Tach issues

[Nheels]

Sorry if this is in the wrong section, but figured this issue will primarily be electrical.

All,

I'm having some tach issues.

Port goes between 700-2000.
Starboard stays at 200ish.

Both are recording hours.

Motors: Volvo Penta 5.7L GI-300-J.

I believe the tach gets signal from the ignition coil via the gray wire. My plan was to check the wiring connector at the ignition coil for any obvious corrosion. Probably clean them out a bit, throw some dielectric grease on that connector and move on. I have a multimeter, but not with leads long enough to do a continuity test.

I'd then check the connections at the tachs for same.

Maybe these are symptoms of a bad ground? I'm hoping not as tracking down where those wires eventually meet up is going to be near impossible.

Any help would be appreciated!

 

[04fxdwgi25]

On the back of the tach is a hole with the adjustment in it for setting the number of cylinders of the engine. Move that adjustment from right stop to left stop a few times. Then set it back to proper setting of "8".

It is a switch in there that gets corrosion on the contacts after a while and swiping back and forth cleans them up.

 

[dubs283]

It's a gentle rap, like with a kid

Once, with light authority. I use my flashlight (with electrical tape on the butt, it cushions said blow and is easy on the teeth)

Pretty common to see the tach jump a bit after this performance

 

[Nheels]

It's a gentle rap, like with a kid

Once, with light authority. I use my flashlight (with electrical tape on the butt, it cushions said blow and is easy on the teeth)

Pretty common to see the tach jump a bit after this performance

Well I'll give that a shot too!

 

[04fxdwgi25]

It's a gentle rap, like with a kid

Once, with light authority. I use my flashlight (with electrical tape on the butt, it cushions said blow and is easy on the teeth)

Pretty common to see the tach jump a bit after this performance

I would suggest smacking it with a hammer as the last resort.

 

[dubs283]

Violence is not necessary, as my description utilizes a light rap with the taped end of the flashlight

It's a boat, at times patience is required for proper operation/diagnosis