3.0 mercuiser Alpha drive tach issue

[jdejongh]

Was doing a tune up on my 3.0 litre this weekend and when checking timing i noticed that my handheld tach was 900 rpm off from my console tach. We verified that the handheld was correct by trying another handheld my friend has. So im a bit stumped as to why my console tach reads so high. I see the sender wire goes to the neg side of coil. If the coil was the problem wouldnt i have starting and running issues too? Do tachs sometimes go bad?

thank you for your input

 

[mariner1900]

Re: 3.0 mercuiser Alpha drive tach issue

Yes tachos, like any meter, can fail. Typically the movement fails due to vibration and/or corrosion.

Does the tacho return to zero when you turn the key to on?

 

[jdejongh]

Re: 3.0 mercuiser Alpha drive tach issue

yes the tach returns to zero when off

 

[Bondo]

Re: 3.0 mercuiser Alpha drive tach issue

Do tachs sometimes go bad?

Ayuh,... They sure Do,... Quite often...