bounce
 
Originally Posted by Excalibur502mag
I am having the same problem. Please let me know what you find out.
US1, could you please explain what the 4-6-8 selector switch is?
A switch on the back of the tach that corresponds with the # of cyls. your motor has.


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